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For energetically limited organisms, life‐history theory predicts trade‐offs between reproductive effort and somatic maintenance. This is especially true of female mammals, for whom reproduction presents multifarious energetic and physiological demands.Here, we examine longitudinal changes in the gut virome (viral community) with respect to reproductive status in wild mature female chimpanzees Pan troglodytes schweinfurthii from two communities, Kanyawara and Ngogo, in Kibale National Park, Uganda.We used metagenomic methods to characterize viromes of individual chimpanzees while they were cycling, pregnant and lactating.Females from Kanyawara, whose territory abuts the park's boundary, had higher viral richness and loads (relative quantity of viral sequences) than females from Ngogo, whose territory is more energetically rich and located farther from large human settlements. Viral richness (total number of distinct viruses per sample) was higher when females were lactating than when cycling or pregnant. In pregnant females, viral richness increased with estimated day of gestation. Richness did not vary with age, in contrast to prior research showing increased viral abundance in older males from these same communities.Our results provide evidence of short‐term physiological trade‐offs between reproduction and infection, which are often hypothesized to constrain health in long‐lived species. [ABSTRACT FROM AUTHOR]

Objectives: This study examines the sensitivity of the development of the dorsal metacarpal ridge (DMR) to the frequency of knuckle‐walking during ontogeny in chimpanzees, and compares the prevalence and prominence of the DMR in hominoids and baboons. Materials and Methods: We characterized the type and frequency of quadrupedalism of wild chimpanzees of different ages from the Ngogo community, Uganda. Using museum specimens, we quantified third metacarpal DMR angle and height in Pan individuals of different developmental stages, and in adult Gorilla, Pongo, Hylobates, and Papio. Results: When terrestrial, all quadrupedalism consisted of knuckle‐walking, although older individuals knuckle‐walked more than younger. The total amount of quadrupedalism engaged in by different age groups while arboreal was consistent; however, knuckle usage while arboreally quadrupedal increased with age. The DMR ridge did not emerge in Pan until older infancy, after the onset of knuckle‐walking, and reached prominence by the juvenile stage. The DMR angle increased significantly after juvenility but relative height did not. Adult Pan and Gorilla have more prevalent and prominent DMRs than Papio; the DMR was rare in Pongo and absent in Hylobates. Discussion: The timing of development of the DMR in chimpanzees supports it as a knuckle walking character, as does its occurrence in gorillas, and virtual absence in suspensory orangutans and gibbons. The DMR in baboons differs in appearance and frequency from DMRs in African apes, and so differentiates knuckle‐walking from digitigrady in catarrhines. The relationship between the DMR and loading of a vertical hand while terrestrial deserves further study. [ABSTRACT FROM AUTHOR]

Viral infection is a major cause of ill health in wild chimpanzees (Pan troglodytes), but most evidence to date has come from conspicuous disease outbreaks with high morbidity and mortality. To examine the relationship between viral infection and ill health during periods not associated with disease outbreaks, we conducted a longitudinal study of wild eastern chimpanzees (P. t. schweinfurthii) in the Kanyawara and Ngogo communities of Kibale National Park, Uganda. We collected standardized, observational health data for 4 years and then used metagenomics to characterize gastrointestinal viromes (i.e., all viruses recovered from fecal samples) in individual chimpanzees before and during episodes of clinical disease. We restricted our analyses to viruses thought to infect mammals or primarily associated with mammals, discarding viruses associated with nonmammalian hosts. We found 18 viruses (nine of which were previously identified in this population) from at least five viral families. Viral richness (number of viruses per sample) did not vary by health status. By contrast, total viral load (normalized proportion of sequences mapping to viruses) was significantly higher in ill individuals compared with healthy individuals. Furthermore, when ill, Kanyawara chimpanzees exhibited higher viral loads than Ngogo chimpanzees, and males, but not females, exhibited higher infection rates with certain viruses and higher total viral loads as they aged. Post‐hoc analyses, including the use of a machine‐learning classification method, indicated that one virus, salivirus (Picornaviridae), was the main contributor to health‐related and community‐level variation in viral loads. Another virus, chimpanzee stool‐associated virus (chisavirus; unclassified Picornavirales), was associated with ill health at Ngogo but not at Kanyawara. Chisavirus, chimpanzee adenovirus (Adenoviridae), and bufavirus (Parvoviridae) were also associated with increased age in males. Associations with sex and age are consistent with the hypothesis that nonlethal viral infections cumulatively reflect or contribute to senescence in long‐lived species such as chimpanzees. Research Highlights: Some viruses of wild primates are relatively benign but may be useful as biomarkers of physiology and health.We used metagenomic methods to characterize viral communities in feces of wild chimpanzees in two long‐term study communities (Kanyawara and Ngogo) in Kibale National Park, Uganda.Chimpanzees exhibited higher viral loads (normalized abundances of viral genetic sequences) when they were ill than when those same individuals were previously healthy.When ill, Kanyawara chimpanzees exhibited higher viral loads than Ngogo chimpanzees, and males, but not females, exhibited higher viral loads as they aged. [ABSTRACT FROM AUTHOR]

