Nelly Ménard
email: nelly.menard@univ-rennes1.fr

Peggy Motsch

Alexia Delahaye

Alice Saintvanne

Guillaume Le Flohic

Sandrine Dupé

Dominique Vallet

Mohamed Qarro

Mohamed Ibn Tattou

Jean-Sébastien Pierre

Ecobio

Effect of habitat quality on diet flexibility in Barbary macaques

Keywords: Macaca sylvanus, diet, habitat quality, grazing pressure, temperate forests

Barbary macaques live in extreme temperate environments characterized by strongly seasonal resource availability. They are mainly terrestrial while foraging, harvesting food from the herbaceous layer. These monkeys are threatened mainly because of anthropogenic habitat degradation. We studied the adaptive capacities of wild groups of Barbary macaques that lived in different cedar forests undergoing varying extents of grazing pressure from domestic livestock. In all three sites, diet varied seasonally. Heavy grazing led to a significant decrease in herbaceous production and species richness. As a consequence, the monkeys' diet in this poor habitat showed a decreased plant species richness. Moreover, it incorporated fewer above-ground herbaceous resources, and a greater proportion of subterranean resources (especially hypogeous fungi and subterranean invertebrates such as earthworms, eggs and adults of earwigs, and ant's larvae) than the diet of monkeys inhabiting ungrazed forest. Cedar bark, cedar strobiles, earthworms and earwigs were part of the monkeys' diet only in grazed forest. Monkeys in heavily grazed forest compensated for a lack of herbaceous foods by eating subterranean foods preferentially to tree and shrub products. The foods they consumed take longer to harvest and process than the seeds or leaves consumed by Barbary macaques in less heavily grazed forest habitats. Our results suggest that monkeys do differ in their diets according to the degree of habitat change induced by human activities. They also highlight the dietary flexibility of Barbary macaques as a key element that allows them to cope with degraded habitats. We later compare the dietary adjustments of Barbary macaques facing environmental change to dietary strategies of other macaques and temperate-zone primates.

INTRODUCTION

The expansion of human population results in spatial overlap between domestic livestock and wild animals, and competition will occur if they have to share food resources [START_REF] Odadi | African wild ungulates compete with or facilitate cattle depending on season[END_REF]. Intense pastoralism may also lead to decreased habitat quality, which may endanger wild populations of herbivores [START_REF] Bagchi | Conflicts between traditional pastoralism and conservation of Himalayan ibex (Capra sibirica) in the Trans-Himalayan mountains[END_REF][START_REF] Bhattacharya | Natural resource use by humans and response of wild ungulates[END_REF][START_REF] Sitters | Herded cattle and wild grazers partition water but share forage resources during dry years in East African savannas[END_REF]. Generalist herbivores are more prone to persist in degraded habitats thanks to the great flexibility in their choice of food resources.

Acquiring food energy in conditions of food restriction (poor habitats or seasonal food shortage) involves the ability to change diet composition [START_REF] Charnov | Optimal foraging -attack strategy of a mantid[END_REF][START_REF] Fiore | Time allocation patterns of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in a neotropical terra firma forest[END_REF][START_REF] Emlen | Role of time and energy in food preference[END_REF][START_REF] Ménard Macarthur | On optimal use of a patchy environment[END_REF][START_REF] Schoener | Theory of feeding strategies[END_REF][START_REF] Vasey | Activity budgets and activity rhythms in red ruffed lemurs (Varecia rubra) on the Masoala Peninsula, Madagascar: seasonality and reproductive energetics[END_REF].

Studies on non-human primates have shown that they may respond to a reduction in food availability by incorporating scarce but high-return foods or by optimizing their food intake on abundant but low-quality food [START_REF] Hill | Day length, latitude and behavioural (in)flexibility in baboons (Papio cynocephalus ursinus)[END_REF][START_REF] Sayers | Himalayan Semnopithecus entellus at Langtang National Park, Nepal: diet, activity patterns, and resources[END_REF][START_REF] Tsuji | Feeding strategies of primates in temperate and alpine forests: comparison of Asian macaques and colobines[END_REF][START_REF] Van Doorn | The effects of extreme seasonality of climate and day length on the activity budget and diet of semi-commensal chacma baboons (Papio ursinus) in the Cape Peninsula of South Africa[END_REF]Wrangham et al., 1998]. The strategy they adopt may lead them to a diet including low profitability (e.g. energy/handling time) items (like Himalayan gray langurs, Semnopithecus entellus, in winter [START_REF] Sayers | Optimal foraging on the roof of the world: Himalayan langurs and the classical prey model[END_REF]).

Most species of primates exhibit some degree of diet flexibility that allows them to cope with seasonality of resource availability or with inter-site differences of habitat quality due to altitude, latitude, habitat fragmentation/loss, or habitat degradation [START_REF] Campbell-Smith | Raiders of the lost bark: orangutan foraging strategies in a degraded landscape[END_REF][START_REF] Chaves | Dietary flexibility of the brown howler monkey throughout its geographic distribution[END_REF][START_REF] Chaves | Differences in diet between Spider monkey groups living in forest fragments and continuous forest in Mexico[END_REF][START_REF] Naughton-Treves | Temporal patterns of cropraiding by primates: linking food availability in croplands and adjacent forest[END_REF][START_REF] Quéméré | A DNA metabarcoding study of a primate dietary diversity and plasticity across its entire fragmented range[END_REF][START_REF] Riley | Flexibility in diet and activity patterns of Macaca tonkeana in response to anthropogenic habitat alteration[END_REF][START_REF] Singh | Behavioural responses of lion-tailed mcaques (Macaca silenus) to a changing habitat in a tropical rain forest fragment in the Western Ghats, India[END_REF][START_REF] Tsuji | Feeding strategies of primates in temperate and alpine forests: comparison of Asian macaques and colobines[END_REF][START_REF] Xiang | Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: adaptations to a marginal environment[END_REF].

Even species broadly and stereotypically described as dietary specialists are able to modify their dietary composition in response to habitat change (folivores such as colobines, [Grueter et al., 2009b;[START_REF] Koenig | Socioecology of Hanuman langurs: The story of their success[END_REF][START_REF] Sayers | Himalayan Semnopithecus entellus at Langtang National Park, Nepal: diet, activity patterns, and resources[END_REF][START_REF] Sayers | Optimal foraging on the roof of the world: Himalayan langurs and the classical prey model[END_REF][START_REF] Xiang | Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: adaptations to a marginal environment[END_REF], or frugivores [START_REF] Russo | A multi-forest comparison of dietary preferences and seed dispersal by Ateles spp[END_REF][START_REF] Wieczkowski | Shifting forest composition and primate diets: A 13-year comparison of the Tana River Mangabey and its habitat[END_REF]). In addition, the Nelly Ménard ability of monkeys to persist despite anthropogenic land transformation includes their ability to exploit resources from cultivated land or secondary habitats resulting from deforestation [START_REF] Anderson | Does the matrix matter? A forest primate in a complex agricultural landscape[END_REF][START_REF] Campbell-Smith | Raiders of the lost bark: orangutan foraging strategies in a degraded landscape[END_REF][START_REF] Naughton-Treves | Temporal patterns of cropraiding by primates: linking food availability in croplands and adjacent forest[END_REF][START_REF] Quéméré | A DNA metabarcoding study of a primate dietary diversity and plasticity across its entire fragmented range[END_REF].

Primate species living in temperate habitats should be considered amongst the most flexible primate because their habitats are characterized by marked seasonality of resource quality and abundance [START_REF] Hanya | Altitudinal and seasonal variations in the diet of Japanese macaques in Yakushima[END_REF][START_REF] Hill | Seasonal variation in the feeding behavior and diet of Japanese macaques (Macaca fuscata yakui) in lowland forest of Yakushima[END_REF][START_REF] Hill | Climatic determinants of diet and foraging behaviour in baboons[END_REF][START_REF] Tsuji | Effects of yearly change in nut fruiting on autumn home-range use by Macaca fuscata on Kinkazan island, Northern Japan[END_REF][START_REF] Van Schaik | Seasonality in primate ecology, reproduction, and life history: an overview[END_REF]]. In addition, seasonal variation in fruit production is higher in temperate forests than in tropical forests [START_REF] Hanya | Fruiting and flushing phenology in Asian tropical and temperate forests: implications for primate ecology[END_REF], and fleshy fruit may be scarce for some temperate monkey species compared with tropical monkeys [START_REF] Hanya | Fruit fall in tropical and temperate forests: implications for frugivore diversity[END_REF][START_REF] Hanya | Dietary adaptations of temperate primates: comparisons of Japanese and Barbary macaques[END_REF][START_REF] Ting | Global patterns in fruiting seasons[END_REF].

