Pan Troglodytes Schweinfurthii Research Articles

AVPR1A Variation in Chimpanzees (Pan troglodytes): Population Differences and Association with Behavioral Style

Primates and other mammals show measurable, heritable variation in behavioral traits such as gregariousness, timidity, and aggression. Connections among behavior, environment, neuroanatomy, and genetics are complex, but small genetic differences can have large effects on behavioral phenotypes. One of the best examples of a single gene with large effects on natural variation in social behavior is AVPR1A, which codes for a receptor of the peptide hormone arginine vasopressin. Work on rodents shows a likely causal association between AVPR1A regulatory polymorphisms and social behavior. Chimpanzees also show variation in the AVPR1A regulatory region, with some individuals lacking a ca. 350-bp segment corresponding to a putative functional element. Thus, chimpanzees have a “short” allele (segment deletion) and a “long” allele (no deletion) at this locus. Here we compare AVPR1A variation in two chimpanzee populations, and we examine behavioral and hormonal data in relation to AVPR1A genotypes. We genotyped AVPR1A in a captive population of western chimpanzees (Pan troglodytes verus, New Iberia Research Center; N = 64) for which we had quantitative measures of personality (based on 15 behavioral style indices, calculated from 3 yr of observational data), dominance rank, and baseline testosterone levels. We also provide the first assessment of AVPR1A genotype frequencies in a wild eastern chimpanzee population (Pan troglodytes schweinfurthii, Ngogo community, Kibale National Park, Uganda; N = 26). Our results indicated that the AVPR1A long allele was associated with a “smart” social personality in captive western chimpanzees, independent of testosterone levels. Although the frequency of the long allele was relatively low in captive western chimpanzees (0.23), it was the major allele in wild eastern chimpanzees (0.62). Our finding that allele and genotype frequencies for the AVPR1A polymorphism differ among chimpanzee populations also highlights the need for comparative studies —across subspecies and research sites— in primate behavioral genetics.

Genetic diversity at the edge: comparative assessment of Y-chromosome and autosomal diversity in eastern chimpanzees (Pan troglodytes schweinfurthii) of Ugalla, Tanzania

One of the three categories of biodiversity for conservation priority recommended by the International Union for the Conservation of Nature is genetic diversity. In this study, we estimate the genetic diversity of eastern chimpanzees in the Ugalla region of western Tanzania, which represents the easternmost distribution of the subspecies Pan troglodytes schweinfurthii. We collected 237 fecal samples from a 624 km2 area of the Ugalla region, analyzed the DNA at 12 autosomal loci and identified 113 individuals (69 males and 44 females). We also analyzed 13 Y-chromosome loci in the Ugalla males. While autosomal genetic diversity is within the range of other eastern populations, at 0.27 the gene diversity of the Y-chromosome haplotypes present among 61 Ugalla males is extremely low as compared to other eastern chimpanzee populations. In addition, the most prevalent haplotype, found in 52 of the males, is distributed across the entire surveyed area of 624 km2. This low level of paternally-transmitted genetic diversity among the Ugalla males may be the result of a small or highly related, recent founder population (i.e., genetic drift), exacerbated by the male philopatric structure of chimpanzee communities and by male reproductive skew.

<Article> Chimpanzee (Pan troglodytes schweinfurthii) Population Density and Abundance in Kibira National Park, Burundi

The eastern chimpanzee, Pan troglodytes schweinfurthii, is an endangered chimpanzee subspecies of global conservation concern, living at low density (less than 1 individual/km 2 ) in most of its range (Keele et al. 2006; Plumptre et al. 2011) in eastern Africa. As chimpanzees have a relatively low reproductive rate (Caldecott & Miles 2009), their ability to recover from population decline is limited. Documenting the extent and severity of such decline events, as well as targeting adequate conservation plans, requires reliable baseline data on density estimates of great apes (Oates 1996) in area of occurrence.

Contrasting demographic histories of the neighboring bonobo and chimpanzee

The Pleistocene epoch was a period of dramatic climate change that had profound impacts on the population sizes of many animal species. How these species were shaped by past events is often unclear, hindering our understanding of the population dynamics resulting in present day populations. We analyzed complete mitochondrial genomes representing all four recognized chimpanzee subspecies and the bonobo to infer the recent demographic history and used simulations to exclude a confounding effect of population structure. Our genus-wide Bayesian coalescent-based analysis revealed surprisingly dissimilar demographic histories of the chimpanzee subspecies and the bonobo, despite their overlapping habitat requirements. Whereas the central and eastern chimpanzee subspecies were inferred to have expanded tenfold between around 50,000 and 80,000 years ago and today, the population size of the neighboring bonobo remained constant. The changes in population size are likely linked to changes in habitat area due to climate oscillations during the late Pleistocene. Furthermore, the timing of population expansion for the rainforest-adapted chimpanzee is concurrent with the expansion of the savanna-adapted human, which could suggest a common response to changed climate conditions around 50,000-80,000 years ago.