I have spent over 40 years studying the behavior of our closest living relatives, the apes. In this paper, I review my research on the spacing, mating, and vocal behavior of gibbons and orangutans (Pongo pygmaeus) and the vocal and social behavior of chimpanzees (Pan troglodytes). I devote special attention to results derived from a 25‐year‐long study of a remarkable and extraordinarily large group of chimpanzees that has recently fissioned at Ngogo in Kibale National Park, Uganda. I conclude with some advice for the next generation of field primatologists. Research Highlights: I review the results of my field research on gibbons, orangutans, and chimpanzees.My findings provide insights into the spacing, mating, and vocal behavior of gibbons and orangutans and the vocal and social behavior of chimpanzees. [ABSTRACT FROM AUTHOR]

Fruit production in tropical forests varies considerably in space and time, with important implications for frugivorous consumers. Characterizing temporal variation in forest productivity is thus critical for understanding adaptations of tropical forest frugivores, yet long‐term phenology data from the tropics, in particular from African forests, are still scarce. Similarly, as the abiotic factors driving phenology in the tropics are predicted to change with a warming climate, studies documenting the relationship between climatic variables and fruit production are increasingly important. Here, we present data from 19 years of monitoring the phenology of 20 tree species at Ngogo in Kibale National Park, Uganda. Our aims were to characterize short‐ and long‐term trends in productivity and to understand the abiotic factors driving temporal variability in fruit production. Short‐term (month‐to‐month) variability in fruiting was relatively low at Ngogo, and overall fruit production increased significantly through the first half of the study. Among the abiotic variables, we expected to influence phenology patterns (including rainfall, solar irradiance, and average temperature), only average temperature was a significant predictor of monthly fruit production. We discuss these findings as they relate to the resource base of the frugivorous vertebrate community inhabiting Ngogo. [ABSTRACT FROM AUTHOR]

