Maria Melchior
email: maria.melchior@inserm.fr

Natasha Figueiredo

Aurélia Roversi

Alexandre Dubanchet

Eric Bui

Julian Vadell-Martínez

Corrado Barbui

Marianna Purgato

José Luis

Roberto Mediavilla

José Luis Ayuso- Mateos

David Mcdaid

A-La Park

Papoula Petri-Romão

Raffael Kalisch

Pablo Nicaise

Vincent Lorant

Marit Sijbrandij

Anke B Witteveen

Richard Bryant

Mireia Felez

James Underhill

Giulia Pollice

Andrea Tortelli

Addressing mental health problems among persons without stable housing in the context of the COVID-19 pandemic: study

Keywords: Randomized Controlled Trial, Psychological Distress, COVID-19, Housing Instability, Migrant, Doing What Matters in Times of Stress, Problem Management Plus, Economic Evaluation, France 3610, Figure: 1, Table: 2, Supplementary Table

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Background

The COVID-19 pandemic has contributed to a worldwide increase in the prevalence of psychological distress and symptoms of anxiety and depression, (1) although this has recently been a matter of some debate, in part due to heterogeneity in findings across different stages of the sanitary crisis. [START_REF] Witteveen | COVID-19 and common mental health symptoms in the early phase of the pandemic: An umbrella review of the evidence[END_REF] While in the general population the increase in mental health problems was observed in 2020 and appears to have decreased afterwards, this may not be the case in marginalized groups. In particular, research has highlighted a high prevalence of mental health problems among individuals experiencing socioeconomic disadvantage compared to the general population. [START_REF] Wang | Factors associated with psychological distress during the coronavirus disease 2019 (COVID-19) pandemic on the predominantly general population: A systematic review and meta-analysis[END_REF][START_REF] Camara | COVID-19related mental health difficulties among marginalised populations: A literature review[END_REF] Mental health care systems are thus facing difficulties in addressing this growing demand , which may result in delays or unmet needs, increasing existing social inequalities in mental health and health care access. [START_REF] Stevens | The experiences of socially vulnerable groups in England during the COVID-19 pandemic: A rapid health needs assessment[END_REF] In France in recent years, and more particularly in the Paris area, there has been an increase in the number of people who are homeless, sleeping rough or experience unstable housing conditions, among whom a large proportion are recent migrants and asylum seekers due in part to changes in migratory patterns and asylum regulations which contribute to newcomers' social vulnerability [START_REF] Roze | Factors associated with depression among homeless mothers. Results of the ENFAMS survey[END_REF]. In addition to social disadvantage, this group often experiences violence, discrimination, and isolation, as well as cultural and language barriers before, during and after migration, [START_REF] Campion | Inequality and mental disorders: opportunities for action[END_REF] and should have priority in terms of prevention of health conditions and treatment. However, this group experiences widely documented unmet needs in terms of mental health care. The COVID-19 pandemic has resulted in increased difficulties in accessing mental health care at large and in marginalized populations, calling for the evaluation of new scalable psychosocial interventions.

To make mental health care accessible, it is necessary to adapt it. For that purpose, the World Health Organization (WHO) has developed a number of scalable psychological interventions based on Acceptance and Commitment Therapy (ACT) including Doing What Matters in Times of Stress (DWM) [START_REF] Organization | Doing what matters in times of stress[END_REF] and Problem Management Plus (PM+) [START_REF]Problem Management Plus (PM+): Individual psychological health for adults impaired by distress in communities exposed to adversity[END_REF]. DWM is a self-help stress management guide that includes pre-recorded audio exercises and illustrations, introducing participants to five different strategies to relieve stress (e.g. mindfulness exercises) and has been shown to reduce psychological distress across multiple trials [START_REF] Acarturk | Effectiveness of a WHO self-help psychological intervention for preventing mental disorders among Syrian refugees in Turkey: a randomized controlled trial[END_REF][START_REF] Tol | Guided self-help to reduce psychological distress in South Sudanese female refugees in Uganda: a cluster randomised trial[END_REF]. To be widely accessible, DWM has been adapted for individual use as a mobile-supported website with distance support by a trained person spread over the course of 5 weeks. Self-Help + (SH+), is an intervention based on the DMW manual. The PM+ intervention is based on principles of Cognitive Behavioural Therapy (CBT) and Problem-Solving Therapy and can be delivered by non-specialists in situations where mental health care is not accessible. PM+ has four core features: it is brief (five sessions); delivered by non-specialist helpers; transdiagnostic (it addresses depression, anxiety, post-traumatic stress disorder, psychological distress); it was originally designed for individuals living in communities with limited mental health care resources but is easily adaptable to different populations, cultures and languages. Organised in 5 sessions, PM+ can be delivered individually or in groups of adults experiencing distress to help them develop problem management strategies. Both individual and group formats of PM+ have been shown to reduce anxiety and depression [START_REF] Bryant | Effectiveness of a brief group behavioral intervention for common mental disorders in Syrian refugees in Jordan: A randomized controlled trial[END_REF][START_REF] Rahman | Effectiveness of a brief group psychological intervention for women in a post-conflict setting in Pakistan: a single-blind, cluster, randomised controlled trial[END_REF]. These interventions do not replace specialised mental health care for people with severe psychiatric disorders, but contribute to reducing psychological distress and decrease later risk of mental disorders among persons with mild to moderate manifestations.

The main aim of the present randomised controlled trial (RCT) is to evaluate the effectiveness of the stepped-care program combining DWM and PM+ to reduce symptoms of depression and anxiety amongst adults experiencing unstable housing in comparison to enhanced care-as-usual (eCAU). The secondary objectives are to evaluate: (a) the effect of the intervention on participants' quality of life and resilience; (b) the moderation of the effect of the intervention by participants' sociodemographic characteristics, living conditions, and experiences of trauma (i.e. individuals who have lower levels of education, less stable housing situation, and higher levels of trauma are expected to benefit less from the psychosocial program being tested); (c) the resource impacts and costeffectiveness of DWM and PM+ interventions. In France, a large proportion of individuals experiencing unstable housing conditions and sheltered in collective accommodation facilities are migrants [START_REF] Roze | Factors associated with depression among homeless mothers. Results of the ENFAMS survey[END_REF], therefore the DWM and PM+ protocols were professionally translated and back translated by study helpers who are native speakers and trained translators to languages most frequently spoken by recent asylum seekers and migrants to France (Dari and Pashto); we also used the existing Arabic translation provided by the WHO [START_REF] Guisao | F La santé des migrants primo-arrivants: résultats des bilans infirmiers réalisés d'octobre 2015 à mars 2016 dans des centres franciliens hébergeant des migrants évacués des campements parisiens[END_REF]. The study being conducted under the supervision of a psychiatrists (AT), the validity of the tools used to screen for psychological distress can be validated after the trial. PM+ was previously used in studies conducted across different parts of the world (for instance in Pakistan and among Syrian refugees to Jordan) [START_REF] Bryant | Effectiveness of a brief group behavioral intervention for common mental disorders in Syrian refugees in Jordan: A randomized controlled trial[END_REF][START_REF] Hamdani | Problem Management Plus (PM+) in the management of common mental disorders in a specialized mental healthcare facility in Pakistan; study protocol for a randomized controlled trial[END_REF]. Prior to the implementation of this randomised controlled trial, we conducted a pilot study in 2019-2020 to test the feasibility of recruiting participants for this intervention among people who do not speak French and reside in temporary accommodation. The pilot study allowed us to make a number of adjustments to study recruitment procedures (for instance the selection of participating accommodation centres) and research questionnaires, as well as estimate attrition. The present RCT is part of the Horizon 2020 cross-national RESPOND project (Australia, Belgium, France, Germany, Italy, Netherlands, Spain, Sweden and the United Kingdom) aiming to test effective ways of addressing population mental health needs following the COVID-19 pandemic [START_REF] Mediavilla | Effectiveness of a stepped-care programme of internet-based psychological interventions for healthcare workers with psychological distress: Study protocol for the RESPOND healthcare workers randomised controlled trial[END_REF][START_REF] Purgato | Effectiveness of a stepped-care programme of WHO psychological interventions in migrant populations resettled in Italy: Study protocol for the RESPOND randomized controlled trial[END_REF]. This protocol was not peer-reviewed as part of the funding process.

Methods: Participants, intervention and outcomes

Study setting

This study is set in the Paris and Caen regions in France, among people who experience unstable housing conditions (that is individuals who are homeless and are sheltered in temporary accommodation, by other people, or have no regular shelter) recruited via temporary accommodation centres as well as ambulatory care for people who experience social disadvantage and/or are migrant. The Paris region traditionally attracts new migrants because it concentrates economic resources. As a result, it a region where many infrastructures serve migrants -particularly those experiencing social disadvantage, making recruitment easier. As for Caen, it has also become an area concentrating migrants, due to its proximity to the UK. Moreover, one of the study's collaborators (Dr. Bui) is based in Caen. We acknowledge that the selection of study locations may be a limitation of the protocol.

Eligibility criteria

Individuals will be able to participate in the trial if they are 18 years of age or older, have elevated levels of psychological distress as assessed with the Kessler-10 scale (K10 score ≥15.9) [START_REF] Kessler | Short screening scales to monitor population prevalences and trends in non-specific psychological distress[END_REF], speak one of the study languages (Arabic, Dari, French, Pashto), find themselves without stable housing and are willing to participate.

Exclusion criteria include having an acute medical or psychiatric condition requiring urgent medical attention (e.g. hospitalization) as ascertained by the consultant psychiatrist involved in the trial (Dr. AT), a high risk of suicide, moderate/severe cognitive impairment (e.g. severe intellectual disability or dementia), being under legal protection (guardianship, curatorship, safeguard of justice), a change in the level of psychotropic treatment in the two months preceding the trial (as ascertained in the baseline study questionnaire at T1), and refusal to participate.

Interventions

This is a randomized controlled study, comparing a stepped-care intervention to enhanced Care as Usual (all participants will receive Psychological First Aid, PFA, prior to treatment allocation). All study assessments and interventions are described in Figure1. Participants randomly allocated to the intervention arm through the electronic platform used to collect study data will first receive the DWM intervention for 5 weeks (weeks 2 to 6). At the end of the DWM intervention, participants will complete the first follow-up questionnaire (T2 -week 7), which includes the K10 scale to evaluate whether they still experience high levels of psychological distress (K10 score ≥15.9). If so, they will receive the PM+ intervention for the next 5 weeks (weeks 8 to 12) and then answer the second follow up questionnaire (T3 -week 13). Otherwise, they will skip the PM+ intervention and only complete a follow-up questionnaire at week 13. Two months later, participants will complete the last follow-up questionnaire (T4 -week 21).

