Periods Of Low Fruit Availability Research Articles

Predictors of respiratory illness in western lowland gorillas.

Infectious disease is hypothesized to be one of the most important causes of morbidity and mortality in wild great apes. Specific socioecological factors have been shown to influence incidences of respiratory illness and disease prevalence in some primate populations. In this study, we evaluated potential predictors (including age, sex, group size, fruit availability, and rainfall) of respiratory illness across three western lowland gorilla groups in the Republic of Congo. A total of 19,319 observational health assessments were conducted during daily follows of habituated gorillas in the Goualougo and Djéké Triangles over a 4-year study period. We detected 1146 incidences of clinical respiratory signs, which indicated the timing of probable disease outbreaks within and between groups. Overall, we found that males were more likely to exhibit signs than females, and increasing age resulted in a higher likelihood of respiratory signs. Silverback males showed the highest average monthly prevalence of coughs and sneezes (Goualougo: silverback Loya, 9.35 signs/month; Djéké: silverback Buka, 2.65 signs/month; silverback Kingo,1.88 signs/month) in each of their groups. Periods of low fruit availability were associated with an increased likelihood of respiratory signs. The global pandemic has increased awareness about the importance of continuous monitoring and preparedness for infectious disease outbreaks, which are also known to threaten wild ape populations. In addition to the strict implementation of disease prevention protocols at field sites focused on great apes, there is a need for heightened vigilance and systematic monitoring across sites to protect both wildlife and human populations.

After the smoke has cleared: Extended low fruit productivity following forest fires decreased gregariousness and social tolerance among wild female Bornean orangutans (Pongo pygmaeus wurmbii)

As climate change continues to fundamentally alter resource landscapes, the ability to flexibly respond to spatio-temporal changes in the distribution of preferred food sources is increasingly important for the overall health and fitness of animals living in seasonal, variable, and/or changing environments. Here, we investigate the effects of an uncharacteristically long period of fruit scarcity, following widespread thick haze caused by peat and forest fires in 2015, on the behaviour and sociality of female Bornean orangutans (Pongo pygmaeus wurmbii). We collected data from 2010 to 2018 at Tuanan, Central Kalimantan, Indonesia, and compared the activity, diet, and association patterns of adult females during low-fruit periods before the fires, i.e., regular, seasonal periods of low fruit availability (“pre-fire”), and after the fires, i.e., during the extended period of low fruit availability (“post-fire”). First, we found that, post-fire, female orangutans adopted a more extreme energy-saving activity pattern and diet — resting more, travelling less, and diet-switching to less-preferred foods — compared to pre-fire. Second, we found that the probabilities of association between females and their weaned immature offspring, and between related and unrelated adult females were lower, and the probability of agonism between unrelated females was higher, post-fire than pre-fire. This change in energetic strategy, and the general reduction in gregariousness and social tolerance, demonstrates how forest fires can have lasting consequences for orangutans. Fission–fusion species such as orangutans can mitigate the effects of changes in resource landscapes by altering their (sub)grouping patterns; however, this may have long-term indirect consequences on their fitness.

Does spatial and seasonal variability in fleshy-fruited trees affect fruit availability? A case study in gallery forests of Central Brazil

Forest stands in seasonal environments can differ spatially and seasonally in the diversity of fleshy fruits available as resources for fauna. The aim of this study was to quantify spatial and seasonal variation in the richness and abundance of the dominant fleshy-fruited tree species in gallery forests of the Cerrado domain. Tree species composition and abundance were compiled from the literature for 10 gallery forest stands. Data were interpolated and extrapolated by the sample coverage method, using Hill numbers to determine the typical species as well as the most abundant species in each fruiting season. Stands differed in the occurrence of fleshy-fruited tree species and in the number of fleshy-fruited tree individuals. Probabilities for the occurrence of fleshy fruit were similar between in the wet and dry. However, across all stands, species that fruit primarily in the dry season were less common than those that fruit in the wet season. The sharing of fleshy-fruited tree species was low and the most abundant species differed among the studied stands. Fleshy fruits were available all year round and periods of high fruit availability are highly synchronized while periods of low fruit availability were much less so.

