Cafeteria-style feeding trials provide new insights into the diet and nutritional strategies of the black snub-nosed monkey (Rhinopithecus strykeri): Implications for conservation

Anthropogenic changes and fragmentation of natural habitats often exert a negative effect on resource availability and distribution, and the nutritional ecology and feeding behavior of nonhuman primates. The goals of this study are to examine food choice and to identify the nutritional profile of foods consumed by the Critically Endangered black snub-nosed monkey (Rhinopithecus strykeri). To accomplish our study goals, we presented cafeteria-style feeding trials of fresh food items collected in the home range of wild black snub-nosed monkeys to the only two captive R. strykeri, and compared the nutritional profiles of the leafy foods (buds, young, and mature leaves, 100 items from 70 plant species) selected with those avoided (54 items from 48 plant species). Overall, the results indicate that captive R. strykeri selected foods that were higher in moisture (Mo; 77.7%), crude protein (CP; 21.2%), total nonstructural carbohydrates (TNC; 34.9%), and phosphorus (P; 0.37%) while tending to avoid foods with a neutral detergent fiber (NDF) content of greater than 46.8%. Leaves collected in autumn and selected by the monkeys were characterized by a slightly higher amount of metabolizable energy (ME) than those rejected (1,350 kJ/100 g vs. 1,268 kJ/100 g). In contrast, the protein content of foods collected and consumed during the spring was greater (22.9%) than in autumn (16.4%). Random Forests modeling, an ensemble learning method, indicated that the proportion of Mo, NDF, ME, CP, P, and TNC were among the most important factors in predicting which items were consumed by the captive R. strykeri during spring and autumn. On the basis of the nutritional profile of foods consumed across the two seasons, we identified 18 nutrient-rich native plant species that we recommend for use in ex- and in-situ conservation management and reforestation programs to provide long-term access to a nutritionally adequate diet.     

Nutritional Ecology of <Emphasis Type="Italic">Ateles chamek</Emphasis> in lowland Bolivia: How Macronutrient Balancing Influences Food Choices

All free-living animals must make choices regarding which foods to eat, with the choices influencing their health and fitness. An important goal in nutritional ecology is therefore to understand what governs animals’ diet selection. Despite large variation in the availability of different food items, Peruvian spider monkeys (Ateles chamek) maintain a relatively stable daily protein intake, but allow total energy intake to vary as a function of the composition of available food items. This is referred to as protein-dominated macronutrient balancing. Here we assess the influence of this nutritional strategy on daily and seasonal nutritional intakes, estimate the nutritional value of different foods, and interpret unusual food choices. We conducted continuous all-day observations of focal spider monkeys inhabiting a semideciduous forest in Bolivia. We recorded feeding events, collected foods, and analyzed their nutrient content. By using the Geometric Framework for nutrition, we show that individuals reached their daily end-point in nutrient space —balance between protein and nonprotein energy intake— by consuming nutritionally balanced foods or by alternating between nutritionally complementary foods. The macronutritionally balanced figs of Ficus boliviana were their primary staple food and therefore dominated their overall nutritional intake. Our results also demonstrate that spider monkeys consumed a diverse array of ripe fruits to overcome periods of fig scarcity rather than vice versa; they could obtain sufficient protein on a diet of pure fruit; and unripe figs constituted a nutritionally rewarding and reliable food resource. We hope that the approaches taken and the conclusions reached in this study will catalyze further inquiries into the nutritional ecology of frugivorous primates.     

Use of wild and cultivated foods by chimpanzees at Bossou,Republic of Guinea: feeding dynamics in a human‐influenced environment

Increased human population growth and more conversions of natural habitat to agricultural land have resulted in greater proximity between humans and nonhuman primate species. Consequent increases in resource competition including crop‐raiding are a by‐product of both natural resources becoming less available and the nutritional benefits of cultivated foods becoming more known to the nonhuman primates. Chimpanzees at Bossou in the Republic of Guinea, West Africa, consume 17 different types of cultivated foods that are grown extensively throughout their small, fragmented home range. Direct observations of feeding behavior conducted over an 18‐month period revealed that during specific months crops account for up to one quarter of chimpanzee feeding time, with higher overall crop‐raiding levels throughout the periods of wild fruit scarcity. Some cultivated foods, especially sugar fruits, are mostly fallback foods, whereas others, such as rice pith (Oryza sp.) and maize (Zea mays), are consumed according to their availability even when wild foods are abundant. These findings highlight the importance of both crop choice by farmers and a thorough understanding of the ecology of resident primate species when establishing land management techniques for alleviating human–primate conflict. Am. J. Primatol. 71:636–646, 2009. © 2009 Wiley‐Liss, Inc.     