Participants allocated to the control group will complete the study questionnaires (T1, T2, T3 and T4) at the same time points as the intervention group and will not receive the DWM/PM+ stepped-care program. The control group consists of enhanced Care as Usual, as participants receive Psychological First Aid (PFA) in addition to standard treatment.

1. Psychological First Aid (PFA) is a support strategy that involves humane, supportive and practical help for individuals experiencing a serious collective crisis [START_REF] Hobfoll | Five essential elements of immediate and mid-term mass trauma intervention: empirical evidence[END_REF] delivered to all study participants in both trial arms. PFA consists of a conversation (approximately 30-45 minutes) which can be provided remotely (e.g. videoconferencing or telephone). This conversation has various themes; non-intruding practical care and support, description of mental health needs and concerns, information about ways of addressing individuals' basic needs, provision of comfort and help staying calm, help connecting to services and social support, as well as protection of individuals from further harm [START_REF] Organization | Psychological first aid[END_REF]. In this study, DWM will be delivered online, via a web-based program designed to be used on a smartphone with the assistance of a helper. Helper support will be flexible, and on average occur once a week for approximately 15-20 minutes. Every week over the course of five weeks, a new module will be unlocked.

Problem Management + (PM+) is a brief, psychological intervention based on cognitive

behavioural therapy (CBT) techniques that are empirically supported, formally recommended and developed by the WHO. The manual involves the following empirically supported elements: problem solving, stress management, behavioural activation, and accessing social support. In 60-minute sessions, participants talk to trained non-professional helpers. PM+ sessions will be conducted faceto-face by a helper, also over a five-week period at a rate of one session per week.

The cultural acceptability of DMW and PM+ among potential study participants and social workers attending to their needs was verified in qualitative research prior to study inception.

For both DWM and PM+, manuals can be accessed online [START_REF] Organization | Doing what matters in times of stress[END_REF][START_REF]Problem Management Plus (PM+): Individual psychological health for adults impaired by distress in communities exposed to adversity[END_REF].

Figure 1. Framework of the RESPOND trial -France

The primary study outcome is the Patient Health Questionnaire-Anxiety and Depression Score (PHQ-ADS), a sum of scores on the Patient Health Questionnaire-9 (PHQ-9) and the Generalized Anxiety Disorder -7 (GAD-7), two scales evaluating respectively symptoms of depression and of generalised anxiety disorder [START_REF] Kroenke | Patient Health Questionnaire Anxiety and Depression Scale: Initial validation in three clinical trials[END_REF][START_REF] Kroenke | Comparative validity and responsiveness of PHQ-ADS and other composite anxiety-depression measures[END_REF]. The PHQ-9 includes 9 items and the GAD-7 comprises 7 items, the combined score ranging from 0 to 48. Elevated scores indicate a higher level of symptoms of depression and anxiety. Two validation studies of the PHQ-ADS among patients with chronic pain and cancers have been summarized and published [START_REF] Kroenke | Comparative validity and responsiveness of PHQ-ADS and other composite anxiety-depression measures[END_REF]. This score has strong internal reliability (Cronbach's alpha of 0.8 and 0.9), strong convergent validity, sufficient uni-dimensionality and is sensitive to change.

As secondary study outcomes, we will use the PHQ-9 alone( 23), the GAD-7 alone [START_REF] Spitzer | A brief measure for assessing generalized anxiety disorder: the GAD-7[END_REF], as well as other measures of participants' mental health: the Patient Checklist-5 (PCL-5) assessing symptoms of Post-Traumatic Stress Disorder [START_REF] Ashbaugh | Psychometric validation of the English and French versions of the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5)[END_REF], Psychotic Symptoms assessed using the MINI questionnaire [START_REF] Sheehan | The Mini-International Neuropsychiatric Interview (M.I.N.I.): the development and validation of a structured diagnostic psychiatric interview for DSM-IV and ICD-10[END_REF] and quality of life assessed using the EQ-5D-5L [START_REF] Herdman | Development and preliminary testing of the new five-level version of EQ-5D (EQ-5D-5L)[END_REF]. Additionally, we will assess outcome-based resilience, which is operationalised as the individual deviation from the sample-based normative stressor reactivity, that is a difference between individual-level observed and sample-based predicted values of psychological distress considering a certain number of stressors. Resilience will be calculated with a measure of stressor exposure which has been adapted from the Mainz Inventory of Microstressors (MIMIS) and the PHQ-9 and GAD-7 [START_REF] Kalisch | The Frequent Stressor and Mental Health Monitoring-Paradigm: A Proposal for the operationalization and measurement of resilience and the identification of resilience processes in longitudinal observational studies[END_REF].

Additionally, baseline and follow-up study questionnaires will ascertain participants' sociodemographic characteristics (sex, age, nationality, educational level, income, etc.), as well as COVID-19-related stressors (that is 11 items relative to worries regarding COVID-19 infection and possible stigma due to contamination, as well as loss of income, employment or basic life resources due to COVID-19 and possible administrative complications related to the sanitary crisis and its aftermath). Furthermore, participants are asked to report on their appraisal style using the Perceived Positive Appraisal Style Scale, content-focused version (PASSc) [START_REF] Kalisch | The Frequent Stressor and Mental Health Monitoring-Paradigm: A Proposal for the operationalization and measurement of resilience and the identification of resilience processes in longitudinal observational studies[END_REF]. Moreover participants' stress levels will be assessed using the Brief Trauma Questionnaire (BTQ) [START_REF] Weathers | The Clinician-Administered PTSD Scale for DSM-5 (CAPS-5): Development and initial psychometric evaluation in military veterans[END_REF]. Finally, cost-effectiveness of the intervention will also be examined.

Participant timeline

Each participant will be in the study for 21 weeks.

Sample size

Overall, 210 participants will be included. Based on previous studies of PM+ [START_REF] Rahman | Effect of a multicomponent behavioral intervention in adults impaired by psychological distress in a conflictaffected area of Pakistan: a Randomized Clinical Trial[END_REF][START_REF] Bryant | Effectiveness of a brief behavioural intervention on psychological distress among women with a history of gender-based violence in urban Kenya: A randomised clinical trial[END_REF], we aim to detect a small to medium effect size corresponding to a Cohen's d= 0.4 in the intervention group at 2 months, as measured with the PHQ-ADS and as compared to the control group. A calculation of statistical power for a repeated measures study design (mixed regression model), given incomplete participation in each of the planned assessments, suggests a minimum sample size of n=73 per group (power=0.80, alpha=0, 05, bilateral, rho=0.9). Considering an attrition rate of 30%, estimated based on a prior pilot study and past evaluations of PM+, we calculated a total number of 210 participants needed (105 in each group). If needed, missing data on study covariates will be handled using standard multiple imputation techniques.

Recruitment

Participants are recruited directly in temporary accommodation centres as well as ambulatory care for people experiencing social disadvantage and/or who are migrant, by trained helpers who are in contact with each site's coordinator and regularly visit to list potential participants and contact them.

Recruitment and allocation started in March 2022 and is should be completed by the end of October, 2023. The first post-allocation took place in July 2022 and the last one will take place in February 2024, study close-out should occur in February 2024. To enhance retention and reduce study dropout, participants are compensated 3*20 euros (at T1, T3 and T4). We also cover their travel expenses if they are interviewed on research premises rather than at the accommodation centre where they live.

Adverse events

Any undesirable experience occurring during the study, whether or not considered related to the trial procedure or the stepped-care DWM/PM+ program, will be considered an Adverse Event. All adverse events reported spontaneously by study participants or observed by the investigators will be recorded and reported to the promoting agency (ANRS-MIE).

Methods : Assignment of intervention

To evaluate the effectiveness and cost effectiveness of the DMW/PM+ stepped-care program, we will conduct an RCT comparing the DMW/PM+ stepped-care programme to enhanced care-as-usual (n=105 each), delivered after all participants receive psychological first aid (PFA). After verification of inclusion criteria, participants will be randomly allocated to the intervention or eCAU based on a 1:1 basis, via the Castor Electronic Data Capture web-based software, also used to collect study data.

This electronic tool applies a variable block randomization method, randomly permuting blocks of unequal size. The site investigators will be blind to the block size and will not have access to the randomization list.

Blinding of participants and data collectors to the intervention will not be possible due to the nature of the intervention being evaluated.

Methods : Data collection, management, analysis

A total of 210 participants will be recruited in two locations: Paris and Caen (Normandy, North Western France). In Paris, recruitment activities will be conducted via mental health care ambulatory services dedicated to migrants who experience social disadvantage (Precarity Unit of the GHU Paris, the largest psychiatric hospital in Paris), and accommodation centres for homeless people and asylum seekers. In Caen, participants will be recruited from accommodation centres for the homeless. Potential participants will be informed about the study and given one week to decide whether they want to enrol. Participants who accept to enrol in the study and sign the informed consent form will complete the study screening questionnaire, which includes the K10 scale screening for psychological distress, as well as measures of sociodemographic and health characteristics. Participants who meet all inclusion criteria will complete the first study questionnaire and will be randomly allocated to one of the two study groups: intervention (PFA, DWM and PM+ and CAU) or eCAU (PFA and CAU) (T1week 1).

Five helpers will be recruited to implement PFA, DWM and PM+ among study participants. All helpers will be specially trained by a Master trainer and supervised weekly by a clinical psychologist throughout the study.

Prior to the recruitment of the first study participant, qualitative research activities were implemented to better understand the perceptions and expectations of eligible individuals. Initial qualitative interviews were conducted with 22 potential study participants as well as 26 professionals working in temporary accommodation centres, who are key in identifying and referring potential study participants. These qualitative interviews made it possible to adapt the research tools (for example the wording used in DMW and research questionnaires), as well as assess the acceptability of the proposed research protocol. At the end of the project, qualitative interviews with study participants as well as social workers and other support staff, will collect participants' feedback and help gain information on ways of disseminating the program broadly.

Data collection methods

All study questionnaires (from T0 to T3) will be administered by a member of the research team or by a trained helper (Table 1). Face-to-face data collection will be prioritised but video or telephone meetings will be allowed if needed. Questionnaire administration and randomisation will be implemented using CASTOR EDC, an electronic CRF (eCRF). Table 2 describes the SPIRIT diagram for the schedule of enrolment, intervention and assessment.