ABSTRACT Objectives Recent studies indicate that the locomotor behavior of wild chimpanzees changes during development. Before transitioning to quadrupedal knuckle-walking in adulthood, young chimpanzees engage in a significant amount of upper limb loading suspensory behavior. We investigated whether these dramatic changes in locomotion influence the strength and shape of chimpanzee long bones. Materials and Methods We examined changes in chimpanzee arboreal locomotion over the course of development using behavioral data collected on wild chimpanzees. We measured the midshaft geometric properties of femora and humeri of wild-caught individuals housed in museum collections using micro computed tomographic scans. Results Chimpanzees spent less time moving arboreally as they aged. Femoral/humeral strength ratios also increased with age, as predicted by the changing loading environment during development. Additional analyses revealed that femoral shape, but not humeral shape, varied across chimpanzee age classes. Adult femora were more elliptical compared with those of infants. This change in adult femora is consistent with the observation that adult chimpanzees spend most of their time moving terrestrially and consequently experience a less variable loading environment than do infants. Discussion Taken together, these findings contribute to our understanding of how ontogenetic changes in function affect form. As similar changes may have characterized the behavioral and skeletal ontogeny of extinct hominoids including hominins, these findings furnish a potential means to make inferences about the behavior of fossil taxa based on the structural properties of their bones. Am J Phys Anthropol 160:16-29, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Primate feeding behavior varies over long (e.g., weekly, seasonally, yearly) and short (e.g., hourly) scales of time due to changes in resource availability and the nutritional composition of foods. While the factors that affect long-term changes in feeding behavior have received considerable attention, few data exist regarding what drives variability in feeding behavior over the course of a single day. To address this problem, we investigated diurnal variation in chimpanzee feeding on the leaves of two species of saplings, Pterygota mildbraedii and Celtis africana, at Ngogo, Kibale National Park, Uganda. Specifically, we related short-term changes in chimpanzee feeding behavior on these leaves to diurnal variation in their nutritional composition. Results showed that chimpanzees fed on the leaves of both saplings more in the evening than they did in the morning. The nutritional quality of leaves also improved over the course of the day. Concentrations of cellulose and lignin were lower and total nonstructural carbohydrates (including sugars and starch) were higher in the evening for P. mildbraedii, and sugars were higher in the evening for C. africana. These data suggest that chimpanzees consume these resources when their quality is highest, and consequently, may track the nutrient composition of their foods over very short periods that span only a few hours. In the future, foods collected for analyses must control for time of sampling to ensure biologically meaningful assays of nutrient composition. Am. J. Primatol. 75:342-349, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Highly frugivorous primates like chimpanzees ( Pan trogolodytes) must contend with temporal variation in food abundance and quality by tracking fruit crops and relying more on alternative foods, some of them fallbacks, when fruit is scarce. We used behavioral data from 122 months between 1995 and 2009 plus 12 years of phenology records to investigate temporal dietary variation and use of fallback foods by chimpanzees at Ngogo, Kibale National Park, Uganda. Fruit, including figs, comprised most of the diet. Fruit and fig availability varied seasonally, but the exact timing of fruit production and the amount of fruit produced varied extensively from year to year, both overall and within and among species. Feeding time devoted to all major fruit and fig species was positively associated with availability, reinforcing the argument that chimpanzees are ripe fruit specialists. Feeding time devoted to figs-particularly Ficus mucuso (the top food)-varied inversely with the abundance of nonfig fruits and with foraging effort devoted to such fruit. However, figs contributed much of the diet for most of the year and are best seen as staples available most of the time and eaten in proportion to availability. Leaves also contributed much of the diet and served as fallbacks when nonfig fruits were scarce. In contrast to the nearby Kanywara study site in Kibale, pith and stems contributed little of the diet and were not fallbacks. Fruit seasons (periods of at least 2 months when nonfig fruits account for at least 40% of feeding time; Gilby & Wrangham., Behavioral Ecology and Sociobiology 61:1771-1779, 2007) were more common at Ngogo than Kanyawara, consistent with an earlier report that fruit availability varies less at Ngogo [Chapman et al., African Journal of Ecology 35:287-302, 1997]. F. mucuso is absent at Kanyawara; its high density at Ngogo, combined with lower variation in fruit availability, probably helps to explain why chimpanzee population density is much higher at Ngogo. [ABSTRACT FROM AUTHOR]