Effect of food preparation on feeding behavior of lion-tailed macaques

Ten group-living lion-tailed macaques (Macaca silenus), accustomed to receiving fruits and vegetable items of the diet in chopped form, were given these same foods in whole form to compare reactions to the non-nutritional properties of food. Contrary to common belief, the access of individuals to the different food items was not equalized through chopping into bite-sized morsels. Mean dietary diversity actually increased with presentation of whole foods, as did time spent feeding and total amount of food consumed. The widespread practice of chopping of food for captive primates has little to commend it in light of these findings.     

Enclosure environment affects the activity budgets of captive Japanese macaques (Macaca fuscata)

Individuals adapt to changes in their environment, such as food availability and temperature, by adjusting the amount of time spent in different behavioral activities. These adjustments in behavior should vary across age-sex class according to specific physiological and social needs. We studied the activity budgets of three social Japanese macaque groups inhabiting either vegetated or nonvegetated enclosures in order to compare the effects of access with vegetation, as both food and substrate on resting, feeding, grooming and moving activities over a 12-month period. Daily access to natural foods for monkeys in the vegetated enclosure seems to be largely responsible for the differences in daily time budgets of these three groups. Resting time in all three groups was longer than the time devoted to other activities. Resting and moving time in the two nonvegetated enclosures was significantly longer than in the vegetated enclosure. In contrast, feeding and grooming time was significantly longer in the vegetated enclosure. Seasonal variation in time spent feeding, resting and grooming was significantly effected by enclosure type. In all three enclosures, immatures, particularly females, spent more time feeding and moving, whereas adults spent more time resting. Significant monthly variation in time spent by age-sex class was noted only for feeding and resting. Interestingly, in the vegetated enclosure, time spent feeding on natural vegetation was equal to the amount of time spent feeding on provisioned food. This suggests that factors other than energetic and nutritional needs may be important determinants of the activity budget of the species. These results have important implications for the enrichment of captive primates and our understanding of the maintenance of activity patterns by primates in the wild.     

Foraging behaviour of the Brazilian squirrelSciurus aestuans (Rodentia, Sciuridae)

We describe the foraging behaviour of the Brazilian squirrelSciurus aestuans Linnaeus, 1776 in a natural free-living population, in an area with a high concentration of palm fruitsSyagrus romanzoffiana (Chamisso) Glassman. Our objective was to investigate if the abundance ofS. romanzoffiana fruits, an important food item for squirrels, temporally influenced the foraging behaviour of this population. The observations were carried out over an eight-month (April–November 2001) period. Fruiting phenology ofS. romanzoffiana was also monitored. The most consumed food item for this period was the fruit ofS. romanzoffiana (70%), followed by foods of human origin (14%). The percentage of time spent feeding increased in September, and the time spent travelling declined in September, October and November, when females were observed showing evidence of reproductive activity. At the same timeS. romanzoffiana fruits become available. The consumption of human items illustrates the opportunistic feeding habit of these squirrels, but variations in foraging behaviour detected probably were more strongly related to availability ofS. romanzoffiana fruits.     

Forest fragments become farmland: Dietary Response of wild chimpanzees (Pan troglodytes) to fast-changing anthropogenic landscapes