Chimpanzee ranging responses to fruit availability in a high-elevation environment.

Most primates experience seasonal fluctuations in the availability of food resources and face the challenge of balancing energy expenditure with energy gain during periods of resource scarcity. This is likely to be particularly challenging in rugged, montane environments, where available energy is relatively low and travel costs are high. Chimpanzees (Pan troglodytes) show extensive behavioral diversity across study sites. Yet, as most research has focused on low- and mid-elevation sites, little is known on how chimpanzees respond to periods of low fruit availability in harsh montane environments. We use focal follow and phenology data to investigate how fruit availability influences daily path length and monthly home range in chimpanzees living in Nyungwe National Park, a montane forest in Rwanda. Nyungwe chimpanzees decreased their daily travel distances during periods of fruit scarcity. However, this decrease in travel effort did not correspond with a decrease in foraging area. Instead, monthly homes ranges shifted location across the study period. Nyungwe chimpanzees occupy a relatively wide altitudinal range and the shifts in monthly home range location may reflect differences in the altitudinal distribution of food resources. Chimpanzee monthly diet was often dominated by one or two species and each of these species were confined to different elevation zones. One important species, Podocarpus latifolius, grew only at high elevations (2,600-2,950 m) and chimpanzees ranged at the altitudinal peak of their range for 2 consecutive months while feeding on this species. Thus, while high elevations are often thought to be harsh environments for primates, they can be an important part of a species' home range when they provide a refugium for densely distributed, important food species.

Duplication and parallel evolution of the pancreatic ribonuclease gene (RNASE1) in folivorous non-colobine primates, the howler monkeys (Alouatta spp.)

In foregut-fermenting mammals (e.g., colobine monkeys, artiodactyl ruminants) the enzymes pancreatic ribonuclease (RNASE1) and lysozyme C (LYZ), originally involved in immune defense, have evolved new digestive functions. Howler monkeys are folivorous non-colobine primates that lack the multi-chambered stomachs of colobines and instead digest leaves using fermentation in the caeco-colic region. We present data on the RNASE1 and LYZ genes of four species of howler monkey (Alouatta spp.). We find that howler monkey LYZ is conserved and does not share the substitutions found in colobine and cow sequences, whereas RNASE1 was duplicated in the common ancestor of A. palliata, A. seniculus, A. sara, and A. pigra. While the parent gene (RNASE1) is conserved, the daughter gene (RNASE1B) has multiple amino acid substitutions that are parallel to those found in RNASE1B genes of colobines. The duplicated RNase in Alouatta has biochemical changes similar to those in colobines, suggesting a novel, possibly digestive function. These findings suggest that pancreatic ribonuclease has, in parallel, evolved a new role for digesting the products of microbial fermentation in both foregut- and hindgut-fermenting folivorous primates. This may be a vital digestive enzyme adaptation allowing howler monkeys to survive on leaves during periods of low fruit availability.

Travel fosters tool use in wild chimpanzees.

Ecological variation influences the appearance and maintenance of tool use in animals, either due to necessity or opportunity, but little is known about the relative importance of these two factors. Here, we combined long-term behavioural data on feeding and travelling with six years of field experiments in a wild chimpanzee community. In the experiments, subjects engaged with natural logs, which contained energetically valuable honey that was only accessible through tool use. Engagement with the experiment was highest after periods of low fruit availability involving more travel between food patches, while instances of actual tool-using were significantly influenced by prior travel effort only. Additionally, combining data from the main chimpanzee study communities across Africa supported this result, insofar as groups with larger travel efforts had larger tool repertoires. Travel thus appears to foster tool use in wild chimpanzees and may also have been a driving force in early hominin technological evolution.

