Degree Of Frugivory Research Articles

A comparison of inter- and intraspecific variation in seed dispersal in three South American primates

Abstract Primate communities vary in their level of redundancy, or overlap, in seed dispersal function, which could be due to body size, degree of frugivory or intraspecific variation, among other factors. In this study, we quantified redundancy in seed dispersal among three sympatric primate species: Lagothrix lagothricha, Alouatta seniculus and Sapajus apella in gallery forests in Meta, Colombia. We compared the median seed width dispersed and the number and species richness of large (≥5.9 mm wide) and very large (>7.5 mm wide) seeds per faecal sample. The medium-sized, highly folivorous A. seniculus mostly dispersed large seeds, the larger, highly frugivorous L. lagothricha dispersed very large and small seeds, and the smaller, partially frugivorous S. apella dispersed the smallest seeds. However, for L. lagothricha and S. apella, we did not find the expected results that adults disperse larger seeds than juveniles. Across species, there is complementarity in seed dispersal in relation to seed size, with L. lagothricha being unique in its contribution to the dispersal of very large seeds both in terms of quantity and richness.

Factors influencing terrestriality in primates of the Americas and Madagascar.

Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs, and lorises (strepsirrhines), which are mostly arboreal. Numerous ecological drivers and species-specific factors are suggested to set the conditions for an evolutionary shift from arboreality to terrestriality, and current environmental conditions may provide analogous scenarios to those transitional periods. Therefore, we investigated predominantly arboreal, diurnal primate genera from the Americas and Madagascar that lack fully terrestrial taxa, to determine whether ecological drivers (habitat canopy cover, predation risk, maximum temperature, precipitation, primate species richness, human population density, and distance to roads) or species-specific traits (body mass, group size, and degree of frugivory) associate with increased terrestriality. We collated 150,961 observation hours across 2,227 months from 47 species at 20 sites in Madagascar and 48 sites in the Americas. Multiple factors were associated with ground use in these otherwise arboreal species, including increased temperature, a decrease in canopy cover, a dietary shift away from frugivory, and larger group size. These factors mostly explain intraspecific differences in terrestriality. As humanity modifies habitats and causes climate change, our results suggest that species already inhabiting hot, sparsely canopied sites, and exhibiting more generalized diets, are more likely to shift toward greater ground use.

Abundance determines core–periphery roles of birds in a Neotropical seed dispersal network

Frugivorous birds assume different roles in the organization of seed dispersal networks depending on how they interact with plants. Identifying the birds with the most important structural roles can shed light on how seed dispersal systems function. Here, we characterized the seed dispersal network in a megadiverse Neotropical bird community from Brazil and quantitatively scored birds according to their importance in the network. We tested the applicability of the recent core–periphery framework based on stochastic block models and contrasted it with other metrics commonly used in ecological networks to define structurally important species. Then, we also evaluated the main attributes (body mass, degree of frugivory and abundance) associated with the role of frugivorous birds in the network. In the field we recorded 1132 mutualistic interactions between 44 bird species and 41 plant species. We identified the Silver‐beaked Tanager Ramphocelus carbo, Band‐tailed Manakin Pipra fasciicauda and Red‐legged Honeycreeper Cyanerpes cyaneus as the most important seed‐dispersers. Our study highlighted the utility of the core–periphery method in identifying relevant species in the context of networks, which gave slightly different results to other approaches. Specifically, the core–periphery assessment identified more species as relevant, including the large frugivore Bare‐faced Curassow Crax fasciolata. Finally, we discovered that bird abundance was the main predictor of a species' role. We conclude that abundant and generalist frugivorous birds are key components in the maintenance of ecosystem function in the studied ecosystem.