Behavioral flexibility, including an ability to modify feeding behavior, is a key trait enabling primates to survive in forest fragments. In human-dominated landscapes, unprotected forest fragments can become progressively degraded, and may be cleared entirely, challenging the capacity of primates to adjust to the changes. We examined responses of wild chimpanzees (Pan troglodytes schweinfurthii) to major habitat change: that is, clearance of forest fragments for agriculture. Over 7 years, fragments in Bulindi, Uganda, were reduced in size by 80%. We compared the chimpanzees’ diet at the start and end of this period of rapid deforestation, using data derived mainly from fecal analysis. Similar to other long-term study populations, chimpanzees in Bulindi have a diverse diet comprising over 169 plant foods. However, extensive deforestation seemed to impact their feeding ecology. Dietary changes after fragment clearance included reduced overall frugivory, reduced intake of figs (Ficus spp.; formerly a dietary “staple” for these chimpanzees), and reduced variety of fruits in fecal samples. Nevertheless, the magnitude of most changes was remarkably minor given the extent of forest loss. Agricultural fruits increased in dietary importance, with crops accounting for a greater proportion of fruits in fecal samples after deforestation. In particular, cultivated jackfruit (Artocarpus heterophyllus) became a “staple” food for the chimpanzees but was scarcely eaten before fragment clearance. Crops offer some nutritional benefits for primates, being high in carbohydrate energy and low in hard-to-digest fiber. Thus, crop feeding may have offset foraging costs associated with loss of wild foods and reduced overall frugivory for the chimpanzees. The adaptability of many primates offers hope for their conservation in fragmented, rural landscapes. However, long-term data are needed to establish whether potential benefits (i.e. energetic, reproductive) of foraging in agricultural matrix habitats outweigh fitness costs from anthropogenic mortality risk for chimpanzees and other adaptable primates.     

Feeding ecology and activity pattern of black-fronted titi monkeys (<Emphasis Type="Italic">Callicebus nigrifrons</Emphasis>) in a semideciduous tropical forest of southern Brazil

Most aspects of the ecology and behavior of Callicebus nigrifrons are still unknown. The information available about this species is mainly based on a few studies that also focused on other Callicebus. We examined the feeding behavior and activity pattern of a free-ranging pair of C. nigrifrons between March and November 2007 in an area of semideciduous tropical forest of southeastern Brazil. The study site is located at the southern limit of the Tropical Zone and is characterized by pronounced seasonality. As observed for other Callicebus monkeys, fruits were the most consumed food resource, accounting for 53% of the diet, which was complemented mainly by leaves (16%) but also by invertebrates and flowers (10% of each). A great variety of plant families (28) and species (62) were included in the diet. The titis spent 35% of their time feeding, distributing the remaining time between resting (30%) and traveling (24%). Data presented here indicate that C. nigrifrons prefer high-quality food items (fruit pulp), adding low-quality food items (such as leaves) as the availability of the higher-quality foods decreases. The amount of time spent traveling and resting did not change between seasons, but the time invested in feeding increased during the lean period. The activity pattern was not related to fruit availability, but in months with lower temperatures, monkeys spent more time feeding. We suggest that the feeding ecology and activity pattern of C. nigrifrons reflect adaptations related to annual fluctuations in food availability and temperature, respectively.     

Climatic determinants of diet and foraging behaviour in baboons

Baboons (Papio spp.) are characterised by a large degree of variation in foraging behaviour and dietary composition. Previous analyses have suggested that much of this can be traced to differences in ecological conditions between sites. The proximate mechanism underlying these relationships is assumed to be mediated via the impact of climatic conditions on food availability, and ultimately the impact that this has on dietary composition. This paper examines these relationships more explicitly. Data from 15 baboon populations were used to assess the relationship between foraging variables and dietary composition. Only feeding time showed significant relationships with dietary composition, with percentage of time spent feeding decreasing with proportion of fruit in the diet, and increasing with the proportion of subterranean items. No relationships were found between diet composition and moving time or day journey length, although significant relationships were found between these variables and group size. The proportions of feeding time spent feeding on fruit, subterranean items and leaves were functions of the ecological conditions experienced by that population, although no relationships were found for the percentage of feeding time devoted to flowers or animal material. The relationships between the proportion feeding time spent on fruits, leaves and subterranean items and ecological variables could be best explained through understanding the way in which bush and tree level vegetation respond to the climatic environment and the impact this has on fruit availability. In this respect, temperature and seasonality are the key climatic parameters. This provides good support for the idea that the proximate mechanism underlying the relationship between foraging time and ecological variables is mediated via the impact of the climatic environment on vegetation structure and food availability. Similar factors have been proposed to explain much of the geographic variation in species diversity, suggesting that these relationships have far wider relevance and may account for much of the observed geographical variation in mammalian behaviour.     

