Publications

the significance of fibrous foods for kibale forest chimpanzees.	four categories of plant food dominated the diet of chimpanzees in kibale forest, uganda: non-fig tree fruits, fig tree fruits, herbaceous piths and terrestrial leaves. fruit abundance varied unpredictably, more among non-figs than figs. pith intake was correlated negatively with fruit abundance and positively with rainfall, whereas leaf intake was not influenced by fruit abundance. piths typically have low sugar and protein levels. compared with fruits and leaves they are consistently high in h ...	1991	1685575
contrasting chimpanzees and bonobos: nearest neighbor distances and choices.	in an effort to understand factors underlying differences in the social organization of pan troglodytes and p. paniscus, we measured the nearest neighbor distances and choices for chimpanzees in kibale national park, uganda, and for bonobos in lomako forest, zaire. we assume that the spatial organization of a set of individuals should reflect the underlying relationships between them. bonobos were found to have smaller nearest neighbor distances than chimpanzees. the distribution and variability ...	1994	7797164
seed handling in chimpanzees (pan troglodytes) and redtail monkeys (cercopithecus ascanius): implications for understanding hominoid and cercopithecine fruit-processing strategies and seed dispersal.	primates are confronted with an array of constraints in feeding on fruit, including the removal of adhesive, energy-rich pulp from seeds. in this paper, i discuss how primates meet this challenge and present data on the fruit-processing and seed-handling behavior of chimpanzees and redtail monkeys in kibale national park, uganda. these data are then related to these species' services as seed dispersers. particular attention was paid to the methods by which primates removed pulp from seeds, the d ...	1999	10407465
demographic influences on the hunting behavior of chimpanzees.	we investigated hunting in an unusually large community of wild chimpanzees at ngogo in the kibale national park, uganda. aspects of predation were recorded with respect to the prey, the predators, and hunting episodes. during 23 months of observation, the ngogo chimpanzees caught 128 prey items from four primate and three ungulate species. chimpanzees preyed selectively on immature red colobus primarily during group hunts, with adult males making the majority of kills. party size and compositio ...	1999	10423261
intestinal parasites of the chimpanzee pan troglodytes in kibale forest, uganda.	one-hundred-and-twenty-three stool samples were examined from 45 chimpanzees in a natural population in western uganda. comparison with previous studies is complicated by the diversity of techniques used and interpretations. the ugandan population had relatively many intestinal protozoa, including the probably beneficial entodiniomorph ciliates. strongyloid nematodes are universal among chimpanzees, but were surprisingly absent from those on mount assirik in senegal. railletina tapeworms are spo ...	2000	10827872
recognizing hominoid-modified bones: the taphonomy of colobus bones partially digested by free-ranging chimpanzees in the kibale forest, uganda.	we present a taphonomic study of bones that have passed though the digestive tracts of free-ranging chimpanzees from the kibale forest in uganda. the bone assemblage can be characterized as having a very low species diversity; low number of identifiable specimens (nisp) per scat; bones extremely broken up (very small size range); skeletal part frequencies similar in some ways to those resulting from carnivore partial digestion; and sometimes articulated specimens. modifications to the bones incl ...	2000	11002206
ecological importance of trichromatic vision to primates.	trichromatic colour vision, characterized by three retinal photopigments tuned to peak wavelengths of approximately 430 nm, approximately 535 nm and approximately 562 nm (refs 1, 2), has evolved convergently in catarrhine primates and one genus of new world monkey, the howlers (genus alouatta). this uniform capacity to discriminate red-green colours, which is not found in other mammals, has been proposed as advantageous for the long-range detection of either ripe fruits or young leaves (which fr ...	2001	11268211
new cases of inter-community infanticide by male chimpanzees at ngogo, kibale national park, uganda.	infanticide by males has been recorded in four chimpanzee populations, including that in kibale national park, uganda. some infanticidal attacks occur during inter-community aggression. the sexual selection hypothesis does not easily explain these attacks because they may not directly increase male mating opportunities. however, females in the attackers' community may benefit by expanding their foraging ranges and thereby improving their reproductive success; thus infanticide may increase male r ...	2002	12426461