THE DEGREE OF FRUGIVORY OF BIRDS AS ESTIMATED FROM GASTRIC AND FECAL SAMPLES

The degree of frugivory (DF) has long been used to characterize the relative importance of fruits to the diet of a bird and, more recently, as a functional trait related to the role of birds in seed dispersal networks. Although quantitative estimations of DF are desirable, general, categorical classifications or coarse estimations of diet composition based in qualitative information are often used. Data on stomach, fecal and regurgitation contents scattered in the literature or easily obtained in the field could be used to provide a quantitative, potentially more reliable assessment of DF. We compiled such data from the literature and our own fieldwork to obtain 12,576 samples for 985 Neotropical bird species, of which 489 species (49.6%) from 61 families had at least one fruit-containing sample. Gastric (i.e. stomach plus regurgitation) and fecal samples provided similar estimates of DF, despite potential differences in the degree of food digestion. The DF we obtained were higher than those presented in the most frequently used source of quantitative DF estimates in the literature (the Elton Traits database). We further explored with a few study cases the utility of stomach, fecal and regurgitation samples to evaluate intraspecific geographic, sexual, and ontogenetic variations in DF, topics rarely investigated so far. We argued that stomach, fecal and regurgitation sample data abundantly available in the literature or obtained from mist-netted birds may be used to produce quantitative assessments of DF likely more reliable than the estimates used so far and useful for a plethora of ecological studies.

Abundance predominates over niche factors as determinant of the frequency of interactions between frugivorous birds and plants

AbstractNeutral and niche factors influence the structure of frugivory and seed dispersal networks. While the former refers to the abundance of interacting species, niche factors refer to traits that mediate interactions between species (e.g., morphology). The challenge is to unravel in which circumstances one kind of factor predominates over the other, or how much variation is explained by each factor. We investigated the relative contributions of abundance and trait matching (considering fruit's size, pulp mass to seed mass ratio, and lipid content, and bird's degree of frugivory, body mass, and gape width) as drivers of the frequency of interactions between frugivorous birds and fleshy fruits in an area of Cerrado second‐growth vegetation in Brazil. We expected that the abundance of species would be the most important factor due to the predominance of common small‐bodied generalist bird species and small‐seeded fleshy‐fruited plants. Species abundance was indeed an important factor explaining interactions, although in limited fashion. This is because niche factors also helped to explain bird–plant interaction frequencies in the community, particularly the mass ratio of fruits and, to a lesser extent, their lipid content through its interaction with abundance and its negative correlation with mass ratio. In addition to the importance of both bird and plant abundances, these results underscore the role played by plant functional traits in maintaining community function and ecosystem services even in habitats dominated by common generalist birds and small‐seeded plants.Abstract in Portuguese is available with online material.

Digest: New insight into sensory trade-off in phyllostomid bats.

Do the relative size of the olfactory bulb, cochlea, and orbit correlate with diet in phyllostomid bats? Hall et al. (2021) found that the degree of frugivory is positively correlated with the relative size of the olfactory bulb and the orbit. The degree of animalivory is negatively correlated with the relative size of the olfactory bulb and the orbit. Finally, the degree of nectarivory is negatively correlated with the relative size of the cochlea.

Degree of Frugivory Predicts Rates of Food-Related Agonism and Intragroup Proximity in Wild Gray Woolly Monkeys (Lagothrix lagotricha cana).

The main factors influencing feeding competition among members of diurnal primate groups are the distribution, availability, and quality of food resources. Socioecological models predict that temporal availability of preferred resources, such as fruit, can influence intragroup feeding competition, which is expected to affect rates of agonism and intragroup spatial patterns. We evaluated the effects of temporal variation in fruit availability on the degree of frugivory (i.e., the proportion of time spent feeding on fruit in relation to total food consumption) and the effects of fruit availability and degree of frugivory on rates of agonistic interactions, and intragroup proximity in two wild groups of gray woolly monkeys (Lagothrix lagotricha cana) in southwestern Brazilian Amazonia. We recorded 227 agonistic interactions via the all occurrences method and 3549 records of spacing via scan sampling during an 8-mo field study from March to October 2017. We found that fruit availability showed a positive relationship with the woolly monkeys’ degree of frugivory, which in turn showed a positive relationship with the rates of agonism. We also found that degree of frugivory positively affected intragroup proximity in periods of lower fruit availability, and that agonistic interactions and proximity covaried positively. Conversely, as the degree of frugivory increased, monkeys exhibited greater interindividual distances and, consequently, lower rates of agonism, consistent with lower levels of feeding competition in periods of higher fruit availability. Therefore, we suggest that intragroup contest competition for fruits is an important cost of group living even for generalized, opportunistic frugivorous primates, such as woolly monkeys.