Influence of Human Food Consumption on the Time Budget of Vervets

In nonhuman primate groups that utilize crop and food-raiding strategies, the inclusion of human food in the diet can have a pervasive impact on the activity budget. Human food is usually of higher quality and energy per unit than wild food. Thus, metabolic demands may be reached sooner on a human food diet, which in turn leads to improved foraging efficiency. In particular, a reduction in time spent feeding is associated with an increase in time spent resting. We investigated changes in time budget in a group of vervets (Chlorocebus aethiops pygerthrus) living in a tourist and cultivated area of Entebbe, Uganda (Zoo group). Saj collected 123 hr of focal observations on 17 individuals. Human food constituted half of the diet of Zoo group. Access to human food resulted in a high proportion of time resting and a low proportion of time feeding. The group had a small average daily range and a small home range in relation to other reports on unprovisioned groups. The time budget differences suggest that the juveniles spent more time moving and feeding and less time resting than adults did, and that adult females were more social than adult males were. These patterns have been observed in both provisioned and unprovisioned vervet groups. In contrast to a report from an unprovisioned group (Harrison, 1983), lactating females in this provisioned situation were able to maintain feeding and activity levels similar to those of other adults. However, adult females spent significantly less time consuming human food than juveniles did. We suggest that the risk associated with human food consumption may explain the low consumption of human food by females with dependent offspring. The differences may also reflect the different nutritional requirements of lactating females or the tendency for juveniles to be more exploratory than other group members.     

Fallback Foods of Red Leaf Monkeys (Presbytis rubicunda) in Danum Valley, Borneo

Animals in Southeast Asia must cope with long periods of fruit scarcity of unpredictable duration between irregular mast fruiting events. Long-term data are necessary to examine the effect of mast fruiting on diet, and particularly on the selection of fallback foods during periods of fruit scarcity. No such data is available for colobine monkeys, which may consume substantial amounts of fruits and seeds when available. We studied the diet of red leaf monkeys (Presbytis rubicunda, Colobinae) in Danum Valley, Sabah, northern Borneo, using 25 mo of behavioral observation, phenology and vegetation surveys, and chemical analysis to compare leaves eaten with nonfood leaves. The monkeys spent 46% of their feeding time on young leaves, 38% on seeds, 12% on whole fruits, 2.0% on flowers, 1.0% on bark, and 1.2% on pith. They spent more time feeding on seeds and whole fruit when fruit availability was high and fed on young leaves of Spatholobus macropterus (liana, Leguminosae) as fallback foods. This species was by far the most important food, constituting 27.9% of the total feeding time, and the feeding time on this species negatively correlated with fruit availability. Consumed leaves contained more protein than nonconsumed leaves, and variation in time spent feeding on different leaves was explained by their abundance. These results suggest that red leaf monkeys show essentially the same response to the supra-annual increase in fruit availability as sympatric monogastric primates, increasing their seed and whole-fruit consumption. However, they depended more on young leaves, in particular Spatholobus macropterus, as fallback foods during fruit-scarce periods than did gibbons or orangutans. Their selection of fallback food appeared to be due to both nutrition and abundance.     

Nutrient contents predict the bamboo‐leaf‐based diet of Assamese macaques living in limestone forests of southwest Guangxi,China

Determining the nutrient factors influencing food choice provides important insight into the feeding strategy of animals, which is crucial for understanding their behavioral response to environmental changes. A bamboo‐leaf‐based diet is rare among mammals. Animals’ food choice and nutritional goals have been explained by several frameworks; however, the influence of nutrients on food choice in bamboo‐leaf‐based macaques is not yet available. Assamese macaques (Macaca assamensis) inhabiting limestone forests are characterized by such a bamboo‐leaf‐based diet, predominantly consuming young leaves of Bonia saxatilis, a shrubby, karst‐endemic bamboo. We studied the feeding behavior of one group of Assamese macaques using instantaneous scan sampling in limestone forests of the Guangxi Nonggang National Nature Reserve in southwest Guangxi, China. We compared the nutrient content of staple food and nonfood items and examine the role of key nutrients in the food selection of macaques. Our results showed that young leaves of bamboo B. saxatilis contained more water, crude protein, phosphorus, and less tannin than nonfood items. Furthermore, staple foods contained a higher content of water and less content of calcium than nonfood items. More specifically, quantities of water, crude protein, calcium, and phosphorus in food items were critical factors affecting feeding time on a specific plant item. Our results suggest that young bamboo leaves could meet macaques’ required protein and water intake, while enabling them to maintain their mineral balance, consequently facilitating to maintain the primates’ bamboo‐leaf‐diet in the limestone forest. Our findings confirm the effects of nutrient contents in food choice of Assamese macaques, highlighting the importance of the nutrient contents in maintaining their bamboo‐based diet and the need to increase the knowledge on their nutritional strategy adapted to the bamboo‐dominated diet inhabiting the unique limestone habitat.     