Terrestrial or semi-terrestrial primate species, except the specialist graminivorous gelada baboons (Theropithecus gelada, [START_REF] Dunbar | Adaptation to grass-eating in gelada baboons[END_REF], also have a highly omnivorous and flexible diet (several macaque species, [START_REF] Ménard Goldstein | Ecology of rhesus macaques (Macaca mulatta) in northwest Pakistan[END_REF][START_REF] Hill | Seasonal variation in the feeding behavior and diet of Japanese macaques (Macaca fuscata yakui) in lowland forest of Yakushima[END_REF][START_REF] Zhao | Etho-ecology of Tibetan macaques at Mount Emei, China[END_REF]; baboons, [START_REF] Alberts | The evolutionary past and the research future: environmental variation and life history flexibility in a primate lineage[END_REF][START_REF] Wahungu | Diet and habitat overlap in two sympatric primate species, the Tana crested mangabey Cercocebus galeritus and yellow baboon Papio cynocephalus[END_REF][START_REF] Whiten | Dietary and foraging strategies of baboons[END_REF][START_REF] Whiten | The behavioral ecology of mountain baboons[END_REF]). In addition, some of them extract a great amount of their resources from the herbaceous layer: as a result, they rank among the species most vulnerable to competition with domestic herbivores with domestic herbivores (e.g. [START_REF] Sauther | The impact of fallback foods on wild ring-tailed lemur biology: a comparison of intact and anthropogenically disturbed habitats[END_REF]. Their diet flexibility is critical in allowing them to withstand habitat degradation and competition with domestic herds.

The Barbary macaque (Macaca sylvanus) is listed as "Endangered" on the Red List of Threatened Species, Appendix II of CITES [IUCN, 2013]. It is a terrestrial primate found primarily in extreme temperate regions, in mountain forests, similarly to Japanese macaques (Macaca fuscata, [START_REF] Nakayama | Feeding rates and energy deficits of juvenile and adult Japanese monkeys in a cool temperate area with snow coverage[END_REF]), rhesus macaques (M. mulatta, [START_REF] Qu | Rhesus monkeys (Macaca mulatta) in the Taihang mountains, Jiyuan county, Henan, China[END_REF]) and snub-nosed monkeys (Rhinopithecus roxellana and R. bieti, [START_REF] Grueter | Overwintering strategy of Yunnan snub-nosed monkeys: adjustments in activity scheduling and foraging patterns[END_REF]Su et Nelly Ménard al., 1998]). Barbary macaque habitats are characterized by marked monthly variation in resource availability. In these habitats the snowy periods last several months, during which the available resources are mostly restricted to mature leaves of evergreen trees and lichens. A second period of food scarcity occurs during the summer months when herbaceous plants dry up [START_REF] Ménard | Disponibilités et utilisation des ressources par le magot; (Macaca sylvanus) dans différents milieux en Algérie (in French with English summary)[END_REF][START_REF] Ménard | Behavioral responses of Barbary macaques (Macaca sylvanus) to variations in environmental conditions in Algeria[END_REF]. Barbary macaques in different habitat types have a highly flexible diet. As months go by, they can shift from a mostly insectivorous diet to a granivorous, and finally a folivorous diet [START_REF] Mehlman | Food resources of the wild Barbary macaque (Macaca sylvanus) in high altitude fir forest, Ghomaran Rif, Morocco[END_REF][START_REF] Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: I-régime en chênaie décidue (in French with English summary)[END_REF][START_REF] Ménard | Bark stripping and water availability: a comparative study between Moroccan and Algerian Barbary macaques (Macaca sylvanus)[END_REF][START_REF] Ménard Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: II-régime en forêt sempervirente et sur les sommets rocheux (in French with English summary)[END_REF].

Most wild Barbary macaque populations live in cedar-oak forests [START_REF] Fa | The distribution and current status of the Barbary macaque in North Africa[END_REF]. The largest population is located in the Middle Atlas in Morocco while other smaller populations are located in the cedar-oak forests of Algeria. The Middle Atlas forest presently suffers from heavy human pressure mainly due to overgrazing by sheep and goats [START_REF] Lamb | Human impact on the vegetation of the Middle Atlas, Morocco, during the last 5000 years[END_REF]. As Barbary macaques spend more than 50% of their mean annual feeding time on resources from the herbaceous layer [START_REF] Ménard Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: II-régime en forêt sempervirente et sur les sommets rocheux (in French with English summary)[END_REF], domestic herbivores such as sheep and goats that feed on the herbaceous plants are severe ecological competitors. Indeed, in forests where overgrazing was the highest, Barbary macaques increased their foraging and moving time, as well as daily travel distances (i.e. their energy costs), and spent less time feeding (i.e. ingesting food) than monkeys in less disturbed forests [START_REF] Ménard | Effect of habitat quality on ecological behaviors of a temperate-living primate: time budget adjustments[END_REF]. Moreover, a recent study shows a negative correlation between livestock grazing intensity and monkey density, which suggests that monkeys could no longer find enough resources in forests where grazing pressure was high [START_REF] Ménard | Impact of human pressure and forest fragmentation on Moroccan Barbary macaque (Macaca sylvanus) populations[END_REF].

In this paper, we describe the resource availability and diet of Barbary macaques living in three temperate cedar-oak forests undergoing varying intensities of livestock grazing.

Because of the high seasonality of temperate habitats, we expected to find strong inter-month diet variation in all three forests. We expected that intense grazing by sheep and goats would Nelly Ménard reduce the abundance and species richness of the herbaceous plants. As a corollary, we hypothesized that in the forest undergoing the most intense grazing pressure, monkeys would harvest their food more from the tree and shrub layers and/or use subterranean resources more than monkeys in the less heavily grazed forests. We also expected lower herbaceous plant species richness in their diet.

METHODS

Study sites, monkey groups and recording periods

The study sites were located in Algeria and Morocco. In Algeria, the Djurdjura National Park is located 4°8'E, 36°27'N, between 1100m and 1999m above sea level. It was created in 1983. In Morocco, the site of Aïn Kahla is located 5°12'W, 33°14'N and about 2000m above sea level, and the site of Seheb is located 5°14'W, 33°21'N, and 1500m above sea level.

These two sites were located in the National Park of Ifrane, created in 2004 in the Middle Atlas. We studied one focal group per site. Group sizes ranged between 38 and 47 individuals in Djurdjura, 18 and 24 individuals at Aïn Kahla, and between 19 and 33 individuals at Seheb. Their home ranges were estimated to be 2.8 km² in Djurdjura [START_REF] Ménard | Demography and ecology of Barbary macaques (Macaca sylvanus) in two different habitats[END_REF], 1.8 km² at Aïn Kahla and 2.6 km² at Seheb [Ménard et al., unpublished data]. All home ranges mainly (> 70%) comprised mixed cedar-oak forests, oak forests, or cedar forests. Djurdjura site was composed of four vegetation types including 63% cedar-oak forest, 10% pure oak coppices, 24% open grassland, and 3% shrubby formation [START_REF] Ménard | Disponibilités et utilisation des ressources par le magot; (Macaca sylvanus) dans différents milieux en Algérie (in French with English summary)[END_REF]. At Aïn Kahla and Seheb, we used a vegetation map from a study carried out in Ifrane park by a consulting agency whose information was checked before use [Sogreah-Ttoba, 2004].

According to that map, the two groups' home ranges (Aïn Kahla and Seheb) included more than 98% forests while open grasslands occupied less than 2%, and there were no pure oak coppices. Nelly Ménard Livestock grazing was prohibited and almost absent in Djurdjura, intermediate at Aïn Kahla, and intense at Seheb. At each site, an estimate of the grazing pressure was available for each "parcel" referenced by foresters and was drawn from Sogreah-Ttoba reports [Sogreah-Ttoba, 2004]. A "parcel" is a delimited area subjected to a uniform management program by forestry managers. Each parcel, including those in the home ranges of our groups, was characterized by an index ranging from 0 (minimum pressure: < 2 small ruminants (sm)/ha/day) to 2 (intense pressure: > 5 sm/ha/day). Observers verified this classification during the years of the study (2006)(2007)(2008).

Data collection

We estimated visually the percentage of cover (0-10%; 11-25%; 26-50%; 51-75%; > 75%) of each tree and shrub species (i.e.. their abundance) in 25-m radius plots located at the corners of 50m x 50m grid cells covering a broad proportion of the groups' home ranges (580 plots in Djurdjura, 291 at Aïn Kahla and 432 at Seheb). Their overall surface represented 32-40% of the home range areas. We used the median values of the cover classes to calculate the mean percentage cover of each species at the three sites.