Impact of Humans on Long-Distance Communication Behaviour of Eastern Chimpanzees (Pan troglodytes schweinfurthii) in the Northern Democratic Republic of the Congo

We systematically recorded all long-distance chimpanzee vocalizations and tree drums over a 26-month study period in 13 forest regions in the Democratic Republic of the Congo. We found that the frequency of chimpanzee vocalizations and tree drums was considerably higher in the remote Gangu Forest than in other forest regions closer to human settlements and roads. We present evidence indicating that chimpanzees may reduce their levels of vocalizations in areas characterized by high levels of human hunting. The chimpanzees appear to have the behavioural flexibility necessary to modify their behaviour in areas where humans are a major threat. We discuss the possible consequences of this reduction in vocalization rate on the social system of the chimpanzees.

The transmembrane domain of HIV-1 Vpu is sufficient to confer anti-tetherin activity to SIVcpz and SIVgor Vpu proteins: cytoplasmic determinants of Vpu function

BackgroundThe acquisition of effective Vpu-mediated anti-tetherin activity to promote virion release following transmission of SIVcpzPtt from central chimpanzees (Pan troglodytes troglodytes) to humans distinguishes pandemic HIV-1 group M strains from non-pandemic group N, O and P viruses and may have been a prerequisite for their global spread. Some functional motifs in the cytoplasmic region of HIV-1 M Vpus proposed to be important for anti-tetherin activity are more frequently found in the Vpu proteins of SIVcpzPtt than in those of SIVcpzPts infecting eastern chimpanzees (P. t. schweinfurthii), that have not been detected in humans, and SIVgor from gorillas, which is closely related to HIV-1 O and P. Thus, SIVcpzPtt strains may require fewer adaptive changes in Vpu than SIVcpzPts or SIVgor strains to counteract human tetherin.ResultsTo examine whether SIVcpzPtt may only need changes in the transmembrane domain (TMD) of Vpu to acquire anti-tetherin activity, whereas SIVcpzPts and SIVgor may also require changes in the cytoplasmic region, we analyzed chimeras between the TMD of an HIV-1 M Vpu and the cytoplasmic domains of SIVcpzPtt (n = 2), SIVcpzPts (n = 2) and SIVgor (n = 2) Vpu proteins. Unexpectedly, all of these chimeras were capable of counteracting human tetherin to enhance virion release, irrespective of the presence or absence of the putative adaptor protein binding sites and the DSGxxS β-TrCP binding motif reported to be critical for effective anti-tetherin activity of M Vpus. It was also surprising that in three of the six chimeras the gain of anti-tetherin function was associated with a loss of the CD4 degradation activity since this function was conserved among all parental HIV-1, SIVcpz and SIVgor Vpu proteins.ConclusionsOur results show that changes in the TMD of SIVcpzPtt, SIVcpzPts and SIVgor Vpus are sufficient to render them active against human tetherin. Thus, several previously described domains in the extracellular region of Vpu are not absolutely essential for tetherin antagonism but may be required for other Vpu functions.

Gene Flow and Genetic Diversity of Chimpanzees in Tanzanian Habitats

Abstract: Tanzania is located at the southeastern end of the eastern chimpanzee (Pan troglodytes schweinfurthii) distribution. Except for two national parks, their habitats have been degraded due to human activities. To clarify the gene flow and genetic diversity of chimpanzees in Tanzania, we analyzed the mitochondrial sequences of chimpanzees in six sites (Lwazi, Wansisi, Mahale, Karobwa, Ugalla-Masito, and Gombe), some of which are now isolated. The southernmost habitat (Lwazi) was about 150 km away from the nearest habitat but, considering the geographic distance, the genetic distance of the chimpanzees between Lwazi and the other habitats was not high. In contrast, the genetic distance between the chimpanzees in the northernmost habitat (Gombe), and the other habitats was relatively high considering the geographic distance. The results suggest that the Malagarasi River, which runs between Gombe and the southern habitats, limits gene flow. The genetic difference analyses also suggest that the habitats...