association between galago thomasi and pan troglodytes schweinfurthii in the kibale national park, uganda.		2003	12778909
foci of endemic simian immunodeficiency virus infection in wild-living eastern chimpanzees (pan troglodytes schweinfurthii).	simian immunodeficiency virus of chimpanzees (sivcpz) is the immediate precursor to human immunodeficiency virus type 1 (hiv-1), yet remarkably, the distribution and prevalence of sivcpz in wild ape populations are unknown. studies of sivcpz infection rates in wild chimpanzees are complicated by the species' endangered status and by its geographic location in remote areas of sub-saharan africa. we have developed sensitive and specific urine and fecal tests for sivcpz antibody and virion rna (vrn ...	2003	12805455
a comparison of buttress drumming by male chimpanzees from two populations.	wild chimpanzees ( pan troglodytes) produce low-frequency sounds by hitting the buttresses and/or trunks of trees. this "buttress drumming" occurs in discrete bouts that may be integrated into the phrase sequence of the chimpanzee's long-distance vocalization, the "pant hoot." the aim of this study was to investigate whether regional variation exists in the drumming behavior of male chimpanzees from kibale national park (kanyawara community), uganda, and taï national park, ivory coast. recording ...	2004	14735390
dominance rank and fecal testosterone levels in adult male chimpanzees (pan troglodytes schweinfurthii) at ngogo, kibale national park, uganda.	in an attempt to describe hormone-behavior interactions in a sample of wild male chimpanzees, we quantified testosterone in 67 fecal samples obtained from 22 adult male chimpanzees at ngogo, kibale national park, uganda. a mixed-model methodology that controlled for age-class identified a significant positive association between testosterone levels and dominance rank. the results are consistent with those reported from a separate, smaller chimpanzee community in the same population in a study th ...	2004	15356859
parasitological analyses of the male chimpanzees (pan troglodytes schweinfurthii) at ngogo, kibale national park, uganda.	numerous intestinal parasites identified in populations of wild nonhuman primates can be pathogenic to humans. furthermore, nonhuman primates are susceptible to a variety of human pathogens. because of increasing human encroachment into previously nonimpacted forests, and the potential for disease transmission between human and nonhuman primate populations, further detailed investigations of primate ecological parasitology are warranted. for meaningful comparisons to be made, it is important for ...	2005	15706587
tool use in insect foraging by the chimpanzees of ngogo, kibale national park, uganda.	chimpanzee tool use for resource acquisition has been reported at numerous research sites. the chimpanzees of the kibale forest, western uganda, have not previously been observed to use tools in foraging for insects. here i report the first observation of tool use by the chimpanzees of the ngogo community of kibale national park, uganda, in insect foraging. three adult females, one adolescent male, and one juvenile male were observed making and using tools to probe into a fallen dead tree to col ...	2005	15834891
ethnomedicinal and bioactive properties of plants ingested by wild chimpanzees in uganda.	wild chimpanzees eat several plant species claimed by traditional healers to cure diseases. however, the behaviour leading apes to ingest these peculiar species is not clearly understood. some of the items consumed by chimpanzees have low nutritional value, and there is a growing body of evidence suggesting that health might be improved or regulated by such ingestion. observations concerning the diet and the health condition of wild chimpanzees (pan troglodytes schweinfurthii) in the kibale nati ...	2005	15913933
testosterone and energetics in wild chimpanzees (pan troglodytes schweinfurthii).	ovarian function in female hominoids is sensitive to both energy flux and energy balance, resulting in a reduced probability of conception during periods when a successful reproductive outcome is less likely. however, the extent to which energetic factors constrain gonadal function in male hominoids is not clear. we examined the effects of both acute and chronic variation in energy availability on urinary testosterone (t) levels in adult male chimpanzees. acute changes in energy availability, wh ...	2005	15940710