We studied herbaceous species richness in spring at the peak of vegetation growth, and monthly variation in herbaceous abundance from February to August in the three sites. These measurements were carried out in 2008 at Aïn Kahla and Seheb and were drawn from a study conducted in 1984 in Djurdjura [START_REF] Ménard | Disponibilités et utilisation des ressources par le magot; (Macaca sylvanus) dans différents milieux en Algérie (in French with English summary)[END_REF][START_REF] Ménard | Demography and ecology of Barbary macaques (Macaca sylvanus) in two different habitats[END_REF]. We Nelly Ménard estimated species richness in 1m x 1m quadrats (47 in Djurdjura, 7 each at Aïn Kahla and Seheb) placed at the intersection of a 200-m grid covering the group's home range in Djurdjura, and every 200m along a 1.2-km transect in each home range of the Aïn Kahla and Seheb groups. We sampled fewer quadrats at Aïn Kahla and Seheb than at Djurdjura owing to lower diversity of vegetation types in the groups' home ranges (see above). In each quadrat, we recorded the presence/absence of each species. In addition, we recorded more occasional species (not found during quadrat sampling) ad libitum when observers moved around in the field. During monthly replicates, we measured global herb cover (%) as an indicator of monthly and inter-site variation in herbaceous abundance. In Djurdjura, monthly replicates were limited to 23 of the 47 quadrats due to schedule constraints related to behavioral observations. In doing so, however, we lost little in relative precision (defined as the ratio of the half-size of the confidence interval at alpha=0.05, 2.08% of the estimate of the herbaceous cover), which ensured a good approximation of the herb cover while dividing the sampling effort by two.

We conducted behavioral observations from dawn to dusk, and equalized observation times across the daylight hours. We recorded a total of 477, 890 and 750 hours of observations from the Djurdjura, Aïn Kahla and Seheb groups, respectively. Visibility was good at all sites, and animals were habituated to observers, who typically approached them as close as 3-10m. We collected diet data (plant names and parts eaten) by scan sampling, at 15min intervals [START_REF] Altmann | Observational study of behavior: sampling methods[END_REF], of five individuals observed from a right to left direction to avoid food item bias. We recorded food items at each feeding occurrence, i.e. the picking and ingestion of food items (foraging excluded). We categorized individuals as follows: adult males and females, more than 5 years old; sub-adult individuals, 3 and 4 years old; juveniles, 1 and 2 years old. To obtain as complete a record as possible of diet composition, we also Nelly Ménard recorded ad libitum rarely eaten food species that were not observed during the scan sampling procedure. These qualitative observations were not included in the statistical analysis.

Data analyses and statistics

The herbaceous plant sampling effort varied between the three sites. Because the observed number of species depends on sample size, our estimations of herbaceous species richness were standardized for comparisons. We produced sample-based rarefaction curves, which are plots of randomized richness vs. sampling effort, i.e. the number of quadrats [START_REF] Gotelli | Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness[END_REF]. Rarefaction generated the expected number of herbaceous species in sets of n sampled quadrats as well as the 95% confidence intervals. We used Mao Tau randomizations computed with EstimateS [START_REF] Colwell | Interpolating, extrapolating, and comparing incidencebased species accumulation curves[END_REF]. We then compared average species richness per sampling unit over the three sites using randomization tests.

Computations required Monte Carlo re-sampling [START_REF] Manly | Randomization and Monte Carlo methods in biology[END_REF], so we used the rich package (function c2m) in R [START_REF] Rossi | rich: an R package to analyse species richness[END_REF]. We also approximated the "true species richness" computing Chao2 estimators with EstimateS [START_REF] Colwell | EstimateS: Statistical estimation of species richness and shared species from samples[END_REF].

We used Generalized Linear Models (GLMs) and analysis of deviance (anova function in R [R Development Core Team, 2010]) to test for the effects of month and site on the percentages of herb cover (i.e. the monthly means of the sampled quadrats). We analyzed all subsets of models containing the 'month' and/or 'site' predictors (Table 1). GLMs used binomial errors for proportion data and a logit-link function [START_REF] Mccullagh | Generalized linear models[END_REF]]. We based model selection on Akaike's information criterion corrected for small samples (AICc, [START_REF] Burnham | Model selection and multimodel inference: a practical information -theoretical approach[END_REF]). We chose the model with the lowest AICc as the best fitting and the most parsimonious one. We calculated the Akaike weight (w i ) for each model, which can be interpreted as the probability for model i to be the best model to explain the observed variation in plant cover. Models with an AICc difference below 2 (ΔAICc <2) have substantial support and should be considered [START_REF] Burnham | Model selection and multimodel inference: a practical information -theoretical approach[END_REF]. Variable importance was Nelly Ménard estimated by summing the Akaike weights across models containing each predictor variable [START_REF] Burnham | Multimodal inference: understanding AIC and BIC in model selection[END_REF]. We used MuMIn package in R (function model.avg) for these calculations.

We expressed the composition of monthly diets as the percentage of time spent feeding on food species (Appendix A) and on 10 food categories (above-ground herbaceous resources, cedar seedlings, leaves and flowers of trees and shrubs, shrub fruit, acorns, roots, mushrooms, subterranean invertebrates, cedar bark, lichens). Subterranean invertebrates are ant's larvae, adults or eggs of earwigs, or earthworms. Cedar bark is the inner cambium and phloem through which the sap flows. Owing to diverging diets depending on Barbary macaques' age and sex classes [START_REF] Ménard | Behavioral responses of Barbary macaques (Macaca sylvanus) to variations in environmental conditions in Algeria[END_REF], we calculated mean monthly diet as the average of the mean diet of the four age/sex categories (adult male, adult female, subadult individual, juvenile individual). We pooled observations from the same month across the years. We calculated a mean diet for the study period by averaging the monthly values for each food category.

We produced sample-based rarefaction curves and computed Chao2 estimators to compare herbaceous species richness to the "true species richness" of the diets [START_REF] Colwell | EstimateS: Statistical estimation of species richness and shared species from samples[END_REF]. Rarefaction generated the expected number of species eaten in sets of n sampled hours that included feeding occurrences. We then plotted the randomized number of species as a function of the number of eaten food items as computed with EstimateS. We tested diet richness differences between sites using function c2m (rich package, [R Development Core Team, 2010;[START_REF] Rossi | rich: an R package to analyse species richness[END_REF]).

We used MANOVA with Roy test to investigate the effect of month, site, and the additive effect of 'month and site' on the percentage of time spent feeding on the 10 food categories [R Development Core Team, 2010]. We transformed our data, which consisted of proportions, using the arcsine square root. This transformation normalized the proportions. Nelly Ménard Our research was consistent with the Principles for the Ethical Treatment of Non Human Primates of the American Society of Primatologists. Data collection was based on non-invasive behavioral observations. All investigations reported in this manuscript comply with the current law in Morocco and Algeria and were conducted in close partnership with Moroccan Forestry authorities and the managers of the Djurdjura National Park in Algeria.

RESULTS

Vegetation characteristics and resource availability

At all three sites, the tree layer was dominated by cedars (Cedrus atlantica, 50% cover in Djurdjura, 57% at Aïn Kahla, 66% at Seheb) while holm oak (Quercus rotundifolia) was the second most common species (23% in Djurdjura, 53% at Aïn Kahla, 21% at Seheb). Other species (Pinus clusiana, P. halepensis, Populus nigra in Djurdjura; Acer monspessulanum, Sorbus torminalis at Aïn Kahla and Seheb) occupied less than 7% of the tree cover.

Global shrub cover in the monkeys' home ranges was greater in the Moroccan forests (44% at Aïn Kahla and 45% at Seheb) than in Djurdjura (14%). However, species richness was highest in Djurdjura (26 species), intermediate at Aïn Kahla (11 species) and lowest at Seheb (8 species). Only six species were common to the three sites. None of the rarefaction curves (Fig. 1) reached true herbaceous species richness. Estimated species richness (using Chao2 estimator) was 203 species in Djurdjura, 99 at Aïn Kahla and 33 at Seheb. When we added the species observed ad libitum, variation among sites remained similar (240, 107 and 41 species, respectively). Comparing species richness based on a standardized number of quadrats (N = 7), we found significantly higher richness values in Djurdjura than in Seheb, and in Aïn Kahla than in Seheb (Monte Carlo randomization test: P < 0.01), while we failed to detect a significant difference between Djurdjura and Aïn Kahla (P = 0.39). Nelly Ménard

The model that best explained variation in herbaceous plant cover included month, site and the interaction between month and site (Table 1). The sum of all Akaike weights showed 'month' and 'site' as equally important predictors (Sum(wAICc) = 1.00, Table 1). Monthly variation was significant (χ² = 1424.97, df=6 , P < 0.001) but differed significantly among sites, with plant cover reaching a peak in April at Aïn Kahla and Seheb and in May in Djurdjura (χ² = 604.34, df = 12, P < 0.001; Fig. 2). Plant cover varied significantly across sites (χ² = 285.39, df = 2, P < 0.001) : it was lower at Seheb than at the two other sites and lower in Djurdjura than at Aïn Kahla (Table 1).