Effects of food availability and climate on activity patterns of western black-crested gibbons in an isolated forest fragment in southern Yunnan, China.

The critically endangered western black-crested gibbon (Nomascus concolor) is distributed in isolated habitat fragments in northern Vietnam, northwestern Laos, and southwestern China. To assess the behavioral adaptation of this species to forest fragments and its response to seasonal variation in food availability and climate, we present activity patterns of a group inhabiting an isolated forest based on two year-long studies in southern Yunnan, China. Annually, the gibbons spent nearly half of their active time resting, followed by moving and feeding. In both study periods, the time allocated to activities varied significantly between months, and was affected by food availability and climate factors. The group delayed retirement when tree fruit was abundant, and they decreased time spent moving and playing during periods of low fruit availability. In the cold months, the gibbons decreased time spent moving, and they decreased active time and resting time when rainfall was high. The results suggest that the group may seek to maximize net energy intake like energy maximizers when high quality food is most available, and adopt an energy-conserving strategy during periods of lower food availability and temperature. The gibbons showed similar diurnal variation in activity patterns to a group inhabiting a continuous forest at Dazhaizi, Mt. Wuliang, central Yunnan. However, they had a longer active period, and devoted more time to resting but less time to feeding. The individuals also spent lower percentages of time engaged in social behavior than those at Dazhaizi. These differences may be due to their smaller home range and unusual group composition caused by habitat fragmentation.

A Noninvasive Method for Estimating Nitrogen Balance in Free-Ranging Primates

The vital role of body protein as an energy reserve has received little focus in studies of wild primates. Owing to the relatively low protein content of fruit, some frugivorous primates could face a protein deficit if body protein is catabolized for energy during periods of low fruit availability. Such an imbalance can be detected if fatty acids, amino acids, and nitrogen (N) catabolites are reincorporated or recycled back to tissues. Here we describe a method to quantify protein recycling by measuring standardized urea concentration and N isotope signatures from urine samples collected from wild Bornean orangutans (Pongo pygmaeus wurmbii). Our overall goal was to explore if concentrations of urea and δ15N values could be used as indicators of the amount of protein consumed and the degree of protein recycling, respectively, in wild, free-ranging primates. We examine the relationships between urea concentration, δ15N values, protein intake, and fruit availability. Urea concentration increased with fruit availability, reflecting a slight increase in protein consumption when fruit was abundant. However, we found no relationship between δ15N values and fruit availability, suggesting that orangutans avert a negative protein balance during periods of low fruit availability. These noninvasive methods complement recent advances in primate energy balance research and will contribute to our understanding of adaptations of primates during periods of fruit shortage.

Social behavior, foraging strategies, and fecal glucocorticoids in female blue monkeys (Cercopithecus mitis): potential fitness benefits of high rank in a forest guenon

Socioecological theory predicts that aggressive feeding competition is associated with linear dominance hierarchies and reproductive advantages for high-ranking females. Female blue monkeys contest fruits and have a linear dominance hierarchy, yet previous research has shown no evidence that high-ranking females benefit from greater feeding success or fertility. Here, we assess whether individuals differ in fecal glucocorticoid (fGC) excretion and examine proximate determinants of such differences to infer potential fitness correlates of rank, using data collected from two study groups in the Kakamega Forest, Kenya. We found that higher ranking females had preferential access to fruits in both groups, although the behavioral mechanisms leading to this effect varied between groups. Despite a consistent rank difference in feeding on fruits, an overall rank effect on fGCs emerged in only one group; females of this group spent comparatively more time feeding on fruits, fruits accounted for a greater proportion of the diet, and females engaged in more frequent food-related agonism. In addition, more females in this group were lactating during a period of low fruit availability, when rank effects on fGCs were particularly strong. Regardless of fruit availability, among lactating females of both groups higher rank was associated with lower fGC levels, indicating lower energetic stress in higher ranking females when energy demands were particularly high. Individual rates of agonism, a potential psychological stressor, were unrelated to fGCs at all times. After we accounted for rates of agonism and feeding on fruits, females of one group who groomed others more had lower fGCs, suggesting that variable social coping behavior can contribute to fGC variation in some groups. This study provides the first empirical evidence that high-ranking female blue monkeys may obtain fitness benefits from their social status, by gaining priority of access to fruits during critical times in the reproductive cycle.