demographic influences on the behavior of chimpanzees.	recent research has revealed substantial diversity in the behavior of wild chimpanzees. understanding the sources of this variation has become a central focus of investigation. while genetic, ecological, and cultural factors are often invoked to explain behavioral variation in chimpanzees, the demographic context is sometimes overlooked as a contributing factor. observations of chimpanzees at ngogo, kibale national park, uganda, reveal that the size and structure of the unit group or community c ...	2006	16283424
bioactive properties of plant species ingested by chimpanzees (pan troglodytes schweinfurthii) in the kibale national park, uganda.	we measured the biological activities of a selected sample (84 crude extracts) of 24 species eaten by wild chimpanzees (pan troglodytes schweinfurthii) in the kibale national park, western uganda, to assess their potential chemotherapeutic values. antibacterial, antimalarial, and/or antileishmania activities were observed in some crude extracts, and five of these extracts showed a significant cytotoxicity against human tumor cells. active compounds isolated from three plant parts occasionally in ...	2006	16419122
lethal intergroup aggression by chimpanzees in kibale national park, uganda.	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 aggressi ...	2006	16429415
intestinal parasite infections and fecal steroid levels in wild chimpanzees.	immune-endocrine interactions have been evaluated much less frequently in nonhuman primates, and this may be due, in part, to logistical and ethical concerns regarding trapping and sampling of endangered species, especially apes. using noninvasive fecal collection methods, the present study evaluates possible relationships between fecal steroid levels and gastrointestinal parasite infections in the ngogo chimpanzee community in kibale national park, uganda. because both testosterone and cortisol ...	2006	16444733
spatial distribution of primates in a mosaic of colonizing and old growth forest at ngogo, kibale national park, uganda.	primate censuses were conducted in a mosaic of colonizing (two locations) and old-growth forests using line transect methods at the ngogo study site, kibale national park, uganda. black and white colobus monkeys (colobus guereza) were encountered more frequently in the colonizing forests than in the old growth forest, while chimpanzees (pan troglodytes) were encountered more frequently in the old growth forest than in colonizing forests. although not significant, results suggest that blue monkey ...	2006	16479411
primate abundance along five transect lines at ngogo, kibale national park, uganda.	using the line transect methods, i studied the primate density at ngogo, kibale national park, uganda for 18 months. comparisons with other studies show that the population of red colobus monkeys (procolobus rufomitratus) and blue monkeys (cercopithecus mitis) is declining, whereas the populations of black-and-white colobus (colobus guereza), red-tailed monkeys (cercopithecus ascanius), grey-cheeked mangabeys (lophocebus albigena), baboons (papio anubis), and chimpanzees (pan troglodytes) remain ...	2007	17330309
taphonomic analysis of skeletal remains from chimpanzee hunts at ngogo, kibale national park, uganda.	this study provides a taphonomic analysis of the largest known sample of bone fragments collected from chimpanzee hunts. the entire sample consists of 455 bone fragments from 57 chimpanzee hunting episodes of 65 prey individuals at ngogo, kibale national park, uganda. it has low taxonomic diversity, consisting overwhelmingly of primates, especially red colobus monkeys. the age distribution of the prey remains is skewed towards pre-adults. cranial bones are the dominant element, followed by long ...	2007	17346774
effects of male group size, parity, and cycle stage on female chimpanzee copulation rates at ngogo, kibale national park, uganda.	chimpanzees have complex and variable mating strategies, but most copulations occur when females with full sexual swellings are in parties with multiple males and mate with most or all of those males. daily copulation rates for fully swollen females vary at different times of a female's cycle, among females, and across communities and populations. variation in female age, parity, and cycle stage underlie some of this variation, but possible demographic effects on copulation rates have not been s ...	2007	17516133
scavenging by chimpanzees at ngogo and the relevance of chimpanzee scavenging to early hominin behavioral ecology.	chimpanzees regularly hunt a variety of prey species. however, they rarely scavenge, which distinguishes chimpanzee carnivory from that of some modern hunter-gatherers and, presumably, at least some plio-pleistocene hominins. i use observations made over an 11-year period to document all known opportunities for scavenging encountered by chimpanzees at ngogo, kibale national park, uganda, and describe all cases of scavenging. i also review data on scavenging from other chimpanzee research sites. ...	2008	17900659