Data management

Quantitative data obtained from study questionnaires being collected on an eCRF will be automatically stored electronically. Each participant will be identified with a unique numerical identifier, all personal data used to contact participants being stored separately and securely. In compliance with French regulations, all data will be stored for two years after the end of the trial. In case of adverse events, information will be systematically collected, forwarded to the promoting agency and if necessary participation will be stopped. The trial will be audited after completion.

Statistical methods

The data will be analysed using: (a) an intention-to-treat (ITT) analysis, which will include all participants recruited for the study (n=210); (b) an analysis among participants who complete the program (per protocol -PP). The statistical analyses will be masked, i.e. the trial statistician will be blind to the group allocation until the analysis is complete. In addition, the trial statistician will not be involved in participant eligibility determination, intervention administration, outcome measurement, or data entry.

To estimate the effect of the intervention, a linear mixed model will be used. The intervention will be included as a fixed effect, the subject as the random effect, the baseline score of the primary outcome as a covariate. A covariate-adjusted linear mixed model of the primary endpoint will also be implemented adding covariates pre-specified at study baseline (gender, age, education, COVID-19related events, and symptom severity, as well as pre-existing levels of depression and anxiety). The primary analysis will assess treatment effect on the average PHQ-ADS score at each time-point in the ITT population. The main conclusion of the trial will be drawn from this ITT analysis (i.e., the effect on PHQ-ADS score at the 2-month follow-up). In addition to the main analysis, secondary analyses will also be implemented. First, participants' levels of psychological distress (PM+), symptoms of posttraumatic stress disorder (PCL-5), and quality of life (EQ-5D-5L) will be evaluated at one-month post DWM (T2), as well as one week (T3) and two months post PM+ (T4). Second, changes in the number of cases of depression will be calculated in the PP sample using a logistic regression model.

Third, the role of perceived positive appraisal style as measured by PASSc in relation to the first and secondary outcomes will be explored. Fourth, outcome-based resilience will be examined using mental health symptoms against stressor exposure. All statistical analyses will be implemented using Rstudio.

which includes independent experts and relevant stakeholders. Protocol amendments will be notified to the Comité de Protection des Personnes and authorization will be sought.

Conclusion

Our study will test the effectiveness and cost-effectiveness of a stepped-care program including DWM and PM+, hypothesised to provide support to persons experiencing psychological distress and having difficulty accessing healthcare. Evidence suggests that stepped-care models are modestly effective [START_REF] Beecham | Costing psychiatric interventions[END_REF], although there is a high heterogeneity of such models (number of steps, duration of steps, rules about stepping up) and their effects, implying the need for further research.

Interestingly, there is also evidence that health care providers benefit from a switch from a matched care to a stepped-care approach [START_REF] Boyd | Impact of a progressive stepped care approach in an improving access to psychological therapies service: An observational study[END_REF]. Stepped-care interventions are both innovative and affordable since they can be administered face-to-face or remotely by non-professional helpers who receive special training. They could be particularly well-suited for people who experience social disadvantage, such as persons with an unstable housing situation and migrants, and face multiple barriers to access healthcare.

Overall, this study will contribute to identifying the impact of stepped-care programs on reducing psychological distress among marginalized populations who experience high levels of psychological distress yet have difficulty accessing mental health care. Results will contribute to providing effective community-based health care implementation strategies to scale-up the delivery and uptake of evidence-based mental health interventions in different contexts to address the specific needs. They will be disseminated to scientists, decisionmakers as well as study participants through dedicated publications and the Internet.

2 .

 2 Doing What Matters in times of stress (DWM) is a self-help stress management guide based on the principles of Acceptance and Commitment Therapy (ACT). DWM includes five sections, each of which focuses on a specific skill (Grounding; Unhooking; Acting on your values; Being kind; Making room).

Table 1 : Measures assessed in the RESPOND Randomised Trial France.

 1

	Measures

Table 2 : SPIRIT diagram for the schedule of enrolment, intervention and assessment in the RESPOND Randomised Trial France.

 2

				Study period
		Enrolment	Allocation DMW	Post allocation		Close-out
	Timepoint	T0	T1	T2	PM+	T3	T4
				(Week 7)	(Week 13)	(Week 21)
	Enrolment	x
	Information	x
	about the
	study
	Eligibility		x
	screen
	Informed		x
	consent
	Allocation		x
	Interventions		x
	Intervention		x
	group
	Control		x
	group
	Assessments		x	x		x	x

Acknowledgements

The authors wish to acknowledge WHO staff who have contributed to the development of Doing What Matters and Problem Management+, as well as ANRS-MIE staff who were involved in helping finalize the study protocol and obtain all necessary ethical and regulatory authorizations.

Funding

This study is embedded in the larger, EU Horizon 2020 H2020-SC1-PHE-CORONAVIRUS-2020-2 funded RESPOND (Improving the Preparedness of Health Systems to Reduce Mental Health and Psychosocial Concerns resulting from the COVID-19 Pandemic) project (Grant Agreement 101016127). The RESPOND project is composed of a consortium of eight countries: the Netherlands, France, Spain, Italy, Belgium, United Kingdom, Sweden, Australia. The funder has no influence in study design; collection, management, analysis, and interpretation of data; writing of the report; and the decision to submit the report for publication.

Availability of data and materials

Data collected in the RESPOND Project -France are available from the authors (maria.melchior@inserm.fr) upon reasonable request and with permission of INSERM|ANRS-MIE.

Study outcomes

Table 1 shows all the measures collected across study questionnaires (from T1 to T4).

Economic analysis

The primary outcome for the economic analysis will be the incremental costs per QALY gained between the intervention and comparator groups. The total costs of delivering interventions will be estimated and combined with data on changes in health service utilisation and time out of usual activity (from T1 to T4) obtained using a bespoke version of the Client Service Receipt Inventory (CSRI) [START_REF] Beecham | Costing psychiatric interventions[END_REF], an instrument widely used for the collection of self-report service utilisation. Unit costs will be defined depending on the type of resource used. In addition to using the CSRI, we will collate information on the resources and costs of implementing the intervention, including initial and ongoing training/supervision. EQ-5D-3L questionnaire responses from participants will be transformed into a preference-based index utility score using published French population tariffs [START_REF] Andrade | A French Value Set for the EQ-5D-5L[END_REF] and QALYs will be calculated using the area under the curve approach. The economic analysis will be conducted from both the health care system and societal perspectives. Between-group comparisons of mean costs will be undertaken using appropriate statistical tests depending on the type and distribution of data. Univariate sensitivity analyses and non-parametric bootstrapping will be used to account for uncertainty in trial parameters and cost effectiveness planes will be generated. Costeffectiveness acceptability curves will be constructed to indicate the likelihood that the intervention will be cost-effective at different levels of willingness to pay. The economic analysis will be conducted using STATA and SPSS.

Ethics and dissemination

This research has obtained the approval of the Ethics Committee "Île de France III" on July

Consent for publication

Our manuscript does not contain individual data, therefore this category does not apply.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

MM and AT conceived the study, coordinated its design, and drafted and wrote the manuscript. NF, AR, JV and EB participated in conceptualizing the study as well as writing the manuscript. All authors read and were involved in critical appraisal and revision of the manuscript and approved the final manuscript.


Laura Charlanne
email: laura.charlanne@iphc.cnrs.fr

Laureline Chaise

Damien Sornette

Erwan Piot

Dominic J Mccafferty

André Ancel

Caroline Gilbert

Breaking the fast: First report of dives and ingestion events in molting southern elephant seals

Southern elephant seals (SES) experience a 'catastrophic molt', a costly event characterized by the renewal of both hair and epidermis that requires high peripheral vascular circulation. Molting animals are therefore constrained by high metabolic heat loss and are thought to fast and remain on land.

To examine the ability of individuals to balance the energetic constraints of molting on land we investigate the stomach temperature and movement patterns of molting female SES.

We find that 79% of females swam and 61% ingested water or prey items, despite the cost of cold-water exposure while molting. This behavior was related to periods of warm and low wind conditions, and females that dived and ingested more often, lost less body mass.

We conclude that the paradigm of fasting during the molt in this species, and the fitness consequences of this behavior should be reconsidered, especially in the context of a changing climate.

Introduction

Molting is an important physiological event of partial or total renewal of integuments, which is influenced by season, growth, age, and environmental conditions [START_REF] Schmidt-Nielsen | How Animals Work[END_REF][START_REF] Bourlière | Animal Physiology-Adaptation and Environment[END_REF] . This process occurs in a large variety of species, including mammals [START_REF] Ling | Pelage and Molting in Wild Mammals with Special Reference to Aquatic Forms[END_REF][START_REF] Beltran | Convergence of biannual moulting strategies across birds and mammals[END_REF][START_REF] Zimova | Function and underlying mechanisms of seasonal colour moulting in mammals and birds: what keeps them changing in a warming world?[END_REF] , birds [START_REF] Zimova | Function and underlying mechanisms of seasonal colour moulting in mammals and birds: what keeps them changing in a warming world?[END_REF][START_REF] Kjellén | Moult in relation to migration in birds-a review[END_REF] , reptiles [START_REF] Hellebuyck | Dermatological diseases in lizards[END_REF][START_REF] Wheler | Skin Diseases of Exotic Pets[END_REF] ,fishes [START_REF] Newton | Moult and plumage[END_REF] and arthropods [START_REF] Ruppert | Invertebrate zoology: a functional evolutionary approach[END_REF] . Molting is involved with a change in coat or plumage color, that may be related to reproductive success and camouflage in the environment [START_REF] Zimova | Function and underlying mechanisms of seasonal colour moulting in mammals and birds: what keeps them changing in a warming world?[END_REF][START_REF] Valdez | Annual molt period and seasonal color variation in the Eared Dove´s crown[END_REF] , growth [START_REF] Ruppert | Invertebrate zoology: a functional evolutionary approach[END_REF] , thermoregulation [START_REF] Maurel | Seasonal moulting patterns in three fur bearing mammals: the European badger (Meles meles L.), the red fox (Vulpes vulpes L.), and the mink (Mustela vison). A morphological and histological study[END_REF] , and defense against parasites or pathogens 7 , hence playing an important role in the fitness of an individual. However, molt is an energy demanding process [START_REF] Zuberogoitia | Moult in Birds of Prey: A Review of Current Knowledge and Future Challenges for Research[END_REF] requiring high peripheral vascular circulation to promote skin cell proliferation and tissue growth [START_REF] Ashwell-Erickson | Metabolic and hormonal correlates of molting and regeneration of pelage in Alaskan harbor and spotted seals (Phoca vitulina and Phoca largha)[END_REF] , and a high metabolic rate to balance heat loss [START_REF] Walcott | Thermoregulatory costs in molting Antarctic Weddell seals: impacts of physiological and environmental conditions[END_REF][START_REF] Thometz | Maintaining control: metabolism of molting Arctic seals in water and when hauled out[END_REF] .