Diet composition

We made a total of 2027, 4654 and 3205 feeding records from the Djurdjura, Aïn Kahla and Seheb groups, respectively. At all three sites, tree products in the monkeys' diets mainly came from the two dominant species, i.e. Cedrus atlantica and Quercus ilex. At Seheb and Aïn Kahla, Barbary macaques consumed barely half as many shrub species as compared to Djurdjura macaques (see details in appendix A). Comparing herbaceous species richness at a standardized number of hours of recordings (N = 191) we found a significantly richer diet in Djurdjura vs. the two other sites and in Aïn Kahla vs. Seheb (Fig. 3, Monte Carlo randomization tests: P < 0.01, see also details in appendix A). Estimated species richness (using Chao2 estimator) was 65 species in Djurdjura, 49 at Aïn Kahla and 31 at Seheb. In Djurdjura, this value approximates the true diet richness (74 herbaceous plant species, see also appendix A) obtained when rarely eaten species, observed ad libitum, were included.

In each site, more than 79% of the herbaceous species of the diet were recorded in the quadrats. Each of the remaining species composed less than 0.05% of the monthly diet. Thus the sampled quadrats reflected quite well the herbaceous species available for monkeys in their respective habitats. Nelly Ménard Diets varied significantly by month and by site (Fig. 4). The model with the lowest AICc included 'month + site' (MANOVA, month : F 6,12 = 24.03, P < 0.001; site : F 2,12 = 13.39, P < 0.001).

Variation in the monkeys' diet was explained by strong monthly changes in the proportions of almost all food categories (Fig. 4, Table 2). During winter months and in early spring (from February to April), the staple foods were above-ground herbaceous resources and/or cedar seedlings at all three sites (Fig. 4). In the following months (from May to August) monkeys consumed an increasing proportion of different subterranean resources (roots, mushrooms, invertebrates), shrub fruit, and/or acorns (Fig. 4). Consumption of cedar bark peaked at 18% in May at Aïn Kahla and 21% in June at Seheb. Monkeys' diets in Djurdjura and at Aïn Kahla relied significantly more on the aboveground herbaceous resources (58.3% and 47.6% on average, respectively) than at Seheb (22.3%, Fig. 4, Table 2). By contrast, among the subterranean resources, Seheb monkeys ate significantly more mushrooms (13.3% on average) and invertebrates (ant larvae, adults or eggs of earwigs, or earthworms; 6.9%), than monkeys at the two other sites (mushrooms < 3%; invertebrates < 1%). In parallel, they consumed significantly less roots (4.6% on average) than in Djurdjura (9.7%, Fig. 4, Table 2). This inter-site variation in the consumption of the different subterranean resources categories and of above-ground herbaceous resources was especially marked in late spring and summer (June to August, Fig. 4). The contribution of the tree and shrub resources (leaves and flowers, acorns, cedar seedlings, fruit) and lichens in the diets did not differ significantly between the three sites (Table 2). Although cedar bark was eaten only at Aïn Kahla and Seheb, our results only suggest a tendency toward differential cedar bark consumption between these two sites and Djurdjura (P = 0.08, Table 2, Fig. 4), possibly because of a lack of statistical power. Consumption of cedar male flowers also varied among sites, although it was not a major food class. It contributed to the monkeys' diet at Aïn Nelly Ménard Kahla and Seheb (up to 12% in August) while it was never observed in the diet of Djurdjura monkeys (Appendix A). Lichens were also a minor food item (~ 1.5% of the diet on average), but did contribute at all three sites.

DISCUSSION

Influence of human pressure and seasonality on habitat quality

In the Moroccan forests where grazing was intense (Seheb), plant species richness, especially herbaceous plant richness, was lower than in the other less intensively grazed forests of Djurdjura and Aïn Kahla. The high species richness in Djurdjura reflects a greater variety of vegetation types as well as the absence of grazing pressure. The abundance of herbaceous plants, in terms of herb cover, was also lowest in the forest undergoing the most intense grazing pressure (Fig. 2). Differences in species richness and abundance at the herbaceous layer level were already apparent when vegetation sprouted in February-March, before grazing started. Because of its long-term effects on vegetation [START_REF] Chaideftou | Seed bank composition and above-ground vegetation in response to grazing in sub-Mediterranean oak forests (NW Greece)[END_REF], intense grazing pressure is probably the main factor that accounts for these differences between sites, in particular between Aïn Kahla and Seheb where forest formations were relatively comparable among the groups' home ranges. Indeed, overgrazing severely and durably reduced herb species richness and abundance in other Mediterranean forests [START_REF] Chaideftou | Seed bank composition and above-ground vegetation in response to grazing in sub-Mediterranean oak forests (NW Greece)[END_REF]. Based on grazing intensity, we did not expect overall greater abundance of herbaceous plants at Aïn Kahla vs. Djurdjura. This difference may reflect climate differences. Snow persisted until March in Djurdjura, and herbaceous growth started two months later than at Aïn Kahla and Seheb. In addition, the plant cover dried earlier in Djurdjura (Fig. 2).

Seasonal dietary flexibilityimportance of subterranean resources

Seasonal dietary flexibility has been described in many primate species in tropical as well as in temperate regions (see review in [START_REF] Ménard Hemingway | The influence of seasonality on primate diet and ranging[END_REF]). Like other Nelly Ménard monkeys living in temperate habitats (e.g. [Grueter et al., 2009b;[START_REF] Guo | Diet and activity budget of Rhinopithecus roxellana in the Qinling Mountains, China[END_REF][START_REF] Hanya | Altitudinal and seasonal variations in the diet of Japanese macaques in Yakushima[END_REF][START_REF] Hill | Seasonal variation in the feeding behavior and diet of Japanese macaques (Macaca fuscata yakui) in lowland forest of Yakushima[END_REF][START_REF] Tsuji | Long-term variation in fruiting and the food habits of wild Japanese macaques on Kinkazan Island, northern Japan[END_REF][START_REF] Van Doorn | The effects of extreme seasonality of climate and day length on the activity budget and diet of semi-commensal chacma baboons (Papio ursinus) in the Cape Peninsula of South Africa[END_REF]), the macaques we studied showed marked monthly variation in their diet. It consisted of rapid adjustments to abrupt changes in food availability that characterize extreme temperate environments where most productions (budding, flowering, fruiting, and seed production) are highly synchronized. Our results are in line with studies of Barbary macaques in other habitat types (deciduous oak forest, [START_REF] Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: I-régime en chênaie décidue (in French with English summary)[END_REF]; fir forest [START_REF] Mehlman | Food resources of the wild Barbary macaque (Macaca sylvanus) in high altitude fir forest, Ghomaran Rif, Morocco[END_REF]), which suggest general patterns of seasonal dietary changes for the species. In particular, Barbary macaques use a large amount of subterranean resources in the dry months of food scarcity (up to > 56% in cedar-oak forest, this study, Fig. 4; up to > 34% in deciduous oak forest, [START_REF] Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: I-régime en chênaie décidue (in French with English summary)[END_REF], common in fir forest, [START_REF] Mehlman | Food resources of the wild Barbary macaque (Macaca sylvanus) in high altitude fir forest, Ghomaran Rif, Morocco[END_REF]). This diet shift also occurs in other temperate/terrestrial species such as savannah baboons (up to 53% of the diet, [START_REF] Alberts | Seasonality and long-term change in a savanna environment[END_REF][START_REF] Whiten | Dietary and foraging strategies of baboons[END_REF]), and to a lesser extent Himalayan gray langurs (up to 13% [START_REF] Sayers | Himalayan Semnopithecus entellus at Langtang National Park, Nepal: diet, activity patterns, and resources[END_REF]), and snub-nosed monkeys (low quantities, [Grueter et al., 2009b]). By contrast, this shift is less common in tropical primates : underground resources represent very low quantities in their diet, even in tropical forest baboons' diet [START_REF] Kunz | Changes in baboon feeding behavior: Maturity-dependent fruit and seed size selection within a food plant species[END_REF]. Although other temperate macaques share similar patterns of diet seasonality with Barbary macaques, to our knowledge few of them rely on underground resources (see a review in [START_REF] Ménard | Do ecological factors explain variations in macaque social organisation?[END_REF]), except, to a lesser extent, Macaca mulatta (23.7% in winter, [START_REF] Ménard Goldstein | Ecology of rhesus macaques (Macaca mulatta) in northwest Pakistan[END_REF]]), M. fuscata (< 3% during the dry winter season, [START_REF] Hanya | Diet of a Japanese macaque troop in the coniferous forest of Yakushima[END_REF]), and M. munzala (6.7% of winter food includes roots, tubers, stems and sepals taken together [START_REF] Mendiratta | Winter ecology of the Arunachal macaque Macaca munzala in Pangchen valley, Western Arunachal Pradesh, Northeastern India[END_REF]). Therefore, some diet characteristics of M. sylvanus appear closer to savannah baboons' than to most other macaque species'.