influence of chimpanzee predation on the red colobus population at ngogo, kibale national park, uganda.	frequent hunting of red colobus monkeys (procolobus rufomitratus) takes place at all long-term chimpanzee (pan troglodytes) study sites where both species are present. red colobus are the most commonly selected prey of chimpanzees even when other monkey species are more abundant. in particular, the chimpanzee community at ngogo, kibale national park, uganda, preys heavily on red colobus monkeys: the chimpanzee hunting success rate is extremely high, and chimpanzees kill many individuals per succ ...	2008	17906844
diet and reproductive function in wild female chimpanzees (pan troglodytes schweinfurthii) at kibale national park, uganda.	human female reproductive function is highly sensitive to current energetic condition, indicating adaptation to modulate reproductive effort in accordance with changing ecological conditions that might favor or disfavor the production of offspring. here, we test the hypothesis that reproductive capacity in female chimpanzees is likewise limited by current energetic condition. we used 12 years of data on wild chimpanzees (pan troglodytes schweinfurthii) in the kanyawara community of kibale nation ...	2008	18046778
skeletal pathology in pan troglodytes schweinfurthii in kibale national park, uganda.	the ecological pressures shaping chimpanzee anatomy and behavior are the subject of much discussion in primatology and paleoanthropology, yet empirical data on fundamental parameters including body size, morbidity, and mortality are rare for wild chimpanzees. here, we present skeletal pathology and body size data for 20 (19 crania, 12 postcrania) chimpanzees (pan troglodytes schweinfurthii) from kibale national park, uganda. we compare these data with other east african populations, especially g ...	2008	18067120
geophagy: soil consumption enhances the bioactivities of plants eaten by chimpanzees.	geophagy, the deliberate ingestion of soil, is a widespread practice among animals, including humans. although some cases are well documented, motivations and consequences of this practice on the health status of the consumer remain unclear. in this paper, we focused our study on chimpanzees (pan troglodytes schweinfurthii) of the kibale national park, uganda, after observing they sometimes ingest soil shortly before or after consuming some plant parts such as leaves of trichilia rubescens, whic ...	2008	18188538
specific gravity as an alternative to creatinine for estimating urine concentration in captive and wild chimpanzee (pan troglodytes) samples.	the measurement of hormones in urine has become a widely used technique in primatology. because urine concentration varies according to fluid intake, concentration must be measured in each sample collected, and hormone values are always expressed per unit of concentration. traditionally, creatinine has been used as a concentration index, but some studies in humans have shown that creatinine varies among populations and even within and between individuals within a population, and that it begins t ...	2009	18973242
floristic heterogeneity between forested sites in kibale national park, uganda: insights into the fine-scale determinants of density in a large-bodied frugivorous primate.	1. despite a long history of research on the influence of fruit availability on the population density of large-bodied vertebrate frugivores, operational understanding of the factors regulating density in these taxa remains elusive. we propose that fruit resources can be distinguished from one another on the basis of their functional role for the animals in question, and that such a classification system can aid in identifying the most influential determinants of frugivore density. 2. we compare ...	2009	19523110
nodular worm infection in wild chimpanzees in western uganda: a risk for human health?	this study focused on oeosophagostomum sp., and more especially on o. bifurcum, as a parasite that can be lethal to humans and is widespread among humans and monkeys in endemic regions, but has not yet been documented in apes. its epidemiology and the role played by non-human primates in its transmission are still poorly understood. o. stephanostomum was the only species diagnosed so far in chimpanzees. until recently, o. bifurcum was assumed to have a high zoonotic potential, but recent finding ...	2010	20300510