Fruit abundance and trait matching determine diet type and body condition across frugivorous bird populations

Research on seed‐dispersal mutualisms has been highly unbalanced towards the plants, largely overlooking the fitness effects of fruit resources on frugivorous animals. Moreover, despite morphological mismatches like gape limitation may reduce the abundance of fruits that are actually accessible to a frugivore species, there is very little evidence on the trait‐matching implications from a frugivore's perspective. Here, we refine recent resource‐provisioning models to comprehensively test the joint effects of fruit abundance and trait matching on diet type and body condition (a surrogate of fitness) across frugivorous bird populations: Sardinian warblers Curruca melanocephala inhabiting ten Mediterranean forests differing in the abundance and composition of fleshy fruits. We hypothesised the abundance of fruit resources to have positive effects on the degree of frugivory and body condition of warblers, and such effects to be more pronounced when accounting for both trait matching (accessible fruits) and resource provisioning (energy in accessible fruits). We found a sharp threshold over which warblers shifted from a diet with very little or even no fruits to a predominantly frugivorous diet with increasing the local abundance of accessible fruits. We also found a strong positive relationship between the abundance of accessible fruits and the body condition of warblers (body mass and residual body mass), an effect that was more pronounced in females than in males. Although diet type and body condition were much better predicted when accounting for trait matching, accounting for resource provisioning did not improve the explanatory power of fruit resources. The fact that we detected strong and sex‐dependent effects of fruit resources on body condition just a few weeks before the breeding season suggests that fruit resources likely affect the timing and success of reproduction, a question that deserves further research. Our findings provide new insight into the fitness consequences of seed‐dispersal mutualisms for frugivorous animals.

Prenatal Androgen Effects as a Proximate Mechanism Underpinning Variation in Social Behavior Among Female Nonhuman Primates

While the role of ecological factors in shaping primate social systems has been a central focus for decades, less attention has been given to phylogenetic relationships and the potential role of underlying proximate mechanisms. This study aimed to investigate the relationship between one such proximate mechanism, prenatal androgen effects (PAEs), and aspects of social behavior in female nonhuman primates using the 2D:4D ratio as a proxy for PAEs and phylogenetically controlled methods. In general, female 2D:4D ratios were highest in monogamous species (low inferred PAEs) and lowest in polygynandrous and polygynous species (high inferred PAEs). 2D:4D ratios also varied with the form of polygyny/polygynandry, potentially with regard to the need for competitive over cooperative behaviors and the intensity of female reproductive competition. Species characterized by female dominance had lower 2D:4D ratios than species characterized by male dominance or codominance. There were no significant relationships between 2D:4D ratio and either degree of frugivory or group size. Relationships between 2D:4D ratios and the directional consistency index and 2D:4D ratios and rates of female–female agonism were also nonsignificant although sample sizes for both of these variables were small. Female social relationships are a manifestation of complex competitive and cooperative behaviors and the results suggest that PAEs may act as a proximate mechanism underlying the expression of certain aspects of behavior in female primates in ways that are adaptive to their social system.

Frugivory Specialization in Birds and Fruit Chemistry Structure Mutualistic Networks across the Neotropics.