Influence of habitat quality on diet Nelly Ménard

As a consequence of differences in habitat quality between the sites, the specific richness of the monkeys' diet was lower in the forest undergoing most grazing (Seheb).

Lower diet diversity was also observed in Rhinopithecus bieti [START_REF] Xiang | Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: adaptations to a marginal environment[END_REF] and in M. tonkeana [START_REF] Riley | Flexibility in diet and activity patterns of Macaca tonkeana in response to anthropogenic habitat alteration[END_REF] in poor habitats whereas anthropogenic landscape alteration did not influence diet richness of golden-crowned sifakas (Propithecus tattersalli) thanks to their ability to utilize both forest fragments and matrix habitats [START_REF] Quéméré | A DNA metabarcoding study of a primate dietary diversity and plasticity across its entire fragmented range[END_REF]. Therefore, the way habitat quality affects diet richness may depend on monkeys' ability to adapt to new habitats or to exploit new compartments of their environment.

Our results suggest that Barbary macaques prefer above-ground herbaceous resources, when available, rather than arboreal or shrub resources (e.g. cedar leaves that were abundant in all study sites). Indeed, in the site least affected by livestock, where cedars (and likely cedar foods) were as available as in the overgrazed forest, monkeys preferred to eat herbaceous plants, and they consumed them two times more (>48% on average) than in overgrazed forest (22%, Fig. 3). Therefore, herbaceous plants appear as a limiting resource.

In the site where grazing pressure was high and above-ground herbaceous resources were scarce, monkeys' diets included more subterranean than above-ground herbaceous foods (25% vs. 22% on average, Fig. 4, Table 2). In addition, they compensated for the reduced above-ground herbaceous resources by preferentially exploiting the subterranean layer rather than shifting to arboreal and shrub resources. Therefore, these results suggest that monkeys adjusted their diet according to the availability of herbaceous resources. In the least grazed sites, monkeys devoted five times less time to feeding on subterranean resources than on above-ground plants.

In the two grazed forests of the Middle Atlas (Aïn Kahla and Seheb), we noticed the consumption of cedar bark, cedar strobiles, earthworms and earwigs. This had never been observed in the preserved cedar-oak forest of Djurdjura (Appendix A, [Ménard & Vallet, Nelly Ménard 1988]; Ménard andVallet, unpublished data from behavioral studies conducted between 1985 and[START_REF] Qu | Rhesus monkeys (Macaca mulatta) in the Taihang mountains, Jiyuan county, Henan, China[END_REF]. Earthworms and earwigs were also unknown monkeys' invertebrate preys in the deciduous oak forest of Akfadou in Algeria where livestock were almost absent ( [START_REF] Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: I-régime en chênaie décidue (in French with English summary)[END_REF]; Ménard andVallet, unpublished data from behavioral studies conducted between 1985 and1992). By contrast, previous studies mentioned the presence of cedar bark, cedar strobiles and earthworms in monkey's diet in cedar forests of the Middle Atlas [START_REF] Deag | Feeding habits of Macaca sylvanus (Primates: Cercopithecinae) in commercial Moroccan cedar forest[END_REF][START_REF] Drucker | The feeding ecology of the Barbary macaque and cedar forest conservation in the Moroccan Moyen Atlas[END_REF] and in a fir forest of the Rif in northern Morocco [START_REF] Mehlman | Food resources of the wild Barbary macaque (Macaca sylvanus) in high altitude fir forest, Ghomaran Rif, Morocco[END_REF] that underwent heavy grazing by livestock. It appears that Barbary macaques fed on a separate niche from domestic herbivore competitors in the herbaceous layer in grazed forests. This implies innovative ways of acquiring alternative foods, from the underground or arboreal layer (e.g. extractive foraging for subterranean invertebrates or sucking cedar strobiles to ingest the resin before rejecting them). Interestingly, [START_REF] Mehlman | Food resources of the wild Barbary macaque (Macaca sylvanus) in high altitude fir forest, Ghomaran Rif, Morocco[END_REF] describes another innovative feeding technique in the fir forest of the Rif, i.e. "tadpole fishing" in the shallow pools of the streams.

These findings highlight dietary flexibility as a key element for Barbary macaques to cope with changing environments.

In all three sites, acorns were an extensive component of the diet in August. Ménard and Vallet showed that acorns can constitute a staple food at least for four months and can be eaten from July (unripe acorns) to March (fallen acorns found under fallen leaves or snow) in evergreen cedar-oak or in deciduous oak forests [START_REF] Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: I-régime en chênaie décidue (in French with English summary)[END_REF][START_REF] Ménard Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: II-régime en forêt sempervirente et sur les sommets rocheux (in French with English summary)[END_REF]. Similar patterns were observed in a fir forest [START_REF] Mehlman | Food resources of the wild Barbary macaque (Macaca sylvanus) in high altitude fir forest, Ghomaran Rif, Morocco[END_REF]. These highly energetic food items, rich in soluble carbohydrates and fat, although not in protein [START_REF] Abbas | Landscape fragmentation generates spatial variation of diet composition and quality in a generalist herbivore[END_REF], enable monkeys to replenish their energy reserves before the winter months. Species of the genus Quercus or related genuses of the Fagaceae family (Cyclobalanopsis, Lithocarpus) provide comparable lasting key resources to other temperate primates (R. bieti, [Grueter et al., Nelly Ménard 2009a;[START_REF] Xiang | Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: adaptations to a marginal environment[END_REF]; R. roxellana, [START_REF] Guo | Diet and activity budget of Rhinopithecus roxellana in the Qinling Mountains, China[END_REF]; M. thibetana, [START_REF] Zhao | Natural foods and their ecological implications for Macaca thibetana at Mount Emei, China[END_REF]; M. fuscata, [START_REF] Agetsuma | Effects of habitat differences on feeding behaviors of Japanese monkeys: comparison between Yakushima and Kinkazan[END_REF][START_REF] Hill | Seasonal variation in the feeding behavior and diet of Japanese macaques (Macaca fuscata yakui) in lowland forest of Yakushima[END_REF]).

Did Barbary macaques rely on fallback foods?

Many species of primates overcome periods of food scarcity by relying on fallback foods when preferred items are unavailable (e.g. [START_REF] Marshall | Evolutionary consequences of fallback foods[END_REF]; grass corms during a dry summer, [START_REF] Altmann | Fallback Foods, Eclectic Omnivores, and the Packaging Problem[END_REF]; bark, lichens, invertebrates, or leaves during dry winters [Grueter et al., 2009b]).

Bark is included in the diet of many primate species to varying extents in tropical [START_REF] Chaves | Dietary flexibility of the brown howler monkey throughout its geographic distribution[END_REF][START_REF] Ménard | Diet and activity pattern of howler monkeys (Alouatta palliata) in Los Tuxtlas, Mexico: Effects of habitat fragmentation and implications for conservation[END_REF] and temperate habitats [Grueter et al., 2009b;[START_REF] Guo | Diet and activity budget of Rhinopithecus roxellana in the Qinling Mountains, China[END_REF][START_REF] Hanya | Diet of a Japanese macaque troop in the coniferous forest of Yakushima[END_REF][START_REF] Xiang | Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: adaptations to a marginal environment[END_REF][START_REF] Zhao | Natural foods and their ecological implications for Macaca thibetana at Mount Emei, China[END_REF]]. It appears as the most common fallback food for temperate primates in winter [Grueter et al., 2009b] and is also considered as an adaptation to extreme habitats in Rhinopothecus bieti [START_REF] Xiang | Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: adaptations to a marginal environment[END_REF].