The macronutrient composition of wild and cultivated plant foods of West African chimpanzees (Pan troglodytes verus) inhabiting an anthropogenic landscape

Agricultural expansion encroaches on tropical forests and primates in such landscapes frequently incorporate crops into their diet. Understanding the nutritional drivers behind crop-foraging can help inform conservation efforts to improve human-primate coexistence. This study builds on existing knowledge of primate diets in anthropogenic landscapes by estimating the macronutrient content of 24 wild and 11 cultivated foods (90.5% of food intake) consumed by chimpanzees (Pan troglodytes verus) at Bossou, Guinea, West Africa. We also compared the macronutrient composition of Bossou crops to published macronutrient measures of crops from Bulindi, Uganda, East Africa. The composition of wild fruits, leaves, and pith were consistent with previous reports for primate diets. Cultivated fruits were higher in carbohydrates and lower in insoluble fiber than wild fruits, while wild fruits were higher in protein. Macronutrient content of cultivated pith fell within the ranges of consumed wild pith. Oil palm food parts were relatively rich in carbohydrates, protein, lipids, and/or fermentable fiber, adding support for the nutritional importance of the oil palm for West African chimpanzees. We found no differences in the composition of cultivated fruits between Bossou and Bulindi, suggesting that macronutrient content alone does not explain differences in crop selection. Our results build on the current understanding of chimpanzee feeding ecology within forest-agricultural mosaics and provide additional support for the assumption that crops offer primates energetic benefits over wild foods.     

Flowers Are an important food for small apes in southern Sumatra

Flowers are included in the diets of many primates, but are not generally regarded as making an important contribution to primate energy budgets. However, observations of a number of lemur, platyrrhine, and cercopithecine populations suggest that some flower species may function as key primate fallback foods in periods of low abundance of preferred foods (generally ripe fruits), and that flowers may be preferred foods in some cases. I report heavy reliance on flowers during some study months for a siamang (Symphalangus syndactylus) population in southern Sumatra. Siamangs at Way Canguk spent 12% of feeding time eating flowers from October 2000 to August 2002, and in 1 month flower‐feeding time exceeded 40% of total feeding time. The overall availabilities of fig and nonfig fruits, flowers, and new leaves in the study area were not significant predictors of the proportion of time that siamangs spent consuming any plant part. However, flower‐feeding time was highest in months when nonfig fruit‐feeding time was lowest, and a switch from heavy reliance on fruit to substantial flower consumption was associated with a shift in activity patterns toward reduced energy expenditure, which is consistent with the interpretation that flowers may function as a fallback food for Way Canguk siamangs. Hydnocarpus gracilis, a plant from which siamangs only consume flowers, was the third‐most‐commonly consumed plant at Way Canguk (after Ficus spp. and Dracontomelon dao), and flowers from this plant were available in most months. It is possible that relatively high local availability of these important siamang plant foods is one factor promoting high siamang density in the study area. Am. J. Primatol. 71:624–635, 2009. © 2009 Wiley‐Liss, Inc.     