Most Antarctic and sub-Antarctic phocid seals undergo an annual molt [START_REF] Beltran | Convergence of biannual moulting strategies across birds and mammals[END_REF] . While seals are well adapted for an aquatic life, they are obliged to come ashore (on land or ice floe) to molt [START_REF] Boeuf | Sex differences in diving and foraging behaviour of northern elephant seals[END_REF][START_REF] Kooyman | Moult of the emperor penguin: travel, location, and habitat selection[END_REF] . In phocids, regrowth of skin and fur requires a skin temperature above 17°C [START_REF] Feltz | Thermal requirements in vitro of epidermal cells from seals[END_REF] . Maintenance of this warm temperature in polar regions leads to elevated metabolic rate [START_REF] Walcott | Thermoregulatory costs in molting Antarctic Weddell seals: impacts of physiological and environmental conditions[END_REF][START_REF] Thometz | Maintaining control: metabolism of molting Arctic seals in water and when hauled out[END_REF][START_REF] Kuhn | Time to eat: measurements of feeding behaviour in a large marine predator, the northern elephant seal Mirounga angustirostris[END_REF] . To reduce energy expenditure during the molt, seals are insulated with thick subcutaneous blubber [START_REF] Scholander | Body insulation of some arctic and tropical mammals and birds[END_REF][START_REF] Worthy | Moult energetics of the northern elephant seal (Mirounga angustirostris)[END_REF] , regulate peripheral blood flow, and avoid even higher heat loss by hauling out to minimize time in cold water, where heat loss is 25 times faster than in air [START_REF] Nadel | Energy exchanges in water[END_REF][START_REF] Paterson | Increased Metabolic Rate of Hauled-Out Harbor Seals ( Phoca vitulina ) during the Molt[END_REF] . Even with these actions, molting metabolic rate is 2-3 higher than resting metabolic rate [START_REF] Ashwell-Erickson | Metabolic and hormonal correlates of molting and regeneration of pelage in Alaskan harbor and spotted seals (Phoca vitulina and Phoca largha)[END_REF][START_REF] Paterson | Increased Metabolic Rate of Hauled-Out Harbor Seals ( Phoca vitulina ) during the Molt[END_REF] . The extent to which time in water, particularly during the molt, may affect thermoregulatory costs is poorly understood.

Southern elephant seals (SES) are one of only four species of phocids that undergo a 'catastrophic molt', during which they renew both their hair and cornified epidermis [START_REF] Perrin | Encyclopedia of Marine Mammals[END_REF][START_REF] Parsons | Read -2013[END_REF] . Of the four species, they are the only one to undergo the molt in a polar environment (other species: northern elephant seal (NES), Mirounga angustirostris [START_REF] Worthy | Moult energetics of the northern elephant seal (Mirounga angustirostris)[END_REF] , Hawaiian monk seal (Monachus schauinslandi) [START_REF] Atkinson | Reproductive morphology and status of female Hawaiian monk seals (Monachus schauinslandi) fatally injured by adult male seals[END_REF] , and Mediterranean monk seal (Monachus monachus) [START_REF] Badosa | Moult in the Mediterranean monk seal from Cap Blanc, western Sahara[END_REF] ). During this period, like other phocids, they lose a large proportion of their body mass (23% SES [START_REF] Slip | Body-Mass Loss, Utilization of Blubber and Fat, and Energetic Requirements of Male Southern Elephant Seals, Mirounga leonina, During the Molting Fast[END_REF] , 25%, NES [START_REF] Worthy | Moult energetics of the northern elephant seal (Mirounga angustirostris)[END_REF] , 17%, gray seals Halicheorus grypus [START_REF] Beck | Sex differences in the seasonal patterns of energy storage and expenditure in a phocid seal[END_REF] ). This large change, combined with the increased peripheral circulation which would result in high heat loss in water, led to the conclusion that elephant seals fast and remain on land during the molt [START_REF] Worthy | Moult energetics of the northern elephant seal (Mirounga angustirostris)[END_REF][START_REF] Boyd | Water Flux, Body Composition, and Metabolic Rate during Molt in Female Southern Elephant Seals (Mirounga leonina)[END_REF][START_REF] Carlini | Mass changes during their annual cycle in females of southern elephant seals at King George Island[END_REF][START_REF] Liwanag | Morphological and thermal properties of mammalian insulation: the evolution of fur for aquatic living[END_REF] . While ashore, they are exposed to a range of meteorological conditions. SES molt on subantarctic islands, they experience cold, wet, and windy conditions during the approximately one-month haulout [START_REF] Testut | The sea level at Port-aux-Français, Kerguelen Island, from 1949 to the present[END_REF] .

Environmental conditions strongly influence heat flux between an animal and the environment. SES minimize heat loss through social thermoregulation in large aggregations and through choice of different beach habitats such as grass or mud pools [START_REF] Chaise | Local weather and body condition influence habitat use and movements on land of molting female southern elephant seals (Mirounga leonina)[END_REF][START_REF] Chaise | Environmental and physiological determinants of huddling behavior of molting female southern elephant seals (Mirounga leonina)[END_REF] . Therefore, we would predict that only animals with sufficient energy reserves to cover the cost of fasting, molting, and cold-water contact would be able to go to sea during the molting period.

A high energetic cost during the molt increases the depletion of energy reserves in blubber, with possible fitness consequences, such as lower survival or reproductive success for seals [START_REF] Guinet | Effect of body size, body mass, and body condition on reproduction of female South African fur seals (Arctocephalus pusillus) in Namibia[END_REF][START_REF] Crocker | Maternal Traits and Reproductive Effort in Northern Elephant Seals[END_REF] . Climate in the Southern Ocean is rapidly changing, and environmental conditions are known to impact heat loss and molting phenology in phocids [START_REF] Walcott | Thermoregulatory costs in molting Antarctic Weddell seals: impacts of physiological and environmental conditions[END_REF][START_REF] Sato | Meteorological factors affecting the number of Weddell seals hauling-out on the ice during the molting season at Syowa Station, East Antarctica[END_REF] . In this context, understanding how energetic constraints and individual strategies may help reduce metabolic costs of animals during key stages of their lifecycle is important. While it is commonly agreed that molting SES remain on land and rely on their reserves, breaking the fast has already been suggested as a mechanism to mitigate physiological costs while molting by restoring blubber reserves or limiting metabolic water production [START_REF] Boyd | Water Flux, Body Composition, and Metabolic Rate during Molt in Female Southern Elephant Seals (Mirounga leonina)[END_REF] . However, few studies examined movement and potential drinking or feeding behavior in this species throughout the molt. One way to investigate at-sea feeding or dinking behavior is to combine stomach temperature measurements with time-depth recorders (TDRs). This allows detection of possible cold water or prey item ingestion through stomach temperature changes and to record the depth and location of ingestion events. This approach has previously been used in seabird research (penguins, cormorants, albatrosses [START_REF] Wilson | Can we determine when marine endotherms feed? A case study of seabirds[END_REF][START_REF] Charrassin | Feeding Behaviour of Free-Ranging Penguins Determined by Oesophageal Temperature[END_REF][START_REF] Pütz | Foraging Strategy of King Penguins (aptenodytes Patagonicus) During Summer at the Crozet Islands[END_REF][START_REF] Catry | Foraging strategies of grey-headed albatrosses Thalassarche chrysostoma: integration of movements, activity and feeding events[END_REF] , and captive or non-captive pinnipeds (NES and Californian sea lions [START_REF] Kuhn | Time to eat: measurements of feeding behaviour in a large marine predator, the northern elephant seal Mirounga angustirostris[END_REF][START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] ), but not during the molt.

In this study, we investigated the behavior of adult female SES during the molt. Females were instrumented with TDRs to document diving behavior and stomach temperature pills to document ingestion events. We hypothesized that female SES would remain on land, either in mud pools or on the beach, fasting, at least in the early stages of the molt to minimize heat loss. If seals did spend time at sea, we investigated if weather conditions influenced this behavior. Last we hypothesized that only females in good body condition would spend time at sea, as they have sufficient energy reserves to compensate for high heat loss.

Results

Combining diving analysis and stomach temperature recording, the monitoring duration was 7.0 ± 2.9 days of analyzed data (between 2 and 14 days of recording). Females arrived on land with a body mass of 314.7 ± 41.4 kg (BMI of 59.4 ± 5.1 kg/m 2 ). Molt stage when animals were equipped was 54 ± 25% with 41% of the females caught at the initial stage (n = 16), 41% at the mid stage (n = 16), and 18% at the final stage of molt (n = 7). Body mass at the end of the monitoring averaged 294.5 ± 37.7 kg, resulting in a daily body mass loss of 3.2 ± 1.4 kg per day. At this point all females were at the final stage of molt, with more than 90% of hair renewed. During the monitoring period, the mean daily wind speed was 8.8 ± 2.7 m/s (ranging from 2.8 to 18.4 m/s), mean daily air temperature was 8.4 ± 2.4 °C (ranging from 4.4 to 15.3 °C), mean daily total sunshine duration was 355.3 ± 219.9 minutes (ranging from 0 to 855 minutes) and mean daily relative humidity was 70.2 ± 7.7% (ranging from 50.7 to 91.6%).

Diving and surface swimming behavior

Between 2014 and 2022, 39 female elephant seals were captured and monitored and 79% went to sea (n = 31). A total of 660 dives were recorded, grouped in 77 dive cycles (Table 1), for 39% of the monitored females (n = 15). Mean dive duration was 7.7 ± 3.6 minutes, with a mean time to reach maximum depth of 3.2 ± 3.1 minutes, followed by a mean surface phase duration of 2.2 ± 2.5 minutes.

Dive cycles had an average duration of 1.4 ± 1.7 hours.

We detected a total of 375 surface swimming events with an average duration of 1.8 ± 2.6 hours grouped in 226 surface swimming cycles. Seventy-seven percent of monitored females (n = 30) performed surface swimming. Fourteen animals dived and surface swam. One female only dived.

On average, instrumented females spent time in the water (diving or surface swimming) every other day (% of monitored days with at-sea events = 49.2 ± 23.9%). The amount of time they spent in the water ranged from 9.0 to 92.8% of the day.