In Barbary macaques, bark stripping occurred between May and August, and reached a maximum of about 20% of their feeding time. We observed a relatively high level of bark stripping even when herbaceous resources were plentiful, confirming previous findings from a preliminary study conducted in 1995 at Aïn Kahla [START_REF] Ménard | Bark stripping and water availability: a comparative study between Moroccan and Algerian Barbary macaques (Macaca sylvanus)[END_REF]. These findings suggest that bark is not a fallback food for Barbary macaques.

It takes a long time to process cedar bark compared to foods like herbaceous leaves or seeds (mean number of consumption units of a food per minute spent foraging and feeding: about six for bark vs. up to 48 for leaves and 33 for seeds; Ménard et al., unpublished data).

The consumption of bark, despite the long handling time and the availability of other resources, suggests that cedar sap may provide important nutrients unavailable in other foods.

Tree exudates consumed by various Callitrichidae or patas monkeys (Erythrocebus patas) are rich in calcium and can counter-balance a diet that is poor in that mineral [START_REF] Garber | Proposed nutritional importance of plant exudates in the diet of the Panamanian Tamarin, Saguinus oedipus geoffroyi[END_REF]Nelly Ménard Isbell et al., 2013;[START_REF] Smith | Composition and proposed nutritional importance of exudates eaten by saddleback (Saguinus fuscicollis) and mustached (Saguinus mystax) tamarins[END_REF]. Grazing pressure, which induces lower species richness in forests, can lead to a monotonous diet unlikely to span the whole range of the monkeys' nutritional needs. However, we need further analyses on the nutritional quality of bark and other food items to confirm this hypothesis. The increased bark stripping by monkeys noticed by foresters in the Middle Atlas over the last 20 years [START_REF] Et-Tobi | Changements climatiques, dégradations et dépérissements: arguments et nouveaux outils pour une réforme de la sylviculture des cédraies au Maroc[END_REF] may result from a grazing-induced decrease in herbaceous species diversity.

Lichens have been observed in the diet of other temperate monkeys as fallback foods during periods of food scarcity [Grueter et al., 2009b;[START_REF] Kirkpatrick | Snub-nosed monkeys: multilevel societies across varied environments[END_REF]. In Barbary macaques living in a deciduous oak forest, lichens composed up to 43% of the monthly diet in winter and 17% in summer, when preferred foods are relatively scarce [START_REF] Ménard | Le régime alimentaire de Macaca sylvanus dans différents habitats d'Algérie: I-régime en chênaie décidue (in French with English summary)[END_REF]. In this site, lichens could be fallback foods. At Aïn Kahla and Seheb, the limited consumption of lichens (< 3.2%) during periods of food shortage could reflect a low availability of this resource which is extensively harvested by local people for traditional medicine [START_REF] Bellakhdar | Repertory of standard herbal drugs in the moroccan pharmacopeia[END_REF].

Conclusions and perspectives regarding Barbary macaque foraging strategy

This study provides evidence of dietary flexibility in Barbary macaques. They survive in altered habitats by exploiting alternative food resources (e.g. subterranean foods or cedar bark) that escape from their main competitors, i.e. sheep and goats. At the same time, they avoid food items that are available year-round such as cedar leaves. However, by foraging on scarce, difficult-to-excavate foods, monkeys increase their energy costs by spending more time foraging and moving, and increasing group's day range lengths [START_REF] Ménard | Effect of habitat quality on ecological behaviors of a temperate-living primate: time budget adjustments[END_REF].

Our findings suggest that Barbary macaques adopt an energy-maximizing strategy in the summer period of food scarcity, confirming previous studies performed during a comparable time of year [START_REF] Ménard | Behavioral responses of Barbary macaques (Macaca sylvanus) to variations in environmental conditions in Algeria[END_REF]. Further studies on food handling time, daily dry weight intake and energy intake would be useful to assess the profitability of foods (energy/handling Nelly Ménard time, [START_REF] Sayers | Optimal foraging on the roof of the world: Himalayan langurs and the classical prey model[END_REF]), and to specify whether Barbary macaques' foraging strategies lead them to incorporate scarce but high-return foods in their diet. These developments would bring new, valuable knowledge for the preservation of the species.

Overgrazing, through its negative effects on habitat quality, depresses population density [START_REF] Ménard | Impact of human pressure and forest fragmentation on Moroccan Barbary macaque (Macaca sylvanus) populations[END_REF]. These findings suggest that, despite their dietary flexibility, monkeys may not cope fully with anthropogenic changes in their habitat. High levels of foraging effort may induce considerable energetic stress that affect female reproductive strategies [START_REF] Foerster | Seasonal energetic stress in a tropical forest primate: proximate causes and evolutionary implications[END_REF], especially by preventing successful lactation, and in turn inducing lower infant survival.

Maintaining sustainable populations of Barbary macaques in the Middle Atlas requires urgent changes in the management of forests, especially by reducing the number of grazing sheep and goats. Additionally, we recommend allowing holm oaks to fully develop in the Middle Atlas instead of using clear-cutting sylvicultural pratices in order to preserve the production of acorns, a crucial food resource for Barbary macaques before the stress of the winter season.

ACKNOWLEDGMENTS

Financial support for this study came from the contract "Service Provincial des Eaux et Forêts d'Ifrane/University of Rennes 1", with N. Ménard and M. Qarro as French and Moroccan scientific leaders, respectively. We thank the whole team of the Ifrane National Park project, Z. Amhaouch, I. Bouziane, B. Elasri, N. Elrouat, and L. Oukannou who provided help with logistics and encouragement when necessary. Our study was conducted in close partnership with the "Haut Commissariat aux Eaux et Forêts et à la Lutte contre la Désertification" and the Regional Director of "Eaux et Forêts du Moyen Atlas" at Meknes. We greatly appreciate the editorial work and the helpful comments of Marina Cords and the two other anonymous reviewers. We thank G. Hanya, C. Grueter and Y. Tsuji for fruitful discussions on the ecology Nelly Ménard of temperate primates. We are grateful to H. Whitfield who kindly revised the English of the first draft of the manuscript. We thank C. Corbier-Bartheaux, P. Collignon and J-N. Roulleau (French Agency for Development) for their consideration and support towards this study. This is a scientific production of UMR CNRS 6553, Caren-OSUR, University of Rennes1. Significant variations are given in bold. a When the variations involved significant difference between sites, the decomposition of the P value is specified. Nelly Ménard Appendix A. Specific composition of the Barbary macaque diet (as average of monthly percentages of feeding time) and monthly occurrences (x) at the three sites. For each species, the highest monthly percentage is given in parentheses and the associated month is indicated in bold. Number of years of observations 1 1 2 1 1 1 1 1 1 2 2 1 3 3 1 1 2 2 1 2 2 B, bark; F, fruit; Fl, flowers; Ms, male strobiles; L, leaves; R, roots; S, seeds; St, stem; Sg, seedlings; Ac, acorns; Ew, earthworms; Ewg, adults and eggs of earwigs; Al, ant larvae. Mushrooms included two hypogeous fungi (Geopora sumneriana and Tuber panniferum) at Aïn Kahla and Seheb and undetermined above-ground fungi in Djurdjura. + : <0.05% of feeding time or rarely eaten food items recorded ad libitum, out of the scan sampling observations.

FIGURE LEGENDS

  We carried out observations in Djurdjura between April 1983 and March 1985 (seven months, September to January excluded), at Ain Kahla between July 2006 and August 2008 (13 months, September-January excluded) and at Seheb between April 2007 and August 2008 (11 months, September-January excluded). Livestock entered the forest to graze from February to August, i.e. during the winter (February-March), spring (April-June) and summer (July-August) seasons.

Figure 1 :

 1 Figure 1: Herbaceous species richness in the three sites. Rarefaction curves represent the

Figure 2 :

 2 Figure 2: Monthly variation in herb cover (%) in the three sites. Bars represent standard

Figure 3 :

 3 Figure 3: Herbaceous species richness in the monkeys' diets at the three sites. Rarefaction

Figure 4 .

 4 Figure 4. Variation in the percentage of feeding time spent on 10 food categories depending

Fig

  Fig.1

Table I .

 I Comparisons of models of herb cover as a function of month and site, showing model selection statistics and results for inter-site comparisons. Akaike's information criterion corrected for small sample sizes; wi, Akaike's information criterion weights for each model; Sum(wAICc), the relative importance of predictor variables was assessed by summing the Akaike weights from each model containing that predictor. The highest values are in bold-type. Month x site stands for month + site + month:site (effect of month, plus effect of site plus effect of the interaction of month and site). See text for calculation details. Nelly Ménard TableII. Statistical analyses of the monthly and inter-site variations of monkey diets. Results of the MANOVA analyses of the additive model "month + site".