Environmental influences on mountain gorilla time budgets

Data on the time budgets of mountain gorillas (Gorilla gorilla beringei) were collected during field studies in the Virunga Volcanoes region of Rwanda and Zaire. Focal sampling was used to determine the proportion of time that individuals of different age/sex classes spent in several mutually exclusive activity states. The gorillas spent the majority of daylight hours feeding; most of the rest of the day was devoted to resting, with little time spent moving or engaged in social activity. The time budget varied among the different subhabitats used by the gorillas, and the gorillas satisfied subsistence needs more quickly when in areas where food was more abundant and/or of better nutritional quality. Silverbacks spent more time feeding than all other age/sex classes, but age/sex class differences were not great. All age/sex classes responded to variability in habitat quality in similar fashion. Unlike the case for many other primates, there was no significant seasonal variation in time budgets. There was a direct relationship between group size and time spent feeding, although variation in relation to group size was lower than that in relation to variation in habitat quality. These results are consistent with the relationship of feeding time to body size in primates. They are also consistent, with other evidence that social foraging entails a cost to gorilla females, but that this cost is low in comparison to those faced by many other primates. Permanent association with males apparently offers little ecological disadvantage to females, who are likely to be more than compensated by mutualistic benefits.     

Graminivory and Fallback Foods: Annual Diet Profile of Geladas (<Emphasis Type="Italic">Theropithecus gelada</Emphasis>) Living in the Simien Mountains National Park,Ethiopia

All primates show some dietary flexibility, particularly during food shortages. Foods consumed during times of scarcity (i.e., fallback foods) strongly influence the ecology and evolution of a species. Geladas (Theropithecus gelada) eat primarily graminoid leaves (i.e., grasses and sedges), but also consume other diet items (e.g., underground storage organs), especially in the dry season. We investigated the feeding ecology of wild geladas in the Sankaber region of the Simien Mountains National Park, Ethiopia across 12 mo. We asked how the gelada diet in this region, which is disturbed by livestock and agriculture, correlated with food availability and whether underground foods are fallback foods. We quantified the monthly diets of adults from eight reproductive units using instantaneous scan sampling, and seasonal aboveground and underground food availability using point-intercept transects and soil core sampling. Geladas primarily consumed graminoid leaves year-round (76.3% of the annual diet, 36.2–93.2% of the monthly diet) but spent considerable time consuming underground foods in the dry season (14.0% of the annual diet, 11.1–49.7% of the diet across dry season months). Graminoid consumption increased with graminoid availability, and underground food consumption decreased with graminoid availability. Underground food availability did not vary significantly between the dry and wet season sampling months, supporting the hypothesis that underground foods are fallback foods for geladas. We then compiled data from gelada feeding studies and found that underground foods are an important dry season diet item across study sites, but geladas rely more heavily on underground foods in habitats more heavily influenced by humans. Understanding the range and effects of primate dietary flexibility in human-modified habitats will contribute to a better understanding of how changing environments shape primate ecology and evolution.     

The Hand That Feeds the Monkey: Mutual Influence of Humans and Rhesus Macaques (<Emphasis Type="Italic">Macaca mulatta</Emphasis>) in the Context of Provisioning

Historically, humans and other primates (primates henceforth) have coexisted across cultures and contexts, and many primate populations use anthropogenic food sources as their main or supplementary food. While primates may actively forage for such food, they are also directly provisioned by humans in many regions. Ethnoprimatology views humans and primates as cohabitants of integrated socioecological spaces who mutually influence each other’s ecologies and social lives. We contextualized provisioning of primates by humans within an ethnoprimatological framework and examined if the availability of anthropogenic food affected primate diets or the amount of time primates spent in anthropogenic habitats and whether primates influenced the human act of provisioning. To this end, we used scan sampling on a group of rhesus macaques across a year, and conducted interviews with 86 people who paused at a nearby tea shop for refreshments. We found that the macaques’ consumption of natural resources and dietary diversity decreased, and they spent more time in human-modified habitats when provisioned food was available. We also found that particular behaviors of the provisioned macaques stimulated provisioning by humans. Our findings show that provisioning influences macaque feeding ecology and habitat use, and that the behavior of the macaques themselves drives people to provide them with food subsidies, illustrating a complex web of interactions between the sympatric species.     