At-sea behavior was more diurnal, as 57% of the dives and 66% of the surface swimming occurred during the daytime. Excluding temperature drops during the ingestions, mean at-sea stomach temperature was higher than on land (at sea = 37.1 ± 0.3°C, on land = 36.5 ± 0.2°C, Student test, t = -7.3, df = 49.6, p-value < 0.0001). On land temperature analysis revealed hyperthermia events (from 1 to 3 events per individual) for 61.5% of the animals (n = 24), with a mean stomach temperature of 38.1 ± 0.3°C. In total, 33 hyperthermia events of 110 ± 39 min were analyzed, and the first at-sea event occurred within 24.5 ± 21.0 hours after.

A summary of ingestion event variables is available in Supplementary Table S1. We recorded a total of 87 ingestion events (Table 2), from 80% of individuals (n = 31 from total n = 39), with an average of 2.8 ± 2.1 ingestions per individual. Among these events, 70% occurred during the daytime.

A total of 10 ingestion events were detected during a dive (12%) and 42 events occurred during surface swimming (49%). Due to bad Argos locations, the remaining 37 events (39%) were not clearly characterized as at sea or on land, but were not associated with complete submersion of the animal according to wet and light sensors. These ingestion events could have happened strictly on land or in the tidal zone.

Results of the different methods from the literature [START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] are reported in Table 2 and based on the different methods, 25 to 53% of the ingestions were classed as potential prey ingestions. T 1 is the initial stomach temperature and T 2 the minimum temperature during the ingestion event.

Method

Threshold for feeding events

Number of feeding events

Index of rate of temperature recovery I (s.°C -1 ) I value>250 s.°C -1 n = 39 (44%)

Area above the curve (s.°C) Integral>3000 s.°C n = 25 (29%) Time of temperature recovery (Δt between T 2 -T 3 ) t rec >35 min n = 46 (53%)

Delta temperature T 1 -T 2 ΔT>4.7°C n = 22 (25%)
Determinants of female SES behavior At-sea behavior was not determined by initial physiological parameters; individual swimming score and the number of ingestions per female were influenced neither by BMI nor molt stage (Tables 3 and4).

Environmental conditions played a role in SES behavior. We found a positive effect of temperature and a negative effect of wind speed on the probability of surface swimming (Table 5).

Females tended to do more surface swimming during days of high temperature and days of low wind speed (Figures 1A and1B). The probability of diving was not related to meteorological conditions (Table 5).

We also found a positive effect of sunshine duration on the probability of ingestion. The probability of recording individuals that ingested increased during days with high total sunshine duration (Figure 1C).

The effect of relative humidity and wind speed on ingestion was not significant (Table 5). A: GLM predicted daily proportion of swimming females with daily mean wind speed (m/s). B: GLM predicted daily proportion of swimming females with daily mean temperature (°C). C: GLM predicted daily proportion of females that ingest with total daily sunshine duration (min/day).

Consequences on female SES condition

Female SES condition at the end of the molt was influenced by their behavior. For females going to sea, we found a positive relationship with the swimming score (PC1) and of the number of ingestions on daily body mass loss (Table 6). Females that dived and ingested more often were in better body condition at the end of the molt (Figures 2A and2B).

Discussion

Through the use of TDRs and STP, we identified surface swimming, diving, and ingestion events during the molt of female SES. To our knowledge, this study is the first to show evidence of SES breaking the fast during this energetically costly molt period.

We found no evidence of adverse effects of the STP on the behavior and body condition of animals at the end of the monitoring period. The STP assembly remains in the stomach, and the potential effect on satiety or ability to ingest was not possible to test. However, no such adverse effects have been described in experimental studies on pinnipeds [START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] , probably due to the short retention time and small size of the STP compared to the volume of the stomach.

Our data revealed that female SES went to sea during the molt, as reported in Table 1 and Figure S1. Indeed, nearly half of equipped individuals performed several dives, from 5 to 43 m.

To our knowledge, this behavior has not been reported yet in a species displaying a 'catastrophic' molt, including aquatic birds and mammals [START_REF] Beltran | Convergence of biannual moulting strategies across birds and mammals[END_REF] . In marine mammals, pinnipeds undergoing such an extreme physiological event, such as elephant seals [START_REF] Worthy | Moult energetics of the northern elephant seal (Mirounga angustirostris)[END_REF][START_REF] Boyd | Water Flux, Body Composition, and Metabolic Rate during Molt in Female Southern Elephant Seals (Mirounga leonina)[END_REF][START_REF] Carlini | Mass changes during their annual cycle in females of southern elephant seals at King George Island[END_REF][START_REF] Liwanag | Morphological and thermal properties of mammalian insulation: the evolution of fur for aquatic living[END_REF][START_REF] Carlini | Lactation costs in southern elephant seals at King George Island, South Shetland Islands[END_REF] , have always been thought to rely exclusively on energy reserves in blubber during the molt. All birds experiencing catastrophic molt are known to fast and avoid cold water contact, as demonstrated in cormorants [START_REF] Enstipp | The effects of depth, temperature and food ingestion on the foraging energetics of a diving endotherm, the double-crested cormorant (Phalacrocorax auritus)[END_REF] and penguins [START_REF] Adams | Energetics of Molt in Penguins[END_REF] . Few diving birds are known to break the fast and dive during the molting period, but they undergo a rapid simultaneous molt that is not reported as 'catastrophic' (common eider Somateria mollissima [START_REF] Guillemette | Flightlessness and the energetic cost of wing molt in a large sea duck[END_REF] , lesser snow geese Chen caerulescens caerulescens [START_REF] Ankney | Does the Wing Molt Cause Nutritional Stress in Lesser Snow Geese?[END_REF] , and grebes Podiceps sp. [START_REF] Stout | Timing and Location of Wing Molt in Horned, Red-necked and Western Grebes in North America[END_REF] ). Therefore, our results reveal that SES may be the first recorded case of a species experiencing a catastrophic molt while also spending time at sea, despite the potential energetic costs.

Although female SES dove during their molting fast, diving parameters differ from diving foraging parameters. Indeed, most of the dives were not deeper than 11.5 m and lasted on average for almost 7 minutes, compared to average foraging dive depth and durations of 400 m and 30 minutes [START_REF] Hindell | The Diving Behavior of Adult Male and Female Southern Elephant Seals, Mirounga leonina (Pinnipedia, Phocidae)[END_REF][START_REF] Mcconnell | Movements and foraging areas of naive, recently weaned southern elephant seal pups[END_REF][START_REF] Campagna | Post-Breeding Distribution and Diving Behavior of Adult Male Southern Elephant Seals from Patagonia[END_REF][START_REF] Mcintyre | A lifetime at depth: vertical distribution of southern elephant seals in the water column[END_REF] , respectively. SES are known to perform deeper dives according to prey distribution, migration, or predation avoidance [START_REF] Boeuf | Elephant seals: an introduction to the genus[END_REF][START_REF] Carlini | Food consumption estimates of southern elephant seal females during their post-breeding aquatic phase at King George Island[END_REF][START_REF] Baird | Factors influencing the diving behaviour of fish-eating killer whales: sex differences and diel and interannual variation in diving rates[END_REF] . Cold water exposure at shallow depths during this period thus requires further investigations to better understand the reasons for such behavior.

According to our data, female SES dive during the molt but also ingest water and/or food, which challenges the paradigm of fasting. Indeed, stomach temperature clearly shows that 80% of diving females ingest water and/or prey. Such behavior has already been suggested [START_REF] Boyd | Water Flux, Body Composition, and Metabolic Rate during Molt in Female Southern Elephant Seals (Mirounga leonina)[END_REF] as metabolic rate calculations based on water flux during the molting period indicate that water ingestion takes place, but no food was found in the stomachs of females. In our study, the type of ingestion (water and/or prey) remains unclear. Indeed, the results differ between the different methods of estimation, as supposed feeding events represent approximately 25 to 53% of ingestion events (Table 2), which is greater than previously described through behavioral and movement patterns [START_REF] Horsburgh | Determining feeding events and prey encounter rates in a southern elephant seal: a method using swim speed and stomach temperature[END_REF] .

It is difficult to distinguish between water or prey ingestion events in pinnipeds. While index I values (index of the rate of stomach temperature recovery, see Method section) of less than 30 s•°C -1 always denoted water ingestion for albatrosses [START_REF] Nadel | Energy exchanges in water[END_REF] , for pinnipeds, this distinction was more complicated [START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] . In a previous experimental study, index I values for prey ingestion ranged from 55.1 to 4380.0 s.°C -1 , while water ingestion ranged from 37.8 to 764.0 s.°C -1 . The previous study used a threshold of 250 s.°C -1 to distinguish fish from water consumption, as this value lowered the error rate of identification, but uncertainty remained [START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] . We used the same threshold in our study but as sea surface temperature was different (around 14°C in the experimental study [START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] , and 8°C in Kerguelen during the molting period [START_REF] Testut | The sea level at Port-aux-Français, Kerguelen Island, from 1949 to the present[END_REF] ), it may distort variable calculations and so ingestion type. In our study, as 49% of ingestion events occurred during surface swimming (i.e., depth between 0 to 5 m), and regarding prey repartition [START_REF] Carlini | Food consumption estimates of southern elephant seal females during their post-breeding aquatic phase at King George Island[END_REF] , half of ingestion events may likely involve water.

Across taxa, catastrophic molts in birds and mammals have always been associated with fasting [START_REF] Beltran | Convergence of biannual moulting strategies across birds and mammals[END_REF] . It appears that SES may be the first species reported to break the fast during this energetically costly period, but why?

In this study, we found that meteorological conditions influenced the behavior of molting female SES. The weather effect on social thermoregulation and habitat preference has already been described during the molt in this species [START_REF] Chaise | Local weather and body condition influence habitat use and movements on land of molting female southern elephant seals (Mirounga leonina)[END_REF][START_REF] Chaise | Implantation of subcutaneous heart rate data loggers in southern elephant seals (Mirounga leonina)[END_REF] . Meteorological conditions influence the behavior of molting pinnipeds, such as haulout frequency and time spent on land, but it has only been investigated in species of phocid seals that do not undergo a catastrophic molt and keep foraging at sea during this period [START_REF] Walcott | Thermoregulatory costs in molting Antarctic Weddell seals: impacts of physiological and environmental conditions[END_REF][START_REF] Sato | Meteorological factors affecting the number of Weddell seals hauling-out on the ice during the molting season at Syowa Station, East Antarctica[END_REF] .