Chimpanzees ( Pan troglodytes) are ecologically flexible omnivores with broad diets comprising many plant and animal foods, although they mostly eat fruit (including figs). Like other ecologically flexible nonhuman primates (e.g., baboons, Papio spp.) with broad diets, their diets vary across habitats. Much data on diets come from short studies that may not capture the range of variation, however, and data are scant on variation within habitats and populations. We present data on diet composition and diversity for chimpanzees at Ngogo, in Kibale National Park, Uganda, collected over a 15-year period, with a focus on the plant components of the diet. We compare Ngogo data to those on chimpanzees at the nearby Kibale site of Kanyawara, on other chimpanzee populations, and on some other frugivorous-omnivorous primates. Results support the argument that chimpanzees are ripe fruit specialists: Ngogo chimpanzees ate a broad, mostly fruit-based diet, feeding time devoted to fruit varied positively with fruit availability, and diet diversity varied inversely with fruit availability. Comparison of Ngogo and Kanyawara shows much similarity, but also pronounced within-population dietary variation. Chimpanzees fed much more on leaves, and much less on pith and stems, at Ngogo. Figs accounted for somewhat less feeding time at Ngogo, but those of Ficus mucuso were quantitatively the most important food. This species is essentially absent at Kanayawara; its abundance and high productivity at Ngogo, along with much higher abundance of several other important food species, help explain why chimpanzee community size and population density are over three times higher at Ngogo. High inter-annual variation at Ngogo highlights the value of long-term data for documenting the extent of ecological variation among chimpanzee populations and understanding how such variation might affect population biology and social dynamics. Am. J. Primatol. 73:1-16, 2011. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Chimpanzees (Pan troglodytes) have hostile intergroup relations throughout most or all of their geographic range. Hostilities include aggressive encounters between members of neighboring communities during foraging and during patrols in which members of one community search for neighbors near territory boundaries. Attacks on neighbors involve coalitions of adult males, and are sometimes fatal. Targets include members of all age/sex classes, but the risk of lethal intergroup coalitionary aggression is highest for adult males and infants, and lowest for sexually swollen females. The best-supported adaptive explanation for such behavior is that fission-fusion sociality allows opportunities for low-cost attacks that, when successful, enhance the food supply for members of the attackers' community, improve survivorship, and increase female fertility. We add to the database on intergroup coalitionary aggression in chimpanzees by describing three fatal attacks on adult males, plus a fourth attack on an adult male and an attack on a juvenile that were almost certainly fatal. Observers saw four of these attacks and inferred the fifth from forensic and behavioral evidence. The attackers were males in two habituated, unprovisioned communities (Ngogo and Kanyawara) in Kibale National Park, Uganda. We also summarize data on other intercommunity attacks at Ngogo. Our observations are consistent with the “imbalance of power” hypothesis [Manson & Wrangham, Current Anthropology 32:369–390, 1991] and support the argument that lethal coalitionary intergroup aggression by male chimpanzees is part of an evolved behavioral strategy. Am. J. Primatol. 68:161-180, 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Demography provides critical data to increase our understanding of the evolution, ecology, and conservation of primate populations. The chimpanzees of the Mahale Mountains National Park, Tanzania, have been studied for more than 34 yr on the basis of individual identification and standardized attendance records. From this long-term study, we derived the following demographic data: The major cause of death was disease (48%), followed by senescence (24%) and within-species aggression (16%). Fifty percent of Mahale chimpanzees died before weaning. The median ages of female life history variables were: first maximal swelling, 10.0 yr (n=5); emigration, 11.0 yr (n=11); and first birth, 13.1 yr (n=5). The median period of adolescent infertility was 2.8 yr (n=4) when calculated from the age at immigration to that at first birth. Female fecundity was highest between 20 and 35 yr of age, with an annual birth rate of 0.2. Twenty-six females that were observed from a young age (10–13 yr) to death at various ages (15–40 yr) gave birth to an average of 3.9 and weaned an average of 1.4 offspring. Twenty-five females that were observed from middle age (18–33 yr) to death in older age (31–48) gave birth to an average of 2.7 and weaned an average of 2.0 offspring. The post-reproductive lifespan for female chimpanzees was defined as the number of years that passed from the year when the last offspring was born to the year when the female died, minus 5. Twenty-five percent of old females had a post-reproductive lifespan. The interbirth interval after the birth of a son (&xmacr; = 72 mo) tended to be longer than that after the birth of a daughter (&xmacr; = 66 mo). The extent of female transfer, which is a rule in chimpanzees, is influenced by the size and composition of the unit group and size of the overall local community. Am. J. Primatol. 59:99–121, 2003. © 2003 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated the demographic effects on the hunting behavior of a community of wild chimpanzees at Ngogo in the Kibale National Park, Uganda. Methods; Results; Discussion and comparisons with other studies.

Primate social groups frequently contain multiple males. Male group size has been hypothesized to result from male mating competition, but the selective factors responsible for the evolution of multimale groups are unclear. Short breeding seasons create situations that are not conducive for single males to monopolize mating access to females, and may therefore favor the formation of large male groups. Alternately, since the costs of mate defense increase with the spatial clumping of females, female group size may be a primary determinant of the number of males in a primate group. We used comparative methods designed to control for the potentially confounding effects of hidden third variables associated with phylogeny to test the breeding season and female group size hypotheses for the evolution of multimale groups. Our results revealed no association between breeding season duration and the number of males in groups. In contrast, we provide support for the female group size hypothesis by demonstrating a strong pattern of correlated evolution between female and male group size. [ABSTRACT FROM AUTHOR]