Food choices of the mountain gorilla in Bwindi Impenetrable National Park, Uganda: the influence of nutrients, phenolics and availability

Abstract:The factors that influence food choice have implications for animal survival, reproduction and population growth. We conducted a 1-y study of food choice by four mountain gorilla groups that consumed herbs and fruit at two locations differing spatially and temporally in food availability in Bwindi Impenetrable National Park, Uganda. We collected data on 45 important foods consumed by the gorillas, the availability of those foods in each gorilla group's home range and their corresponding nutrient and phenolic concentrations. Employing a linear multiple regression, we tested three hypotheses regarding the influence of food availability and the nutritional and phenolic concentrations of food on food choice. Regardless of changes in herb availability, the choice of herbs was positively influenced by their abundance and sugar concentrations and negatively influenced by their fibre, condensed tannin and protein concentrations. Furthermore, regardless of changes in fruit availability, the choice of fruit was positively influenced by its abundance and negatively influenced by its condensed tannin concentrations. During periods of low fruit availability, the gorillas did not increase the consumption of herbs high in fibre and sugar. The choice of herbs low in fibre had less of an influence on food choice at the location with lower fruit availability than the other location. Our results underscore the importance of incorporating both availability and nutrient concentrations into studies of food choice; by doing so we found Bwindi gorillas were able to choose abundant, relatively high-quality foods year round.

Fruiting phenology of palms and trees in an Atlantic rainforest land-bridge island

Tropical forests show periods of scarcity and high fruit production in the same year and/or between years. Palms are an important component of Neotropical rainforests and a significant food resource for several frugivores. Therefore, their role as keystone resource may be exacerbated in highly impoverished areas. In Anchieta Island, São Paulo/Brazil, human settlements have modified and impoverished the forest, mainly through overharvesting and the introduction of exotic plants and several mammal species. We assessed the offer of fruits consumed by vertebrate frugivores at this island, the vegetation of which is belonging to the Brazilian Atlantic rainforest. We compared whether the fruiting patterns and fruit fall differ between palms and trees, and discuss the importance of palms as a food resource for frugivores and the implications for Anchieta Island conservation. Phenological patterns were seasonal for both trees and palms; however, the times of fruiting occurrence differed. Fruit fall biomass was at least twice lower than reported for other Atlantic rain forests and was also different between trees and palms. Palms contributed more than 80% of the overall fruit fall biomass. Palms may constitute an alternative food resource in periods of low fruit availability, although they do not provide resources for the entire assemblage of vertebrate frugivores. Energy-rich fruits, such as those produced by palms, may play an important role in the maintenance of frugivore populations in isolated, disturbed environments with a high density of vertebrate frugivores, low diversity of fruiting species and fruit biomass such as those found on Anchieta Island.

Diet of the Cauca Guan: Exploitation of a Novel Food Source in Times of Scarcity

AbstractAlthough exotic species may have a negative impact on native organisms, they can in some cases provide abundant resources. Use of these resources may have important implications for habitat use, movement, and space requirements of native animals, and ultimately for population dynamics. We describe the diet of a population of the narrowly endemic Cauca Guan (Penelope perspicax) in the Colombian Andes. This guan demonstrates plasticity in its eating habits, feeding on an exotic tree species during periods of food scarcity. Based on direct observations and analysis of fecal samples over a one-year cycle, we found that guans fed on 89 species of fruits but also included foliage, flowers, and invertebrates in their diets. Guans fed on fruit species in proportion to their availability but favored some species with high fruit production or prolonged fruiting. Fruit availability, measured both in numbers of species and biomass, varied throughout the year, with a low in September–December. During the period of low fruit availability, guans congregated in large numbers at a Chinese ash (Fraxinus chinensis) plantation, where they fed on young leaves in large quantities. Ash was planted at this site over 40 years ago as part of a reforestation program, and plantations are invaded by native vegetation. Guans are abundant at this site, and seasonal consumption of ash foliage, a concentrated and abundant food source, may have influenced local population dynamics.