AbstractThe interaction between fruit chemistry and the physiological traits of frugivores is expected to shape the structure of mutualistic seed dispersal networks, but it has been understudied compared with the role of morphological trait matching in structuring interaction patterns. For instance, highly frugivorous birds (i.e., birds that have fruits as the main component of their diets), which characteristically have fast gut passage times, are expected to avoid feeding on lipid-rich fruits because of the long gut retention times associated with lipid digestion. Here, we compiled data from 84 studies conducted in the Neotropics that used focal plant methods to record 35,815 feeding visits made by 317 bird species (155 genera in 28 families) to 165 plant species (82 genera in 48 families). We investigated the relationship between the degree of frugivory of birds (i.e., how much of their diet is composed of fruit) at the genus level and their visits to plant genera that vary in fruit lipid content. We used a hierarchical modeling of species communities approach that accounted for the effects of differences in body size, bird and plant phylogeny, and spatial location of study sites. We found that birds with a low degree of frugivory (e.g., predominantly insectivores) tend to have the highest increase in visitation rates as fruits become more lipid rich, while birds that are more frugivorous tend to increase visits at a lower rate or even decrease visitation rates as lipids increase in fruits. This balance between degree of frugivory and visitation rates to lipid-poor and lipid-rich fruits provides a mechanism to explain specialized dispersal systems and the occurrence of certain physiological nutritional filters, ultimately helping us to understand community-wide interaction patterns between birds and plants.

Do primates flexibly use spatio-temporal cues when foraging?

Foraging in seasonal environments can be cognitively demanding. Comparative studies have associated large brain size with a frugivorous diet. We investigated the ability of three semi-free-ranging primate species with different degrees of frugivory (Ntrials: Macaca tonkeana = 419, Macaca fascicularis = 197, Sapajus apella = 346) in developing a mental representation of the spatio-temporal distribution of food using foraging experiments. Forty-two boxes were fixed on trees, and each week ("season"), some of them were filled with fruits which were either highly preferred, or less preferred. Spatial (geometrical panels) and temporal (peel skin of the available fruit) cues were present at each season to indicate where (food location), what (which food) was available, and when. To test the flexible use of the cues in primate foraging behaviour, we first removed the spatial and temporal cues one at a time, and then, we manipulated the "seasonal" order of the available fruit. We compared the foraging performances in the absence and the presence of the cues and during the usual and unusual seasonal order. The average proportion of baited boxes chosen by the subjects in presence of both cues was high (between 73% and 98%) for all species. The primates seemed to remember the spatio-temporal food availability (or used other cues) because no difference was found between trials with or without our spatial and temporal cues. When the usual seasonal pattern was changed, they flexibly adjusted the feeding choice by using the provided temporal cues. We discuss these results also in view of a possible experimental bias.

Spatial cognition in western gorillas (Gorilla gorilla): an analysis of distance, linearity, and speed of travel routes.

Spatial memory allows animals to retain information regarding the location, distribution, and quality of feeding sites to optimize foraging decisions. Western gorillas inhabit a complex environment with spatiotemporal fluctuations of resource availability, prefer fruits when available, and travel long distances to reach them. Here, we examined movement patterns-such as linearity, distance, and speed of traveling-to assess whether gorillas optimize travel when reaching out-of-sight valued resources. Our results show that gorillas travel patterns are affected by the activity they perform next, the type of food they feed on, and their preference level to specific fruits, suggesting they are able to optimize foraging based on spatial knowledge of their resources. Additionally, gorillas left in the direction of the next resource as soon as they started traveling and decelerated before approaching food resources, as evidence that they have a representation of their exact locations. Moreover, home range familiarity did not influence gorillas' movement patterns, as travel linearity in the core and periphery did not differ, suggesting that they may not depend wholly on a network of paths to navigate their habitat. These results show some overlap with chimpanzees' spatial abilities. Differences between the two ape species exist, however, potentially reflecting more their differences in diet (degree of frugivory) rather than their cognitive abilities. Further studies should focus on determining whether gorillas are able to use shortcuts and/or approach the same goal from multiple directions to better identify the spatial abilities used by this species.

Where and what? Frugivory is associated with more efficient foraging in three semi-free ranging primate species.