	Subsets of models Month * site a Month + site Month Site Djurdjura -Aïn Kahla Djurdjura -Seheb Aïn Kahla -Seheb Cedar bark Cedar seedlings Tree and shrub leaves and flowers Shrub fruits Above-ground herbaceous k Deviance AICc ΔAICc wi Sum(wAICc) Estimate SE z 21 1870.8 2767.3 0.00 1.0 9 2475.1 3343.9 576.6 0.0 7 2760.5 3625.0 857.7 0.0 1.0 3 3900.1 4756.2 1988.9 0.0 1.0 0.52 0.08 6.48 -0.85 0.12 -6.97 <0.001 P <0.001 -1.37 0.13 -10.59 <0.001 F 8,12 R² adj P value Inter-site Estimate a SE t P value 2.46 0.37 0.08 5.60 0.65 < 0.01 0.63 -0.17 0.74 2.34 0.35 0.09 resources 7.37 0.72 <0.001 Aïn Kahla-Seheb -0.29 0.08 -3.60 <0.01 Djurdjura-Seheb -0.41 0.08 -5.01 <0.001 Acorns 3.23 0.47 <0.05 AICc, Food items Roots 6.52 0.69 <0.01 Djurdjura--0.14 0.05 -2.53 <0.05
				Seheb
	Invertebrates	4.20 0.56 <0.05 Aïn Kahla-	0.12	0.05	2.54	<0.05
				Seheb
				Djurdjura-	0.20	0.05	4.01	<0.01
				Seheb
	Mushrooms	3.89 0.54 <0.05 Djurdjura-	0.30	0.07	4.53	<0.001
				Seheb
				Aïn Kahla-	0.20	0.07	2.97	<0.05
				Seheb
	Lichens	0.46	-	0.86
			0.27

a :


E Larose

M Campillo

A Khan

Y Nakamura

Katherine G Jackson

Lunar Subsurface Investigated from Correlation of Seismic Noise

By correlating seismic noise recorded by four sensors placed on the Moon during the Apollo 17 mission, we have retrieved a well-defined dispersed Rayleigh wave pulse. Inversion of its group velocity provides new constraints on the lunar subsurface structure. The estimated "signal-to-noise" ratio (SNR) of the retrieved Rayleigh wavetrain is strongly dependent on solar illumination, effectively making solar heating a source of seismic noise on the Moon. This result suggests that in future planetary missions it is feasible to extract information on the internal structure of extraterrestrial objects by correlating seismic noise even when natural quakes are absent.

The passive imaging technique is based on the timedomain cross-correlation of acoustic or seismic waves acquired at two passive sensors. The main assumption is that the cross-correlation yields the Green function (GF) between the receivers, i.e. the impulse response recorded at one sensor, with the other acting as source. Initial applications of the method include helioseismology, where it provided images of the Sun's interior [START_REF] Duvall | Time distance helioseismology[END_REF] and more recently, it has been tested in the ultrasonic domain using diffuse fields [START_REF] Lobkis | On the emergence of the Green functions in the correlations of a diffuse field[END_REF][START_REF] Derode | Recovering the Green's function from field-field correlations in an open scattering medium[END_REF][START_REF] Larose | Imaging from one-bit correlations of wideband diffuse wave fields[END_REF] as well as with noise [START_REF] Weaver | Ultrasonics without a Source: Thermal Fluctuation Correlations at MHz Frequencies[END_REF]. Passive imaging has also been achieved using seismic coda [START_REF] Campillo | Long range correlations in the diffuse seismic coda[END_REF] as well as seismic noise [START_REF] Shapiro | Emergence of broadband Rayleigh waves from correlations of the ambient seismic noise[END_REF][START_REF] Shapiro | High resolution surface wave tomography from ambient seismic noise[END_REF][START_REF] Sabra | Surface wave tomography from microseisms in southern California[END_REF] for frequencies ranging from 0.025 to 0.2 Hz. In the latter application it provided well-resolved images of the first 20 km of the subsurface beneath California. On Earth, these studies have shown that a statistical treatment of seismic noise yield the GF when averaged over sufficiently long time. Microseismic background noise is mainly excited by surface sources like oceanic and atmospheric perturbations [START_REF] Rhie | Excitation of Earth's continuous free oscillations by atmosphere-ocean-seafloor coupling[END_REF]. The purpose of the present paper is to take the passive imaging method beyond the Earth and apply it to extraterrestrial planets on which neither an ocean nor an atmosphere exists. In particular, our aim is to investigate the method in the case where the microseismic background noise is made of fully diffusive waves, at frequencies higher than previously investigated [START_REF] Shapiro | High resolution surface wave tomography from ambient seismic noise[END_REF].

The only solar system body other than the Earth from which we have seismic observations pertinent to its interior properties is the Moon. From 1969 to 1972 the US Apollo program installed one short-lived and four longlived seismic stations on the Moon. All but the first station were operated until 1977. The data collected by the Apollo seismic network provided the basis for a number of studies of lunar seismicity and internal structure pub-lished during the 1970s, early 1980s, and again recently [START_REF] Latham | Lunar structure and dynamics -Results from the Apollo passive seismic experiment[END_REF][START_REF] Toksöz | Structure of the Moon[END_REF]Nakamura et al., 1982;[START_REF] Khan | An Inquiry Into the Lunar Interior: A Non-Linear Inversion of the Apollo Lunar Seismic Data[END_REF][START_REF] Lognonné | A New Seismic Model of the Moon: Implications for Structure, Thermal Evolution and Formation of the Moon Earth Planet[END_REF]. In addition to the above passive seismic experiment, active seismic experiments were also carried out on missions 14, 16 and 17. The main objective was to infer the velocity structure of the uppermost part of the crust down to a few km depth using traditional seismic refraction techniques [START_REF] Cooper | Lunar near surface structure[END_REF].

Apollo 17 touched down on the floor of the Taurus-Littrow Valley near the southeastern rim of the Serenitatis Basin, which consists of irregular, heavily cratered regolith developed on lava flows partly filling an embayment between massifs 2 km high [START_REF] Heiken | Lunar Sourcebook -Users Guide to the Moon[END_REF]. The Apollo 17 Lunar Seismic Profiling Experiment (LSPE) was deployed on Dec. 14, 1972 at a distance of about 180 m W-NW of the lunar module. Four geophones, with natural resonant frequencies of 7.5 Hz, here labeled G1 to G4, were deployed in a triangular array (Fig. 1) and recorded the vertical ground velocity in the frequency range from 3 to 30 Hz during the landing mission in 1972 [START_REF] Kovach | Apollo 17 Preliminary Science Report[END_REF] and then again from August 1976 to April 1977. The geophones were simultaneously connected to the central station where the seismic signals S 1...4 (t) were sampled at 118 Hz and digitized before being telemetered to the Earth. Prior to conversion into a 7-bit digital format (counts 0 to 127), the signals were conditioned using a logarithmic compression, which was done to increase the dynamic range. A typical four-channel record is displayed in Fig. 1.

We processed continuous data from Aug. 15, 1976to Apr. 24, 1977. They are time-windowed into 2016 record samples, each lasting about T = 3 hours for a given record d. The correlated traces are calculated directly from the raw data without applying any decompression or correction filter. The absence of decompression tends to equalize the noise amplitude. For a given pair of geo- phones i, j, and the record d, a cross-correlated trace is determined as:

C d ij (τ ) = d+T d S i (t + τ )S j (t)dt (1)
Correlated traces are then filtered in the frequency range of interest (4-12 Hz). The central part of each trace |τ | < 0.5 s (cross-talking between geophones induces a peak at the correlation time τ = 0) is not displayed. Each trace is normalized by its maximum value. At the end we computed the average of the correlations over the set of records d. Typical results are displayed in Figs. 1, 2(a) and 3(a). A well-defined pulse is observed both for positive and negative correlation times τ . Why should this pulse emerge from the correlations? Seismic waves propagating in the direction j → i add up coherently in the correlation, and contribute to this well-defined pulse for times τ > 0 (causal part of the correlations). Seismic waves propagating in the opposite direction (i → j) contribute to the well defined pulse for times τ < 0 (acausal part of the correlations). Waves propagating in other directions add up incoherently and contribute to the residual fluctuations in the correlations [START_REF] Roux | Extracting coherent wavefronts from acoustic ambient noise in the ocean[END_REF].