Seasonal Energetic Stress in a Tropical Forest Primate: Proximate Causes and Evolutionary Implications

Animals facing seasonal variation in food availability experience selective pressures that favor behavioral adjustments such as migration, changes in activity, or shifts in diet. Eclectic omnivores such as many primates can process low-quality fallback food when preferred food is unavailable. Such dietary flexibility, however, may be insufficient to eliminate constraints on reproduction even for species that live in relatively permissive environments, such as moist tropical forests. Focusing on a forest-dwelling primate with a flexible diet (Cercopithecus mitis) we investigated whether females experience seasonal energetic stress and how it may relate to reproductive seasonality. We used fecal glucocorticoids (fGCs) as an indicator of energetic stress, controlling for the potentially confounding effects of social interactions and reproductive state. We modeled within-female fGC variation with General Linear Mixed Models, evaluating changes in feeding behavior and food availability as main effects. Regardless of reproductive state, fGCs increased when females shifted their diet towards fallback foods (mature leaves and other non-preferred items) and when they spent more time feeding, while fGCs decreased with feeding time on preferred items (insects, fruits, young leaves) and with the availability of young leaves. Changes in fruit availability had no general effects on fGCs, likely because fruits were sought out regardless of availability. As predicted, females in the energetically demanding stages of late pregnancy and early lactation showed greater increases in fGCs between periods of low versus high availability of fruits and young leaves than females in other reproductive states. Potential social stressors had no measurable effects on fGCs. Preliminary evidence suggests that seasonal energetic stress may affect the timing of infant independence from mothers and contribute to unusually long inter-birth intervals compared to closely related species of similar body size. Our findings highlight how the study of stress responses can provide insights into the proximate control of reproductive strategies.     

Seasonal Variation in the Activity Patterns and Time Budgets of <Emphasis Type="Italic">Trachypithecus francoisi</Emphasis> in the Nonggang Nature Reserve,China

Activity patterns and time budgets are 2 important aspects of animal behavior that researchers use to investigate ecological influences on individual behavior. We collected data on activity patterns and time budgets in 1 group of François’ langurs (Trachypithecus francoisi) from August 2003 to July 2004 in the Nonggang Nature Reserve, Guangxi Province, China, via instantaneous scan sampling method with 15-min intervals. The diurnal activity pattern of François’ langurs showed morning and afternoon feeding peaks, with a midday resting peak. Seasonal change was apparent in the activity pattern: 2 significant feeding peaks occurred in the dry season and only 1 significant feeding peak in the rainy season. The group spent an average of 51.5% of the daytime resting. Feeding and moving accounted on average for 23.1% and 17.3% of the activity budget, respectively. Subjects spent little time on social activities, averaging 2% for grooming and 5.5% for playing. Their time budgets showed significant seasonal variation: they spent a greater proportion of time on feeding and less time on resting and grooming in the dry season than in the rainy season. They also differed among different sex-age classes: immatures spent more time playing, whereas adults devoted more time to resting, feeding, and grooming. Correlations between time budgets and food items or food availability clearly indicated that François’ langurs might adopt an energy-maximizing strategy when preferred foods were scarce in the dry season.     

Seasonal and individual predictors of diet in a free‐ranging population of mandrills

Deciphering the dietary habits of a species is central to understanding its ecology, resource requirements, and the evolution of its life history traits. Detailed information on how primates use their environment to address their nutritional needs is available for many primate species. Such basic, but necessary data are, however, fragmented for secretive primates, especially regarding direct behavioral observations of individuals. In this study, we evaluated the impact of seasonality and demographic characteristics on diet and feeding habits in the only free‐ranging population of habituated mandrills (Mandrillus sphinx), a forest‐dwelling species inhabiting the dense humid forests of Central Africa. We collected fine‐grained quantitative data on feeding behavior of 57 individually‐recognized animals of both sexes and different age classes during a 17‐month period. We identified most consumed plant species and determined their abundance in the habitat of the studied mandrills. We showed that diet in this species was extremely diverse and included approximately 150 different plant species, but also mushrooms, invertebrates, and vertebrates. This omnivorous and highly diverse diet presented, however, a clear frugivorous tendency. While we identified three food items largely consumed throughout the year, we also found a strong seasonal signature on diet that was partly, but not only, related to food availability. Age and sex also influenced feeding habits with some feeding specializations according to the individual categories considered and their associated nutritional needs. Our quantitative data provide a basis for future studies examining the nutritional and mineral content of food items, which will further elucidate important aspects of the ecology of this little studied forest primate.