Foraging in seasonal environments can be cognitively challenging. Comparative studies have associated brain size with a frugivorous diet. We investigated how fruit distribution (where) and preference (what) affect foraging decisions in three semi-free ranging primate species with different degrees of frugivory: Macaca tonkeana (Nindiv = 5; Ntrials = 430), M. fascicularis (Nindiv = 3; Ntrials = 168) and Sapajus apella (Nindiv = 6; Ntrials = 288). We used 36 boxes fixed on trees and filled with highly and less preferred fruits with different (weekly) spatio-temporal distributions. Individuals were tested in two conditions: (1) same fruit provided concurrently in the same quantity but in a scattered and in a clumped distribution, (2) highly preferred fruit was scattered while the less preferred was clumped. Generally, primates preferred feeding first on the boxes of the clumped distribution in both conditions, with the more frugivorous species at a higher degree than the less frugivorous species in condition (1), but not (2). Therefore, what fruit was available changed the foraging decisions of the more frugivorous species who also engaged more in goal-directed travel. When feeding on preferred fruit, primates probably maximized foraging efficiency regardless of their degree of frugivory. Our findings emphasize that the food type and distribution may be a preponderant driver in cognitive evolution.

Abundance and size of birds determine the position of the species in plant-frugivore interaction networks in fragmented forests

The relationships between frugivorous animals and plants are of vital importance particularly in tropical forests. The way species interact and how they are organized within interaction networks could be determined by their ecological and morphological characteristics. This study evaluates the hypothesis that the topological position of species within an interaction network is determined by their degree of frugivory, body size, and abundance. Thus, we constructed the frugivory network between birds and plants in a rainforest fragment in northwestern Colombia. The position of the species within the network was calculated based on three centrality measures (degree, betweenness, and closeness), and its association with relative abundance, degree of frugivory, and body size of each bird species was evaluated by means of a generalized linear model. We found that the species that were most abundant and had the smallest body size had central positions in the interaction network. This pattern is contrary to what has been observed in pristine forests, where species with large body size are more important for network stability. Our results suggest that forest fragmentation modifies the roles of species within the network structure, in part, due to changes in the makeup of the original frugivore community. The information presented may be useful to evaluate the effects of the loss of species as a result of anthropic actions, with the aim of generating ecosystem restoration strategies.

Functional responses of avian frugivores to variation in fruit resources between natural and fragmented forests

Abstract Partner choice in species interaction networks, that is, between frugivorous birds and fruiting plants, is largely determined by matching of functional traits. However, the composition of functional traits in plant communities changes along land‐use gradients. Understanding how flexible consumers react to changes in the trait composition of resources is crucial to project consequences for ecosystem functions, such as seed dispersal. We investigated the ability of birds to consume fruits with different sets of traits in natural and fragmented tropical montane forests across an elevational gradient. We developed a novel, trait‐based approach to quantify the functional shifts of consumers between resources with different functional traits. We expected the degree of functional shifts to be associated with bird traits related to food choice, such as bill width and degree of frugivory, as well as foraging behaviour, such as wing shape and foraging stratum. We sampled the plant–frugivore networks at three elevations and two habitat types (natural and fragmented forest) and measured the functional traits for each plant and bird species. We calculated the trait space of the plant community at each elevation and projected the interacting birds into it. Finally, we calculated the functional shift, which is the trait‐based distance between the preferred fruit resources in the two habitat types for each bird species. We found differences in the functional trait space of the fruiting plant community between natural and fragmented forests across all elevations. Birds' observed functional shifts between habitat types at each elevation were generally larger than the shifts expected by null models. Wing shape was the most important trait related to the functional shifts across the elevational gradient, whereas bill width, degree of frugivory, foraging stratum and phylogeny were not important. We conclude that birds with pointed wings respond flexibly to changes in the trait composition of fruit resources, probably due to the high mobility of these species. Our results emphasize that linking species interaction networks and functional trait analyses yield new insights into how consumer species respond to changes in biotic factors and can improve projections of how human impacts modify trophic interactions and associated ecosystem functions. A plain language summary is available for this article.