Chimpanzees in mantraps: lethal crop protection and conservation in Uganda

AbstractA main concern of farmers worldwide is how to reduce crop losses to wildlife. Some potentially lethal crop protection methods are non-selective. It is important to understand the impact of such methods on species of conservation concern. Uganda has important populations of Endangered eastern chimpanzeesPan troglodytes schweinfurthii. Farmers sometimes use large metal mantraps to guard their fields against crop-raiding wildlife, particularly baboonsPapio anubisand wild pigsPotamochoerussp.. Chimpanzees that range onto farmland also step in these illegal devices and without rapid veterinary invention face severe injury or eventual death. Unlike inadvertent snaring of great apes in African forests, the problem of mantraps in forest–farm ecotones has received little attention. We report 10 cases of entrapped chimpanzees in the cultivated landscape surrounding Uganda's Budongo Forest during 2007–2011, undoubtedly only a portion of the actual number of cases. Mantraps currently present a substantial threat to ape populations in this important conservation landscape. Our data underscore the need for conservation programmes to consider the techniques used by rural farmers to protect their livelihoods from wild animals.

Recent decline in suitable environmental conditions for African great apes

AbstractAimTo predict the distribution of suitable environmental conditions (SEC) for eight African great ape taxa for a first time period, the 1990s and then project it to a second time period, the 2000s; to assess the relative importance of factors influencing SEC distribution and to estimate rates of SEC loss, isolation and fragmentation over the last two decades.LocationTwenty‐two African great ape range countries.MethodsWe extracted 15,051 presence localities collected between 1995 and 2010 from 68 different areas surveyed across the African ape range. We combined a maximum entropy algorithm and logistic regression to relate ape presence information to environmental and human impact variables from the 1990s with a resolution of 5 × 5 km across the entire ape range. We then made SEC projections for the 2000s using updated human impact variables.ResultsTotal SEC area was approximately 2,015,480 and 1,807,653 km2 in the 1990s and 2000s, respectively. Loss of predicted SEC appeared highest for Cross River gorillas (−59%), followed by eastern gorillas (−52%), western gorillas (−32%), bonobos (−29%), central chimpanzees (−17%) and western chimpanzees (−11%). SEC for Nigeria‐Cameroon chimpanzees and eastern chimpanzees was not greatly reduced. Except for Cross River and eastern gorillas, the number of SEC patches did not change significantly, suggesting that SEC loss was caused mainly by patch size reduction.Main conclusionsThe first continent‐wide perspective of African ape SEC distribution shows dramatic declines in recent years. The model has clear limitations for use at small geographic scales, given the quality of available data and the coarse resolution of predictions. However, at the large scale it has potential for informing international policymaking, mitigation of resource extraction and infrastructure development, as well as for spatial prioritization of conservation effort and evaluating conservation effectiveness.

Eco-geographical diversification of bitter taste receptor genes (TAS2Rs) among subspecies of chimpanzees (Pan troglodytes).

Chimpanzees (Pan troglodytes) have region-specific difference in dietary repertoires from East to West across tropical Africa. Such differences may result from different genetic backgrounds in addition to cultural variations. We analyzed the sequences of all bitter taste receptor genes (cTAS2Rs) in a total of 59 chimpanzees, including 4 putative subspecies. We identified genetic variations including single-nucleotide variations (SNVs), insertions and deletions (indels), gene-conversion variations, and copy-number variations (CNVs) in cTAS2Rs. Approximately two-thirds of all cTAS2R haplotypes in the amino acid sequence were unique to each subspecies. We analyzed the evolutionary backgrounds of natural selection behind such diversification. Our previous study concluded that diversification of cTAS2Rs in western chimpanzees (P. t. verus) may have resulted from balancing selection. In contrast, the present study found that purifying selection dominates as the evolutionary form of diversification of the so-called human cluster of cTAS2Rs in eastern chimpanzees (P. t. schweinfurthii) and that the other cTAS2Rs were under no obvious selection as a whole. Such marked diversification of cTAS2Rs with different evolutionary backgrounds among subspecies of chimpanzees probably reflects their subspecies-specific dietary repertoires.