Our data revealed that during days with low wind speed and days with high air temperature, female SES tend to swim more often. The same parameters were reported to influence the number of molting Weddell seals (Leptonychotes weddellii) hauling out on ice, but surprisingly, it was the opposite behavior, as Weddell seals tend to remain in the water when wind speed is elevated and air temperature are low [START_REF] Sato | Meteorological factors affecting the number of Weddell seals hauling-out on the ice during the molting season at Syowa Station, East Antarctica[END_REF] .

Meteorological conditions strongly differ between Kerguelen and Antarctica, where Weddell seals are Weddell seals and SES are not exposed to the same environmental conditions during their molting period, but both could lead to thermal discomfort. The thermoneutral zone (TNZ) is a range of temperature between a lower and upper threshold, between which the metabolic cost associated with thermoregulation is the lowest [START_REF] Kingma | The thermoneutral zone: implications for metabolic studies[END_REF] . Out of this range, animals are hypo-or hyperthermic, resulting in higher metabolic costs (thermogenesis) or heat dissipation (thermolysis) to avoid deleterious effects of overheating on the organism, such as water loss, cell-damage, and disruption of reproductive function [START_REF] Hansen | Effects of heat stress on mammalian reproduction[END_REF][START_REF] Alsharif | Comprehensive exploration of the molecular response, clinical signs, and histological aspects of heat stress in animals[END_REF] . Consequently, any supplementary energetic cost required for thermogenesis or thermolysis in both hypothermia or hyperthermia may increase energy depletion [START_REF] Guinet | Effect of body size, body mass, and body condition on reproduction of female South African fur seals (Arctocephalus pusillus) in Namibia[END_REF][START_REF] Crocker | Maternal Traits and Reproductive Effort in Northern Elephant Seals[END_REF] . Moreover, as phocid seals obtain their water requirements from the metabolism of fat reserves [START_REF] Ortiz | Water and Energy Flux in Elephant Seal Pups Fasting under Natural Conditions[END_REF][START_REF] Costa | The energetics of lactation in the Northern elephant seal, Mirounga angustirostris[END_REF] , compensating for metabolic water loss triggered by heat stress could be extremely costly. Going to sea could be a way to avoid extreme weather events when seals are out with their TNZ, leading to thermal discomfort and to other physiological effects. As SES remain in a warmer environment, they should avoid overheating and minimize elevated metabolism and increased water loss on warmer days, while Weddell seals, exposed to colder conditions, would go to sea to reduce metabolic costs of thermogenesis in bad weather conditions.

We were not able to obtain solar radiation in W/m 2 , but instead used sunshine duration (minute per day), which is a less precise estimate of the thermal power received at the surface of the skin. The effect of sunshine duration was not significant in initiating at-sea movements in our females, but solar radiation was already reported to be positively correlated with swimming behavior during the breeding period of females NES [START_REF] Codde | Effects of environmental variables on surface temperature of breeding adult female northern elephant seals, Mirounga angustirostris, and pups[END_REF] and other pinnipeds [START_REF] Campagna | Thermoregulatory behaviour of southern sea lions and its effect on mating strategies[END_REF][START_REF] Twiss | Behavioral evidence of thermal stress from overheating in UK breeding gray seals[END_REF] . Heat dissipation is maximized by peripheral vasodilatation and by an important thermal gradient through thermal windows (surface temperature-air temperature [START_REF] Mauck | Thermal windows on the trunk of hauled-out seals: hot spots for thermoregulatory evaporation[END_REF] ). If peripheral circulation is already increased during the molt, and solar radiation heats blood at the skin surface, heat loss by radiation or convection may not be sufficient to cool down and prevent thermal stress during warm days. Because of the high cooling capacity of water, going to sea would be the most efficient method to dissipate heat [START_REF] Campagna | Thermoregulatory behaviour of southern sea lions and its effect on mating strategies[END_REF] . This suggests that SES could be subject to thermal stress and go into the water to avoid overheating, especially during the molt when vasodilatation at the skin surface occurs.

Total sunshine duration was correlated with the number of ingestion events in our females. As ingestion events were rare during a dive (12% of ingestion events), this would be more consistent with drinking than foraging. Drinking at sea has already been reported in gray seals [START_REF] Twiss | Behavioral evidence of thermal stress from overheating in UK breeding gray seals[END_REF] and would be in line with a behavioral response to thermal stress to avoid supplementary metabolic costs and blubber depletion needed to restore hydration if they remain on land.

Although the majority of our results confirm a behavioral response to thermal stress, few hyperthermia events were detected (from 1 to 3 events for 61.5% of the animals) and were not related to an immediate at-sea event (first at sea event within 24.5 ± 21.0 hours after a detected hyperthermia). In breeding NES, a strong effect of solar radiation on surface temperature was reported and was related to at sea movement [START_REF] Codde | Effects of environmental variables on surface temperature of breeding adult female northern elephant seals, Mirounga angustirostris, and pups[END_REF] . As heat is gained by radiation, an increase in surface temperature may be most relevant to hyperthermia events. Considering the blubber thickness in phocid seals [START_REF] Ryg | Estimating the Blubber Content of Phocid Seals[END_REF][START_REF] Slip | Determining Blubber Mass in the Southern Elephant Seal, Mirounga leonina, by Ultrasonic and Isotopic Techniques[END_REF][START_REF] Mellish | Beneath the surface: Profiling blubber depth in pinnipeds with infrared imaging[END_REF] , behavioral responses to high surface temperature (i.e. going to sea) may occur rapidly after an increase in surface temperature, probably before stomach temperature increased through heat diffusion by conduction.

This may question the relevance of using stomach temperature for detecting overheating in response to environmental factors in this species.

Finally, our data did not show any link between at-sea movements and stage of molt, where we expected more at sea movements when heat loss is reduced at the end of the molt [START_REF] Walcott | Thermoregulatory costs in molting Antarctic Weddell seals: impacts of physiological and environmental conditions[END_REF] . This may indicate that heat loss and the metabolic cost of cold-water immersion are not limiting factors for this behavior, in line with possible thermal stress events and the need for heat dissipation rather than conservation.

Considering high energetic constraints triggered by cold water contact and previous studies reporting that body condition could influence molting duration [START_REF] De Kock | Determinants of moult haulout phenology and duration in southern elephant seals[END_REF] , we thought female SES with a high BMI would be less constrained by energetic trade-off and spend more time at sea than females in lower body condition. However, our data did not find any evidence that body condition influenced the behavior of molting females, neither at-sea movements nor ingestion events. Molt stage also did not influence female behavior despite less energetic constraints at the end of the molt [START_REF] Walcott | Thermoregulatory costs in molting Antarctic Weddell seals: impacts of physiological and environmental conditions[END_REF] , which suggests an environmental rather than a physiological driver of this behavior.

Moreover, going to sea during the molt might not be as costly as we believed. Daily specific body mass loss of our females was a good indicator of energetic loss during the molt. A previous study reported that the mass loss of female elephant seals averages 4.7 kg/d, during 25 to 30 days of molting [START_REF] Boyd | Water Flux, Body Composition, and Metabolic Rate during Molt in Female Southern Elephant Seals (Mirounga leonina)[END_REF] . Surprisingly, females that went to sea did not lose more body mass than females remaining on land but had higher stomach temperatures, which could reflect a higher metabolic rate, hence higher energy loss at sea.

However, previous studies on molting Arctic seals (ringed Pusa hispida, spotted Phoca largha, and bearded seals Erignathus barbatus) reported that metabolic rates were similar when resting in air and water [START_REF] Thometz | Maintaining control: metabolism of molting Arctic seals in water and when hauled out[END_REF] . An increase in stomach temperature might be detected at the onset of diving as a result of heat generated by muscles during swimming [START_REF] Wilson | Reliability of Stomach Temperature Changes in Determining Feeding Characteristics of Seabirds[END_REF] , which questions the reliability of STP to estimate metabolic variation.

According to our results, females may benefit from trips to sea. Among the females that went to sea, the more they dived and ingested, the less mass they lost. The diving profile of these females was very similar to foraging diving profiles, suggesting they could ingest prey items during their trip. Although depth and duration are very different from typical foraging dives, high shallow biomass sites related to phytoplankton bloom have been located in the vicinity of the Kerguelen Plateau during spring and summer, with a peak between December-February [START_REF] Rembauville | Plankton Assemblage Estimated with BGC-Argo Floats in the Southern Ocean: Implications for Seasonal Successions and Particle Export[END_REF] . Many studies have shown that juvenile SES perform shallower dives during their first year at sea and that their diet is mainly composed of krill (Euphausia sp.) [START_REF] Lubcker | Low trophic level diet of juvenile southern elephant seals Mirounga leonina from Marion Island : a stable isotope investigation using vibrissal regrowths[END_REF][START_REF] Orgeret | Body condition influences ontogeny of foraging behavior in juvenile southern elephant seals[END_REF][START_REF] Walters | Spatially Explicit Estimates of Prey Consumption Reveal a New Krill Predator in the Southern Ocean[END_REF] . As molting females are constrained to stay close to the island until the end of the molting process, they could be limited by the bathymetry and benefit from shallower prey such as krill, which could restore body reserves if the molting period is too long or too costly to rely on body fat. As these are very small prey items, that could also explain the difficulty of distinguishing between water and prey items from ingestion curves. However, no precise information on what was ingested could be determined with this method, and thus this question requires further investigation. Other methods such as sonar tag or video camera [START_REF] Lawson | Development of an animal-borne "sonar tag" for quantifying prey availability: test deployments on northern elephant seals[END_REF][START_REF] Goulet | A miniature biomimetic sonar and movement tag to study the biotic environment and predator-prey interactions in aquatic animals[END_REF][START_REF] Adachi | Forced into an ecological corner: Round-the-clock deep foraging on small prey by elephant seals[END_REF] could collect further important information which would determine precisely what is ingested during these trips to sea during the molt Energetic constraints and metabolic costs associated with molting behavior, as well as the possible fitness consequences, still remain unclear.