Seed‐dispersal networks are more specialized in the Neotropics than in the Afrotropics

AbstractAimBiogeographical comparisons of interaction networks help to elucidate differences in ecological communities and ecosystem functioning at large scales. Neotropical ecosystems have higher diversity and a different composition of frugivores and fleshy‐fruited plants compared with Afrotropical systems, but a lack of intercontinental comparisons limits understanding of (a) whether plant–frugivore networks are structured in a similar manner, and (b) whether the same species traits define the roles of animals across continents.LocationAfrotropics and Neotropics.Time period1977–2015.TaxaFleshy‐fruited plants and frugivorous vertebrates.MethodsWe compiled a dataset comprising 17 Afrotropical and 48 Neotropical weighted seed‐dispersal networks quantifying frugivory interactions between 1,091 fleshy‐fruited plant and 665 animal species, comprising in total 8,251 interaction links between plants and animals. In addition, we compiled information on the body mass of animals and their degree of frugivory. We compared four standard network‐level metrics related to interaction diversity and specialization, accounting for differences related to sampling effort and network location. Furthermore, we tested whether animal traits (body mass, degree of frugivory) differed between continents, whether these traits were related to the network roles of species and whether these relationships varied between continents.ResultsWe found significant structural differences in networks between continents. Overall, Neotropical networks were less nested and more specialized than Afrotropical networks. At the species level, a higher body mass and degree of frugivory were associated with an increasing diversity of plant partners. Specialization of frugivores increased with the degree of frugivory, but only in the Neotropics.Main conclusionsOur findings show that Afrotropical networks have a greater overlap in plant partners among vertebrate frugivores than the more diverse networks in the Neotropics that are characterized by a greater niche partitioning. Hence, the loss of frugivore species could have stronger impacts on ecosystem functioning in the more specialized Neotropical communities compared with the more generalized Afrotropical communities.

Macaques as Seed Dispersal Agents in Asian Forests: A Review

The role of primates in seed dispersal is well recognized. Macaques (Macaca spp.) are major primate seed dispersers in Asia, and recent studies have revealed their role as seed dispersal agents in this region. Here, we review present knowledge of the traits that define the role of macaques as seed dispersers. The size of seeds in fruit influences whether macaques swallow (0.5–17.1 mm; median: 3.0), spit (1–37 mm; median: 7.6), or drop (8.2–57.7 mm; median: 20.5) them. Dispersal distances via defecation are several hundreds of meters (median: 259 m, range: 0–1300 m), shorter than those achieved by some mammals and birds in tropical and temperate regions. However, macaques disperse seeds by defecation at comparable distances to omnivorous carnivores, and further than passerines. Seed dispersal distance by spitting is much shorter (median: 20 m, range: 0–405 m) than by defecation. Among Asian primates, seed dispersal distances resulting from macaque defecation are shorter than those for gibbons and longer than those for langurs. The effects of seed ingestion on the percentage and speed of germination vary among both plant and macaque species. The degree of frugivory, fruit/seed handling methods, seed dispersal distance, microhabitats of dispersed seeds, and effects of dispersal on seed germination vary seasonally and interannually, and long-term studies of the ecological role of macaques are needed. Researchers have begun to assess the effectiveness of seed dispersal by macaques, secondary dispersal of seeds originally dispersed by macaques, and the effects of provisioning on seed dispersal. Future studies should also test the effects of social factors (such as age and rank), which have received little attention in studies of seed dispersal.