Potential applications of urinary C‐peptide of insulin for comparative energetics research

The study of comparative energetics offers a valuable way to identify broad ecological principles and assess the functional significance of energetic adaptations during the course of evolution. Yet, the quantification of energetic status for nonhuman primates under natural conditions remains one of the most challenging aspects of comparative energetics research. Here, we report on the development of a noninvasive field method for measuring energetic status in great apes, humans, and possibly other nonhuman primates. Specifically, we have explored measurement of a urinary metabolite of insulin (C-peptide) as a physiological marker of energetic condition in chimpanzees and orangutans. We performed three validation studies and successfully measured C-peptide in urine samples from captive chimpanzees, wild chimpanzees, and wild orangutans. Urinary C-peptide measures gave indications of being a reliable signal of energetic status in both species. For chimpanzees and orangutans in the wild, baseline urinary C-peptide levels were higher during periods of fruit abundance than periods of low fruit availability. Urinary C-peptide levels were also higher for well-fed captive chimpanzees compared with wild chimpanzees. Although sample size was small, top-ranking male chimpanzees showed higher C-peptide levels in the wild than low-ranking males only during the period of fruit abundance. These preliminary results indicate that further development of the urinary C-peptide method could expand opportunities to quantify energetic condition for great apes in the wild and generate new data for comparative research. We highlight specific applications for studying great ape reproduction as well as the nutritional ecology of human foragers.

DIET OF THE CAUCA GUAN: EXPLOITATION OF A NOVEL FOOD SOURCE IN TIMES OF SCARCITY

Although exotic species may have a negative impact on native organisms, they can in some cases provide abundant resources. Use of these resources may have important implications for habitat use, movement, and space requirements of native animals, and ultimately for population dynamics. We describe the diet of a population of the narrowly endemic Cauca Guan (Penelope perspicax) in the Colombian Andes. This guan demonstrates plasticity in its eating habits, feeding on an exotic tree species during periods of food scarcity. Based on direct observations and analysis of fecal samples over a one-year cycle, we found that guans fed on 89 species of fruits but also included foliage, flowers, and invertebrates in their diets. Guans fed on fruit species in proportion to their availability but favored some species with high fruit production or prolonged fruiting. Fruit availability, measured both in numbers of species and biomass, varied throughout the year, with a low in September-December. During the period of low fruit availability, guans congregated in large numbers at a Chinese ash (Fraxinus chinensis) plantation, where they fed on young leaves in large quantities. Ash was planted at this site over 40 years ago as part of a reforestation program, and plantations are invaded by native vegetation. Guans are abundant at this site, and seasonal consumption of ash foliage, a concentrated and abundant food source, may have influenced local population dynamics.