Whether seals remain on land to limit heat loss and metabolic costs from unavoidable perfusion during the molt or whether this behavior allows a faster molt remains uncertain. Avoiding cold water would limit energy expenditure and blubber depletion, while a faster molt would limit fasting duration and extend the next foraging period [START_REF] De Kock | Determinants of moult haulout phenology and duration in southern elephant seals[END_REF] , resulting in higher at-sea body condition, survival, and reproductive success [START_REF] Guinet | Effect of body size, body mass, and body condition on reproduction of female South African fur seals (Arctocephalus pusillus) in Namibia[END_REF][START_REF] Crocker | Maternal Traits and Reproductive Effort in Northern Elephant Seals[END_REF] . Previous studies on ringed and spotted seals did not report supplementary energy expenditure at sea [START_REF] Thometz | Maintaining control: metabolism of molting Arctic seals in water and when hauled out[END_REF] , and our data did not show any difference in body mass loss between at-sea and onland females. This highlights that the physiological cost of molting, i.e., for tissue regeneration, may be greater than the cost of heat loss in cold water. Spending an extended time at sea would be costly by slowing down the molt. Unfortunately, because the molting stage is difficult to determine and to assess without regular visual checks, we were not able to investigate to what extent the amount of time spent at sea influenced the duration of the molting period. This would be of strong interest as this equilibrium of haul out frequency and molt duration may be compromised by current global changes and rapid warming at the poles [START_REF] Gille | Warming of the Southern Ocean Since the 1950s[END_REF] . Thermal stress could affect the behavior of seals, increasing molt duration and causing a greater depletion of blubber reserves. In this context, knowing how molt duration impacted ingestion behavior in females is of interest. Seals with a slower molt may need to restore their body reserves to make sure they end the molting process with sufficient body condition to ensure good foraging success and survival during their next post-molt foraging trip. Thus, the link between energetic constraints, molting phenology, and behavior of SES on land needs further investigation.

This study found that female SES travel at sea during the molt, performing shallow and short dives or surface swimming, and these behaviors were associated with ingestion events. This shows that, SES frequently break the fast and may not always remain on land relying exclusively on blubber reserves.

While environmental factors responsible for heat stress were determinants of swimming behavior and likely water ingestion, physiological and fitness consequences of diving and ingestion events need to be further investigated. This will allow a better understanding of the energetic constraints that drive this critical period and the extent to which thermal stress may impact SES. Considering rapid changes in polar climates and possible fitness consequences, the effect of warmer conditions is of particular interest for the conservation of polar phocids.

Methods

Data collection and analysis

All scientific procedures were approved by the Ethics Committee of the French Polar Institute.

Data were collected during the austral summer molt (December-February) between 2014 and 2022. The field work took place at three colonies within the Kerguelen Archipelago: Pointe Suzanne (49°26'S, 70°26'E) between 2014 and 2019, Estacade (49°16'S, 70°32'E) in 2020 and 2022, and Port-Aux-Français (49°34'S, 70°21'E) in 2021.

Female elephant seals were captured during the molt and anesthetized using tiletamine and zolazepam (Zoletil® 100 [START_REF] Chaise | Implantation of subcutaneous heart rate data loggers in southern elephant seals (Mirounga leonina)[END_REF][START_REF] Mcmahon | Field immobilisation of southern elephant seals with intravenous tiletamine and zolazepam[END_REF] ). Individuals were equipped with devices provided by Wildlife Computers Argos location was obtained each day from resulting transmissions. Locations are classified as 3, 2, 1, 0 according to the error radius (<250m, 250-500m, 500-1500m, >1500m). We show an example of good atsea locations in Supplementary Figure S1. Stomach temperature pills (STP) were placed in the stomach under anesthesia using a lubricated flexible tube, and SPLASH10/TDR10 tags were glued on the head with epoxy bi-component glue (Araldite®). Data-logging tags were set to measure depth (resolution of 0.5 m with an accuracy of 1% of reading), light-level (range from 5 x 10 -12 W/cm² to 5 x 10 2 W/cm² with a resolution of 20 units/decade), stomach temperature (resolution: ± 0.1°C; accuracy: ± 0.3°C), and wet/dry sensor every 10 s. Tags were retrieved at recapture, while remaining STP were naturally ejected later at sea or on land. Individuals were recaptured between the completion of the molt and their final departure to sea.

Of the 55 instrumented seals, we obtained stomach temperature data over 2 days from 39 of the seals. Data were analyzed starting from 6 hours following capture (to discard the effects of anesthesia) until the STP was ejected or the seal was recaptured. For each individual, the molting stage was visually estimated at both capture and recapture and during daily monitoring (0-40%: initial stage; 50-80%: mid stage; >90%: final stage, as described in previous study [START_REF] Chaise | Local weather and body condition influence habitat use and movements on land of molting female southern elephant seals (Mirounga leonina)[END_REF] ). Eighteen of the instrumented seals were weighed at capture and recapture, allowing us to calculate the daily mass loss (kg/day). Length (m) was calculated from the mean length measured at capture and recapture. From this, we calculated a body mass index (BMI, kg/m 2 ).

Local meteorological data was retrieved from Météo-France base station archives in Port-aux-Français (Kerguelen archipelago). These data included temperature under cover (°C), relative humidity (%), sunshine duration (min), and wind speed (m/s). Data were recorded per hour and summed per day for sunshine duration.

Data were processed and analyzed using "pandas", a Python data analysis package (versions: Python 3.10; pandas 1.5.0), and R software (R version 4.1.2).

Diving pattern analysis

Because Argos locations were poor, diving patterns were analyzed only from depth, light level, and wet/dry sensor data. When necessary, a depth-zero correction was made on land at the time of capture. Diving behavior was determined using a Python algorithm especially developed for this study (Hex•Data, France). To make sure light level variations involved depth and not daily changes, day-night light-level variations were removed using a seasonal decomposition function based on moving averages (function "seasonal decompose" from Python package "statsmodels"; version 0.13.2). We combined a depth threshold of 0.5 m and a "wet" display to spot the start of a dive. To distinguish mud pools (wallows) from sea-water baths, we made sure the light level varied by more than 5 units (values ranging from 0 to 255) during the presumed dive.

At-sea behavior was characterized by 1) a submerged phase, 2) a maximum depth, and 3) a surface phase. We distinguished surface swimming and diving behavior according to maximum depth.

Surface swimming was defined to occur between 1 and 5 m, with a maximum surface time of 20 minutes between two submerged phases (based on our own data exploration, Figure 3A). Dives were described by a descent, a bottom, and an ascent phase with a maximum depth greater than 5 m and showed different profiles (Figures 3B, 3C, 3D). A dive cycle was characterized by at least two successive dives separated by less than 20 minutes at the surface, as surface duration intervals showed a break around 17 minutes. Events were described by their mean duration, mean and maximum depth, and frequency. Stomach temperature analysis Ingestion events were identified by a sharp decline in stomach temperature followed by a logarithmic increase (Figure 4A, 4B, 4C, 4D). The ingestion detection algorithm identified:

1. The minimum temperature below 36.5°C (under the lowest core temperature described for elephant seals [START_REF] Chaise | Environmental and physiological determinants of huddling behavior of molting female southern elephant seals (Mirounga leonina)[END_REF][START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] ), referred to as T 2

2. The previous stable temperature before the drop (T 1 , backward from T 2 )

3. The point at which temperature returned to baseline for at least 10 minutes [START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF][START_REF] Sauvé | Stomach Temperature Records Reveal Nursing Behaviour and Transition to Solid Food Consumption in an Unweaned Mammal, the Harbour Seal Pup (Phoca vitulina)[END_REF] (T 3 , forward from T 2 )

T 1 , T 2 and T 3 are illustrated in Figure 4A. Events that were close together were merged into a single event.

Each ingestion event was assigned to a female behavior: on land, diving, surface swimming, or unknown.

Following the algorithm analysis, a visual check of ingestion curves led to the removal of 12 anomalous events (non-logarithmic curves or abrupt variations consistent with STP measurement errors). The STP was considered lost when the stomach temperature reading remained constant for at least 3 hours.

Outliers were deleted using a filter based on the rolling average and bounded by the 1 st and 3 rd quartiles.

To examine STP temperature drift over time, we downsampled the data to one measurement every 15 minutes (factor of 100) and examined the trend in temperature over time using Kendall's tau correlation coefficient. The temperature increased for 16 individuals, decreased for 12 individuals, and did not change for the remaining 11 individuals. The mean absolute value of the correlation coefficient was τ = 0.11 ± 0.09, with the mean absolute value of the slope estimator s = 5.1.10 -7 ± 6.2.10 -7 , corresponding to a variation of ± 0.1°C every 10 days (for 72% of the 39 individuals; n = 31). Therefore, based on the temperature pill accuracy (± 0.3°C) and mean survey duration (over a week), we considered that the signal drift was trivial and chose not to apply a correction.

STP were synchronized with diving patterns, that were filtered with a seasonal decomposition of light-level function to cancel the effect of the day/night cycle. As this function required 48 hours to work, six animals with less than 2 days of recording were discarded (R documentation). Eight seals ejected the pill before recapture. In total, 80% of monitored seals were recaptured with the temperature pill still recording (n = 31), with an average retention duration of 7.2 ± 2.9 days.

To distinguish between water and prey ingestions, we followed two published methods [START_REF] Catry | Foraging strategies of grey-headed albatrosses Thalassarche chrysostoma: integration of movements, activity and feeding events[END_REF][START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] , using the index of the rate of stomach temperature recovery (I, s.°C -1 ), calculated as follow:

I = t 0.5 / (T 1 -T 2 )
where T 1 (°C) is the initial stomach temperature before the drop due to the ingestion of sea water, T 2 (°C)

is the minimum temperature reached during the drinking or feeding event, and t 0.5 (seconds) is the time from the beginning of the temperature decrease to the point of half recovery (half-way temperature between initial T 1 and minimum T 2 ; Figure 4A). The threshold of 250 s.°C -1 was used to distinguish between fish and water consumption, as previously reported [START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF] .

We also calculated the area above the curve (integral) of drop in stomach temperature during ingestion events, as it may be related to ingested mass in NES, based on the trapezoid method [START_REF] Kuhn | Identifying and quantifying prey consumption using stomach temperature change in pinnipeds[END_REF][START_REF] Wilson | Reliability of Stomach Temperature Changes in Determining Feeding Characteristics of Seabirds[END_REF] (for more details, see Supplementary Figure S2).

Ingestion events were compiled with dry/wet and light sensor to identify whether they occurred at sea or on land (mud pools).

We investigated on-land stomach temperatures to detect hyperthermia events that could have initiated at sea movements. We calculated the mean stomach temperature on land (36.6 ± 0.2°C) and considered hyperthermia if values were higher than the 97.5% quantile for more than one hour. To investigate the reason for variability in SES swimming score, we used linear mixed models (LMM) with molting stage when equipped, BMI, monitoring duration as explanatory variables, PC1 (group diving) or PC2 (group surface swimming) as response variables. To determine if physiological parameters influenced ingestion behavior, we ran a generalized linear mixed model with molting stage when instrumented, BMI, monitoring duration as explanatory variables, ingestion counts per individual as response variable. To correct for overdispersion, we used a negative binomial distribution [START_REF] Payne | An empirical approach to determine a threshold for assessing overdispersion in Poisson and negative binomial models for count data[END_REF] . Each time, animal ID was used as random. For each model, an ANOVA type II was performed (Anova function in R library 'car').