Low Levels of Fruit Nitrogen as Drivers for the Evolution of Madagascar\u2019s Primate Communities

The uneven representation of frugivorous mammals and birds across tropical regions – high in the New World, low in Madagascar and intermediate in Africa and Asia – represents a long-standing enigma in ecology. Several hypotheses have been proposed to explain these differences but the ultimate drivers remain unclear. Here, we tested the hypothesis that fruits in Madagascar contain insufficient nitrogen to meet primate metabolic requirements, thus constraining the evolution of frugivory. We performed a global analysis of nitrogen in fruits consumed by primates, as collated from 79 studies. Our results showed that average frugivory among lemur communities was lower compared to New World and Asian-African primate communities. Fruits in Madagascar contain lower average nitrogen than those in the New World and Old World. Nitrogen content in the overall diets of primate species did not differ significantly between major taxonomic radiations. There is no relationship between fruit protein and the degree of frugivory among primates either globally or within regions, with the exception of Madagascar. This suggests that low protein availability in fruits influences current lemur communities to select for protein from other sources, whereas in the New World and Old World other factors are more significant in shaping primate communities.

Nutritional correlates of the “lean season”: Effects of seasonality and frugivory on the nutritional ecology of diademed sifakas

Primate field studies often identify "lean seasons," when preferred foods are scarce, and lower-quality, abundant foods (fallback foods) are consumed. Here, we quantify the nutritional implications of these terms for two diademed sifaka groups (Propithecus diadema) in Madagascar, using detailed feeding observations and chemical analyses of foods. In particular, we sought to understand 1) how macronutrient and energy intakes vary seasonally, including whether these intakes respond in similar or divergent ways; 2) how the amount of food ingested varies seasonally (including whether changes in amount eaten may compensate for altered food quality); and 3) correlations between these variables and the degree of frugivory. In the lean season, sifakas shifted to non-fruit foods (leaves and flowers), which tended to be high in protein while low in other macronutrients and energy, but the average composition of the most used foods in each season was similar. They also showed dramatic decreases in feeding time, food ingested, and consequently, daily intake of macronutrients and energy. The degree of frugivory in the daily diet was a strong positive predictor of feeding time, amount ingested and all macronutrient and energy intakes, though season had an independent effect. These results suggest that factors restricting how much food can be eaten (e.g., handling time, availability, or intrinsic characteristics like fiber and plant secondary metabolites) can be more important than the nutritional composition of foods themselves in determining nutritional outcomes-a finding with relevance for understanding seasonal changes in behavior, life history strategies, competitive regimes, and conservation planning.

Seasonal effects on great ape health: a case study of wild chimpanzees and Western gorillas.

Among factors affecting animal health, environmental influences may directly or indirectly impact host nutritional condition, fecundity, and their degree of parasitism. Our closest relatives, the great apes, are all endangered and particularly sensitive to infectious diseases. Both chimpanzees and western gorillas experience large seasonal variations in fruit availability but only western gorillas accordingly show large changes in their degree of frugivory. The aim of this study is to investigate and compare factors affecting health (through records of clinical signs, urine, and faecal samples) of habituated wild ape populations: a community (N = 46 individuals) of chimpanzees (Pan troglodytes) in Kanyawara, Kibale National Park (Uganda), and a western gorilla (G. gorilla) group (N = 13) in Bai Hokou in the Dzanga-Ndoki National Park (Central African Republic). Ape health monitoring was carried out in the wet and dry seasons (chimpanzees: July–December 2006; gorillas: April–July 2008 and December 2008–February 2009). Compared to chimpanzees, western gorillas were shown to have marginally greater parasite diversity, higher prevalence and intensity of both parasite and urine infections, and lower occurrence of diarrhea and wounds. Parasite infections (prevalence and load), but not abnormal urine parameters, were significantly higher during the dry season of the study period for western gorillas, who thus appeared more affected by the large temporal changes in the environment in comparison to chimpanzees. Infant gorillas were the most susceptible among all the age/sex classes (of both apes) having much more intense infections and urine blood concentrations, again during the dry season. Long term studies are needed to confirm the influence of seasonal factors on health and parasitism of these great apes. However, this study suggest climate change and forest fragmentation leading to potentially larger seasonal fluctuations of the environment may affect patterns of ape parasitism and further exacerbate health impacts on great ape populations that live in highly seasonal habitats.