Paleoseasonality inferred from equid teeth and intra-tooth isotopic variability

This research presents a study of intra-tooth isotopic variability measured in hypsodont equid teeth as a means of determining paleoseasonality. The purpose of this investigation is to determine whether Sivapithecus, a Miocene hominoid from the Siwaliks of Pakistan, lived in habitats characterized by a seasonal rainfall regime, and if so, what kind of forest is associated with this regime. Forest type, such as evergreen, semi-evergreen, moist deciduous, and dry deciduous, is largely determined by length of the dry period. Reconstruction of the rainfall regime therefore allows inferences of forest type in the fossil record. Seasonal rainfall regimes can be determined from oxygen stable isotopes, for oxygen isotopes track amount of rainfall in tropical regions. Sampling oxygen isotopes along the length of an equid tooth, which takes over a year to develop, therefore provides a record of seasonal isotopic changes in body water, which in turn reflect drinking water and ultimately precipitation. Carbonate oxygen results from Siwalik equid teeth spanning 10.0–6.3 Ma indicate a rainfall regime similar to that experienced by southern China monsoon forests today, with a monsoonal rainy season and a five-to-six month dry season. Furthermore, results suggest a seasonal birthing pattern for Siwalik equids and therefore predictable seasonal regime. These results indicate that Sivapithecus lived under a seasonal regime with dry periods longer than the maximum of 4 months that most great apes experience today. Therefore Sivapithecus may have experienced longer periods of low fruit availability than do modern apes. Either Sivapithecus differed in habitat requirements, or the forest differed in terms of the spatio-temporal variability of fruit compared to modern analogues. Over geologic time, annual rainfall appears to have decreased in the Siwaliks, beginning around the time Sivapithecus became extinct, but annual seasonality of rainfall does not change.

Reproductive Socioecology of Tufted Capuchins (Cebus apella nigritus) in Northeastern Argentina

We describe the reproductive parameters of tufted capuchins (Cebus apella nigritus) in the Iguazu National Park, NE Argentina. We obtained data on six different groups (33 individually recognized adult females) studied for periods of 2–9 years. Estimated birthrate is 0.59 infants per female per year in unprovisioned groups. A group that was provisioned for 6 years during the winter period of low fruit availability (May–August), showed a similar birth rate of 0.61, but a lower infant mortality rate than unprovisioned groups. The birthrate estimated for this population is higher than the one reported for white-faced and wedge-capped capuchins. The mean interbirth interval is 19.35 months, but a female can have infants in successive years, even when her previous infant has survived. The modal age at first delivery is 7 years, which is similar to the one observed in wedge-capped capuchins. When young adult females come into estrous they avoid copulating with the alpha male that sired them, thus providing evidence for a behavioral mechanism of inbreeding avoidance. Births are very seasonal at Iguazu, occurring during the spring and summer months (October–February) when food availability is at its peak. Tufted capuchins at Iguazu are more seasonal breeders than other capuchin populations, probably as a result of their more seasonal environment. The secondary sex ratio does not deviate significantly from 1:1, despite the known ability of capuchins to adjust secondary sex ratio to local conditions.

Dietary Differences Among Sympatric Callitrichinae in Northern Bolivia: Callimico goeldii, Saguinus fuscicollis and S. labiatus

Studies of sympatric species can provide important data to define how dietary and habitat requirements differ among them. I collected dietary data during a first yearlong comparative study of wild groups of Callimico goeldii, Saguinus labiatus and S. fuscicollis. Dietary overlap was highest between Saguinus fuscicollis and Saguinus labiatus throughout the year, and lowest between Saguinus labiatus and Callimico goeldii. All three species had high dietary overlap in February and March when a few abundant fruit species dominated their diets. Although all three species rely heavily on many of the same fruits and arthropods, there are several important distinctions among their diets. Surprisingly, Callimico goeldii consume large quantities of fungus throughout the year: 29% of annual feeding records. Mycophagy is more frequent in the dry season when fruits are scarce. In contrast, Saguinus labiatus rarely eat fungus during the period of fruit scarcity, and instead rely on nectar, a resource never exploited by Callimico goeldii. Saguinus fuscicollis also rely on nectar during periods of low fruit availability and increase their intake of arthropods and exudates. During April, a period of fruit scarcity, exudates comprise >50% of the feeding records of Saguinus fuscicollis. The use of different food resources during fruit scarcity, and differences in the heights at which each species feeds and forages appear to define a distinct ecological niche for each of them and allow them to maintain long-term associations throughout the year. Furthermore, I hypothesize that the limited distribution of Callimico goeldii may result from their restriction to forests that have high disturbance rates, where microhabitats appropriate for fungal growth are abundant, but which also contain abundant fruit and insects.