The reconstructed pulses are interpreted as Rayleigh waves between geophones i and j, i.e. the ground velocity response of the subsurface at j to a vertical impulsive force at i. They are found to propagate with an average velocity of ∼50 m/s, and are clearly dispersive, as shown in Fig. 2(a). The group velocity is evaluated by picking the envelope arrival time of the Rayleigh pulse. This pulse is filtered around 14 different frequencies, ranging from 3.6 Hz to 11.4 Hz (33% bandwidth). Velocities were calculated when the signal-to-noise ratio (SNR) of the correlated traces is >2. When possible we averaged velocities over the three central pairs of geophones. The group velocity dispersion curve is plotted (dots) in Fig. 2(b). The uncertainties on observed velocities are estimated to be 5%. This dispersion curve is used to retrieve the shear velocity profile through iterative linearized inversion [START_REF] Herrmann | Computer Programs in Seismology: Surface Waves, receiver functions and crustal structure[END_REF]. A four layer model was assumed with variable thickness and velocities.The inverted shear-wave velocity profile is displayed in Fig. 2(c). The inversion was stopped once calculated data (Fig. 2(b), crosses) fit the observations (dots) within 3%. While obviously more complex models can be found, our chosen parameterisation reflects the minimum number of layers that were found needed to fit data. The velocity jump below 5 m depth is interpreted as the base of the lunar regolith, consisting of impact breccias. [START_REF] Cooper | Lunar near surface structure[END_REF], using travel time inversion of refracted P-waves, found that the compressional wave velocity beneath the Apollo 17 site was around 100 m/s from 0 to 4 m depth and 327 m/s from 4 to 32 m depth. Our shear wave profile thus complements their P-wave profile, giving the v P /v S ratio of the Lunar regolith at this site of ∼2. The present result is also consistent with the S-wave velocity profiles derived from the H/V spectral amplitude ratios at other Apollo sites [START_REF] Horvath | Lunar near-surface shear wave velocities at the Apollo landing sites as inferred from spectral amplitude ratios[END_REF], where they generally increase from 40 m/s at the surface to about 400 m/s at depths between 95 and 160 m.

As a curious feature of our correlations we found that the Rayleigh wave emergence is fluctuating with time of the year. To quantify these variations, we estimated the SNR of the correlated traces as a function of record date d. The signal level corresponds to the amplitude of the (causal or acausal) peak. The noise is defined as the standard deviation of the subsequent fluctuations from τ = ±2 s to τ = ±4 s (Fig. 3(a)). The SNR displayed in Fig. 3(b) is calculated for both the causal (red) and acausal (blue) part of the correlation. It is found to fluctuate with a periodicity of exactly 29.5 days which is also the lunation period. The SNR increases during daytime (displayed as thick horizontal bars on Fig. 3(b)) and decreases at night, pointing to an origin of the Rayleigh wave with solar illumination. When the sun heats the lunar surface, temperature increases from -170 • C to +110 • C [START_REF] Langseth | Apollo 17 Preliminary Science Report[END_REF], leading to very high vertical thermal gradients, and resulting in cracking of the lunar surface material and Rayleigh wave generation. This interpretation is in line with what was observed during the Apollo era where a large percentage of the seismic events were found to be very small moonquakes, termed thermal moonquakes, occurring with great regularity [START_REF] Duennebier | Thermal moonquakes[END_REF].

Their activity starts abruptly about 2 days after lunar sunrise and decreases rapidly after sunset, following essentially the same trend as the SNR we observed. Thus it is most likely that the signal we observed here is derived from thermal moonquakes.

The correlated traces displayed in Figs. 1 and 3(a) are not found to be symmetric in time. Though the pulse arrival times are symmetric, waveform amplitudes may change due to preferential direction of propagation of the incident wave field [START_REF] Van Tiggelen | Green Function Retrieval and Time Reversal in a Disordered World[END_REF][START_REF] Paul | Empirical synthesis of time-asymmetrical Green functions from the correlation of coda waves[END_REF]. The peak amplitude for each part of the correlations, and for each couple of geophones, is evaluated. Since the reconstructed peak amplitude is proportional to the intensity of the incident waves, we interpret this asymmetry as an anisotropy of the wavefield. Let us assume that the symmetric part of the traces is generated by an isotropic flux Φ 0 (waves coming from all directions onto the array), and furthermore that the asymmetric part, corresponding to the excess of amplitude observed on one part of the traces, is generated by an anisotropic flux Φ (preferential wave incidence). The peak amplitude is therefore proportional to Φ 0 ± 1 2 Φcos(θ i ) where θ i is the incident angle of the anisotropic flux onto the pair i -3 (Fig. 4). To quantify the asymmetry, we estimate the following ratio:

P + 3i -P - 3i P + 3i + P - 3i = Φ Φ 0 cos(θ i )
where P + 3i is the peak amplitude of the C 3i (τ ) positive part. Note that this ratio for pair 3 -4 can be deduced from Fig. 3(a). It should be noted that this flux is not a remnant wave train (which would appear as a peak at different times τ in the three pairs). It corresponds to the preferential direction of propagation of the diffuse field intensity. Using this array technique, we evaluated quantitatively the incident direction of the seismic anisotropic flux to be +22 • relatively to G4-G3 (Fig. 4), pointing in the S-E direction to Steno crater, as either a dense area of scatterers or an area with intense thermal moonquake activity.

We have presented a technique to investigate the subsurface between passive geophones based on the correlation of lunar seismic noise. We have shown that even in a quiet seismic environment with feeble sources, it is possible to obtain a Rayleigh wave dispersion curve. From the inversion of this dispersion curve we estimated the shear wave velocity profile, which provided new information on the velocity structure of the regolith at the Apollo 17 site. Moreover, we have established the Sun as an active generator of lunar seismic noise. In particular the SNR of the reconstructed Rayleigh pulse was found to be strongly dependent on solar illumination. The seismic activity originates from the strong thermal gradients induced during lunar day as well as night. We have applied an array technique for locating noise sources. The weak anisotropy of the seismic diffuse waves reveals a preferential direction of propagation, possibly originating from an area with dense scatterers or increased thermo-seismic activity.

The results presented here establish the method of extracting the Rayleigh-wave GF by cross-correlating seismic noise, as indeed extendable to extraterrestrial planets that not only differ in size, evolution and consequently seismic activity, but also in nature of origin of the noise from that of the Earth. This provides a novel avenue for future seismic exploration of the planets on which quakes might occur infrequently and are most probably also inhomogeneously distributed, of which Mars might be cited as an example [START_REF] Golombek | A prediction of Mars seismicity from surface faulting[END_REF]. In addition it holds the potential of increasing the scientific return, as noise between events can be successfully used rather than being discarded as has traditionally been the case. Specifically, to probe deeper into the subsurface on future seismic missions, the following points should be kept in mind. Distances between stations should preferably be between one and a few tens of wavelengths, as scattering attenuation might become important for greater distances. The depth probed being roughly 1/3 of the Rayleigh wavelength, this implies going to lower frequencies which necessitates the deployment of broadband seismometers [e.g. [START_REF] Lognonné | The Net-Lander very broad band seismometer[END_REF].

FIG. 1 :FIG. 2 :

 12 FIG.1: Configuration of the Apollo 17 LSPE experiment. It was composed of four geophones (velocimeters): G1, G2, G3 and G4, all connected to a central station for signal sampling, digitization and telemetering. A sample of raw seismic data from each geophone on Aug. 16, 1976 (UTC time) is displayed in the enclosed box (no logarithmic decompression). Typical correlations C13(τ ), C23(τ ), C34(τ ) are plotted between the corresponding pair of sensors. Crosses in the center of each correlation trace mark τ =0. NASA photo A17.S72 37259.

  FIG. 3: (a) Example of correlation C34(τ ) filtered in the 4-12 Hz range. The right peak (causal part, τ >0) corresponds to the Rayleigh wave propagating from G4 to G3 as if G4 was a vertical impulsive source. The left peak is the acausal part, τ <0. (b) SNR of the causal (right) and acausal (left) Rayleigh pulse as a function of record date d (x -axis in julian days from 1976 to 1977). Thick lines represent days when the Sun was shining and heating the Apollo 17 landing site. The increase in the SNR is synchronized with the Sun's illumination, oscillating with a periodicity of 29.5 days.

FIG. 4 :

 4 FIG. 4: Schematic view of the anisotropic flux.

Acknowledgments

The authors which to thank A. Paul and F. Touvenot for technical help, R. Weaver, N. Shapiro, L. Stehly, A. Derode and the LOA team for scientific advise. The CNRS GdR ImCODE has strongly encouraged this work. A. Khan acknowledges support from the Carlsberg Foundation, and Y. Nakamura from NASA grant NNG04GG62G.