Chimpanzees emit a loud, species-typical long distance call known as the pant hoot. Geographic variation between the pant hoots of chimpanzees living in two neighboring populations, the Mahale Mountains and Gombe Stream National Parks, Tanzania, was examined. Analysis of six acoustic features revealed subtle differences in the way chimpanzees from the two populations called. Individuals from the Mahale study site uttered one section of their pant hoots at a faster rate and with shorter elements than animals from Gombe Stream. In addition, individuals at Mahale delivered broader-band, higher pitched "climax" elements than males from Gombe. While genetic factors, anatomical differences, variations in the use of calls at the two sites, and changes in calling over time may account for the variability between populations, we suggest the additional possibility that differences in pant hooting may be due to learning. [ABSTRACT FROM AUTHOR]

Acoustic analyses and field playback experiments were conducted to investigate interspecific song differences and discrimination in male gibbons. Songs were recorded and analyzed from males of three populations: agile gibbons (Hylobates agilis) in West Kalimantan and South Sumatra and Müller's gibbons (Hylobates muelleri) in East Kalimantan. Male songs from each of the three populations were played back to West Kalimantan agile gibbons. Acoustic analyses indicated that the songs of the two Species differed in spectral features and in the temporal patterning of syllables. Agile gibbon songs from the West Kalimantan and South Sumatran populations varied in song durations and in the maximum frequencies of one song element. Field playbacks showed that West Katimantan agile gibbons respond in a similar manner to local songs and to conspecific songs from South Sumatra. In contrast, the animals responded differentially to conspecific and heterospecific Müller's gibbon songs. These results indicate that gibbons discriminate specific differences in songs, and support the division of agile and Müller's gibbons into distinct species. [ABSTRACT FROM AUTHOR]

Social relationships play an important role in animal behavior. Bonds with kin provide indirect fitness benefits, and those with nonkin may furnish direct benefits. Adult male chimpanzees (Pan troglodytes) exhibit social bonds with maternal brothers as well as unrelated adult males, facilitating cooperative behavior, but it is unclear when these bonds develop. Prior studies suggest that social bonds emerge during adolescence. Alternatively, bonds may develop during adulthood when male chimpanzees can gain fitness benefits through alliances used to compete for dominance status. To investigate these possibilities and to determine who formed bonds, we studied the social relationships of adolescent and young adult male chimpanzees (N = 18) at Ngogo in Kibale National Park, Uganda. Adolescent male chimpanzees displayed social bonds with other males, and they did so as often as did young adult males. Adolescent and young adult males frequently joined subgroups with old males. They spent time in proximity to and grooming with old males, although they also did so with their age peers. Controlling for age and age difference, males formed strong association and proximity relationships with their maternal brothers and grooming relationships with their fathers. Grooming bonds between chimpanzee fathers and their adolescent and young adult sons have not been documented before and are unexpected because female chimpanzees mate with multiple males. How fathers recognize their sons and vice versa remains unclear but may be due to familiarity created by relationships earlier in development. Research Highlights: Adolescent male chimpanzees form social bonds with other males.Bonds were common between unrelated males, but frequent with maternal brothers, peers, old males, and fathers.Fathers may be important for male chimpanzees transitioning to adulthood. [ABSTRACT FROM AUTHOR]

The activity budgets of individual orangutans were investigated at the Kutai Reserve, Indonesia. Activity profiles within and between individuals were compared to examine monthly variations in feeding patterns, potential energetic constraints imposed by large body size and parturition, and the costs of sociality. Animals showed monthly changes in travelling, feeding, and resting patterns. Monthly increases in travelling and feeding were associated with marked reductions in the time spent resting. Inter-individual variations in activity budgets did not exist among animals of the same age-sex class. Activity patterns differed, however, as a function of age and sex. Adult females and subadult males travelled and fed significantly longer than an adult male. Parturition had predictable effects on activity; one female reduced her feeding and travelling immediately following parturition. Adult male orangutan sociality appears to be limited by travel costs. Associations with females forced a male orangutan to travel significantly more compared with periods in which he was solitary. The male did not lose an appreciable amount of time feeding when accompanying a female., (Copyright © 1989 Wiley‐Liss, Inc., A Wiley Company.)