The Influence of Temporal Changes in Fruit Availability on Diet Composition and Seed Handling in Blue Monkeys (Cercopithecus mitis doggetti)1

ABSTRACTWe investigated the relation between temporally varying resources, diet composition, and seed‐handling behaviors in a group of blue monkeys (Cercopithecus mitis doggetti) in a tropical montane forest of Rwanda. Changes in diet composition were related to concurrent phenological studies of fruit‐producing trees, and density and abundance of tree resources within the monkey's home range. Fruit composed nearly 50 percent of the diet. Over 50 percent of the fruits eaten had juicy fleshy pulp. Observations of seed handling behavior provided insights into the role of these animals as potential seed dispersal agents. The monkeys moved the seeds of 29 species out of parent canopies by defecating seeds intact and by potentially carrying seeds in cheek pouches and dropping them later. Seeds of 18 species were found intact in fecal piles. Our study showed community‐level phenology patterns did not indicate a decrease in fruit availability during the study period, but an analysis of the preferred fruits consumed by the monkeys showed distinct periods of low fruit availability. The study period included two dry seasons; only one of these produced a period of fruit scarcity for the animals. The animals employed different strategies during times of preferred fruit scarcity. They increased consumption of leaves and other fleshy fruits, and diet diversity increased, or became mainly seed predators and diet diversity decreased. The variable responses of these monkeys to changes in food availability highlights their dietary plasticity and imposes significant variations in their role as potential seed dispersers.

Nitrogen and Energy Balance of the Fruit Bat Rousettus aegyptlacus on Natural Fruit Diets

The nitrogen and energy balances of the Egyptian fruit bat, Rousettus aegyptiacus (Pteropodidae), were determined in a series of studies of animals on five single-fruit diets differing in their nutritional content (carob, Ceratonoia siliqua; Persian lilac, Melia azedarach; loquat, Eriobotrya japponica; mulberry, Murus nigra; and sycamore, Ficus sycomorus). It was found that except for Persian lilac, these fruits, which are eaten in nature by the bats, can adequately supply their nitrogen requirements, while Persian lilac and loquat were insufficient for their energy demands. On the basis of average nutrient composition across the tested fruits, the Egyptian fruit bat (mean body mass 144 g) requires a mean intake of 6g dry matter per day for maintaining nitrogen balance, while a mean intake of 11 g dry matter per day is needed in order to fulfill its daily energy requirements. These results suggest that energy, rather than nitrogen, is the limiting nutritional component in the diet of the fruit bat. The maintenance nitrogen requirement determined from the balance studies, 0.247 g N kg-0.75 d⁻¹, is 55% lower than expected from allometric relations. When the lilac diet is excluded, it is even lower: 0.110 g N kg-0.75 d⁻¹ (76% lower than expected). The maintenance nitrogen requirement is also much lower than reported for other species of fruit bats. This may reflect an adaptation to periods of low fruit availability and thus nitrogen shortage within the distribution limits of R. aegyptiacus.

Feeding and Reproduction of Three Didelphid Marsupials in Two Neotropical Forests (French Guiana)

The reproductive patterns of three didelphid marsupial species (Caluromys philander, Didelphis marsupialis and Philander opossum) were studied in secondary and mature forest in French Guiana in relation to food supply and seasonal variation. Both forests exhibited a period of low fruit availability which was longer and more acute in the mature forest. Nevertheless, survival rate of pouch young was higher for C. philander and P. opossum in the mature forest. It was correlated with high nectar availability during the season of fruit scarcity, and with lower population density compared to the secondary forest site. Conversely, D. marsupialis had a more seasonal breeding pattern, with low mortality of pouch young on both sites, and thus appeared less directly dependent on environmental conditions. Annual variations in body weight were compared for the three species on both study areas. Influence of parturition dates, age and body weight of the female upon litter size and pouch young survival is discussed.