Then, to determine if weather influenced when seals spent time in the water we ran a generalized linear model with temperature, relative humidity, sunshine duration and wind speed as explanatory variables, and the daily probability of female SES diving, surface swimming, and ingesting as response variables.

Models were fitted with a binomial distribution (logistic regressions for probabilities), checked for overdispersion, and adjusted with a quasibinomial distribution if necessary.

Last, to determine if changes in SES behavior and molt phenology influenced their condition before their next travel, we used LMM with the swimming score, ingestion counts, body mass/length and molting stage at capture, and monitoring duration as explanatory variables, body mass loss (kg) as response variable, and animal ID as random.

Figure 1 :

 1 Figure 1: Relationships between meteorological conditions and behavior of female southern elephant seals using.

Figure 2 :

 2 Figure 2: Daily mass loss per unit of body mass (g/kg/day) of female southern elephant seals according to their behavior. A. Diving score (PC1 as individual values on the first component of the PCA) and B. Number of ingestions per individual. Individuals with high PC1 values perform more dives, that last longer, and show more surface swimming.

(

  USA): TDRs (TDR10-LX-340, 57 x 38 x 30 mm, 75 g in air), Argos satellite transmitters (SPLASH10-L-309D, 76 x 55 x 32 mm, 125 g in air) and Stomach Temperature Pills (TDR-STP-207D, 63 x 21 mm, 31 g in air).

Figure 3 :

 3 Figure 3: Diving parameters during different at-sea behaviors; diving or surface swimming. Surface swimming occurs between 1 and 5 m, while a dive is characterized by a maximum depth of more than 5 m. A dive or a surface swimming cycle is characterized by at least two successive dives or surface swimming separated by less than 20 min at the surface. Fig 3A. represents a surface swimming cycle and different profiles of dive cycles (B, C, D) of a female southern elephant seal in 2017. Each dive is defined by the succession of a submerged phase (blue area) and a surface phase (green area) (B).

Figure 4 :

 4 Figure 4: Stomach temperature variations (°C) during ingestion events recorded for two female Southern elephant seals in 2014 and 2019.A: standard temperature variation. B, C: double ingestions. D: extreme temperature variations T 1 is the initial temperature, T 2 the minimum temperature, T 3 the recovery temperature, ΔT the difference of temperature between T 1 and T 2 , T 0.5 the half-way recovery temperature between T 1 and T 2 (T 0.5 = T 2 + ΔT/2) and t 0.5 the time of half-way recovery (black arrow: t 0.5 = t T0.5 -t T1 ). The area above the curve (integral) was calculated from the asymptote.

Figure 5 :

 5 Figure 5: Principal Component Analysis (PCA) including number of dives per individual, number of surface swims per individual, and mean dive or surface swimming duration. The first component (PC1) accounted for 59.0% of the variation and the second component (PC2) accounted for 23.8% of the variation. PC1 was characterized by number of dives, number of surface swims, and mean dive duration. PC2 was defined by surface swimming duration. Individuals are reported on the PCA and identified through their behavior (red circles, diving; orange star, on land; blue triangle, surface swimming only). Orange star represents eight individuals on the same point.

Table 1 : Summary of diving parameters from 31 female southern elephant seals during the molt

 1

	Among 31 female who went at sea, 15 dived (n = 660 dives, 77 dive cycles and 226 episodes of surface
	swimming; 2014-2022). 'At-sea events' include both surface swimming and diving.
		Mean (SD)	Min -Max
	Estimated time spent at sea per day per	109.32 (98.3)	1.0 -391.0
	individual (min)
	Mean number of at-sea events per day per	1.1 (0.8)	0.1 -2.8
	individual
	Total number of dive cycles per individual	5.1 (5.5)	1 -22
	Total number of dives per dive cycle	8.6 (10.8)	1 -49
	Total number of dives per individual	44.0 (55.0)	1 -157
	Maximum dive depth (m)	12.5 (7.3)	5 -43
	Dive duration (min)	7.7 (3.6)	0.2 -22.5
	Time at surface (min)	2.2 (2.5)	0.3 -19.3
	Surface swimming duration (h)	1.8 (2.6)	0.2 -26.7

Table 2 : summary of ingestion type based on Kuhn and Costa (2006) results, from 31 female southern elephant seals monitored between 2014 and 2022 (n = 87 events).

 2

Table 3 . Best models to explain female southern elephant seals swimming score variability

 3

	Response	Behavior /	Explanatory	X 2	Df	P	AICc
	variable	group	variables
	PC1	Diving	Monitoring	13.43 1	< 0.001 ***	63.3
			duration
	PC2	Surface	Monitoring	0.34	1	0.56	56.5
		swimming	duration
	Response variable	Location	Explanatory variables Coefficient ±	Z	P
							SE
			At-sea		Intercept		0.54 ± 0.43	0.95	0.20
	Number of			Monitoring duration	0.03 ± 0.05	1.07	0.51
	ingestions		On land		Intercept		-1.95 ± 2.95 -0.66	0.51
				Monitoring duration	0.29 ± 0.48	0.60	0.55

ANOVA table of the best linear mixed effect models for at-sea behavior (PC1 and PC2): diving (n=15) or surface swimming (n=31). *** : p-value < 0.001

Table 4. Best models to explain female southern elephant seals ingestion behavior variability

Summary of coefficients and goodness-of-fit indices from the best models for the number of ingestions (generalized linear models fitted with negative binomial law), at-sea (n=32) or on land (n=7).

Table 5 . Summary of coefficients and goodness-of-fit indices from the best models for environmental conditions effect on female southern elephant seals behavior

 5

	Response variable	Explanatory variables	Coefficient ± SE	t	P
		Intercept	-1.7 ± 0.8	-2.0	0.04 *
	Daily proportion of	Temperature	0.06 ± 0.08	0.8	0.44
	diving females	Wind speed	-0.09 ± 0.06	-1.4	0.16
	Daily proportion of	Intercept	-1.6 ± 0.6	-2.7	0.008 **
	surface swimming	Temperature	0.21 ± 0.06	3.7	<0.001 ***

Generalized linear models were fitted with binomial (probability of ingesting) or quasibinomial (probability of diving and surface swimming) law. Females behavior is separated as diving behavior (n=15 females), swimming behavior (n=31 females), ingesting behavior (n=31 females). * : p-value < 0.05; ** : p-value < 0.01; *** : p-value < 0.001

Table 6 . ANOVA table of the best linear mixed effect models for female southern elephant seals condition at the end of the molting period.

 6 Body mass loss is used as a proxy for female southern elephant seals condition. Females are grouped by location: on land (n=6) or at sea (n=12).

	Response variable	Location	AICc	Explanatory variables	X 2	Df	P
				Mass start	0.38	1	0.53
		On land	46.9	Length	0.27	1	0.61
				Monitoring duration	1.41	1	0.24
	Body mass loss			Mass start	0.02	1	0.89
				Length	0.37	1	0.54
		At-sea	126.7	PC1	8.19	1	0.004 **
				Number of ingestions	4.42	1	0.03 *
				Monitoring duration	10.65	1	0.001 **

* : p-value < 0.05; ** : p-value < 0.01

  found. If daily wind speed is nearly equal (8.8 ± 2.7 m/s, ranging from 2.8 to 18.4 m/s in Kerguelen and 5.3 ± 4.2 m/s, ranging from 0.7 to 19.8 m/s in Syowa station), air temperature does not go below 0°C during the molting period in Kerguelen (8.4 ± 2.4 °C, 4.4 to 15.3 °C versus -8.3 ± 5.3 °C, with a maximum of 1.7 °C in Syowa).

Acknowledgements

The overall study was funded by the Institut Polaire Français Paul-Emile Victor (IPEV Programs 1037 HEnergES and 1201 Cycleleph) and doctoral fellowships of French Ministry of Higher Education and Research. We thank the Terres Australes et Antarctiques Françaises for logistic support, and the fieldwork volunteers who helped in tags deployments and retrievals (in alphabetic order; Hassen Allegue, Jérôme Badaut, Batshéva Bonnet, Antoine Bertault, Laureline Chaise, Laura Charlanne, Océane Cossu-Doye, Lucas Delalande, Liane Dupon, Susan Gallon, Manon Ghislain, Christophe Guinet, Adélie Krellenstein, Alex Lathuilliere, Marion Nebot, William Paterson, Julie Pauwels, Baptiste Picard, Erwan Piot, Manon Potin, Camille Toscani, Martin Tournier, Yakov Uzan, Coline Vulliet, Pauline Vuarin). D.M was funded by the Carnegie Trust for the Universities of Scotland.

Data availability

All diving data are available in the figshare public data at: 10.6084/m9.figshare.24773235

Code availability

The Python code is available on request from the authors.

The R code can be downloaded from Zenodo 85 .

Author contributions

C.G. and A.A. and D.M conceived and designed the overall study. L. Chaise, L. Charlanne and E. P. contributed to field work. L. Chaise and D.S. conceived the algorithm and performed the analyzes. L.

Charlanne performed the statistical analyzes and wrote the manuscript. All authors reviewed and agreed on the final content of the manuscript.

Competing interests

The authors declare no competing interests.

Supplementary information

Breaking the fast: First report of dives and ingestions events in moulting southern elephant seals. We used the equation:

Laura Charlanne

Area event = |area trapezoid | -(|T 3 -T 1 | * (t 3 -t 1 )) / 2

Where area trapezoid was calculated using the integral function "trapezoid()" from Python package "scipy" (version: 1.9.1), and T 1 , T 3 (°C) and t 1 , t 3 (s) are respectively the stomach temperature and time at points T 1 and T 3 (start and end of the ingestion event).

Recovery temperature T 3 can be greater than initial temperature T 1 (A) or lower (B) (based on Kuhn and Costa, 2006): the grey area below corresponds to area trapezoid calculated with the trapezoid method, and hatched area corresponds to half of the additional rectangular area calculated (|T 3 -T 1 | * (t 3 -t 1 ) / 2). S1: Summary of ingestion event variables from 31 female Southern elephant seals monitored between 2014 and 2022 (n = 87 events).

Supplementary Table

Mean (SD)

Min -Max Minimum temperature T 2 (°C)