Eastern Chimpanzees, but Not Bonobos, Represent a Simian Immunodeficiency Virus Reservoir

Chimpanzees in west central Africa (Pan troglodytes troglodytes) are endemically infected with simian immunodeficiency viruses (SIVcpzPtt) that have crossed the species barrier to humans and gorillas on at least five occasions, generating pandemic and nonpandemic forms of human immunodeficiency virus type 1 (HIV-1) as well as gorilla SIV (SIVgor). Chimpanzees in east Africa (Pan troglodytes schweinfurthii) are also infected with SIVcpz; however, their viruses (SIVcpzPts) have never been found in humans. To examine whether this is due to a paucity of natural infections, we used noninvasive methods to screen wild-living eastern chimpanzees in the Democratic Republic of the Congo (DRC), Uganda, and Rwanda. We also screened bonobos (Pan paniscus) in the DRC, a species not previously tested for SIV in the wild. Fecal samples (n = 3,108) were collected at 50 field sites, tested for species and subspecies origin, and screened for SIVcpz antibodies and nucleic acids. Of 2,565 samples from eastern chimpanzees, 323 were antibody positive and 92 contained viral RNA. The antibody-positive samples represented 76 individuals from 19 field sites, all sampled north of the Congo River in an area spanning 250,000 km(2). In this region, SIVcpzPts was common and widespread, with seven field sites exhibiting infection rates of 30% or greater. The overall prevalence of SIVcpzPts infection was 13.4% (95% confidence interval, 10.7% to 16.5%). In contrast, none of the 543 bonobo samples from six sites was antibody positive. All newly identified SIVcpzPts strains clustered in strict accordance to their subspecies origin; however, they exhibited considerable genetic diversity, especially in protein domains known to be under strong host selection pressure. Thus, the absence of SIVcpzPts zoonoses cannot be explained by an insufficient primate reservoir. Instead, greater adaptive hurdles may have prevented the successful colonization of humans by P. t. schweinfurthii viruses.

Application of McMaster's technique in live blue whales

Knowledge of cetacean parasites has been obtained from harvested and stranded animals; however, the information obtained from dead animals cannot be considered representative of the ‘normal’ population (Wobeser 1994). Due...

Reactions of Bili‐Uele Chimpanzees to Humans in Relation to Their Distance From Roads and Villages

In order to assess the impact of human activities on chimpanzee behavior, we compared reactions to humans of Eastern chimpanzees (Pan troglodytes schweinfurthii) living in proximity to and at a distance from roads and settlements in the Bili-Uele landscape in Northern Democratic Republic of the Congo (DRC). We found that chimpanzees in the remote Gangu Forest were more likely to show curious or neutral reactions to us and were less likely to flee than those living closer to roads. In addition, arboreal contact durations with Gangu chimpanzees lasted significantly longer than elsewhere. The most likely explanation for this phenomenon is that with increasing distance from roads, chimpanzees have in the recent past had fewer negative encounters with humans, and thus never learned to fear them. The discovery of this population of "naïve chimpanzees" presents us with an important research and conservation opportunity that may result in the installation of a long-term research site and increased protection of the population.

Genetic Sampling of Unhabituated Chimpanzees (Pan troglodytes schweinfurthii) in Gishwati Forest Reserve, an Isolated Forest Fragment in Western Rwanda

Many primate populations currently live in forest fragments. These populations are often unhabituated, elusive, and contain few individuals, making them difficult to study through direct observation. Noninvasive genetic methods are useful for surveying these unhabituated populations to infer the number and sex of individuals and the genetic diversity of the population. We conducted genetic analysis on 70 fecal samples from eastern chimpanzees (Pan troglodytes schweinfurthii) in Gishwati Forest Reserve, a forest fragment in western Rwanda. We genotyped all but two of these samples using 12 autosomal and 13 Y-chromosome microsatellite markers previously used in analyses of other chimpanzee populations. The genetic data show that these samples represent a minimum of 19 individuals (7 females, 12 males). However, because we may not have sampled all individuals in the population, we also performed mark-recapture analysis with the genetic data and found that the entire population likely numbers between 19 and 29 individuals. These results are consistent with opportunistic observations of at least 19 individual chimpanzees. Levels of variation at the Y-chromosome microsatellites were similar to those observed in other chimpanzee communities, suggesting that the chimpanzees in this forest are members of a single community. These results provide a baseline count of the number of male and female chimpanzees in the Gishwati Forest Reserve, and the data provide the potential for follow-up studies aimed at tracking individuals over time, thus aiding conservation management of this unhabituated population.

Dentoalveolar abscess variation among three groups of chimpanzees (Pan troglodytes schweinfurthii, Pan troglodytes troglodytes, and Pan paniscus)

The prevalence and pattern of periodontal and periapical dental abscess lesions are examined in 399 wild caught chimpanzee mandibles and maxillae from museum contexts (138 Pan troglodytes troglodytes, 152 Pan troglodytes schweinfurthii and 109 Pan paniscus). This study tests two predictions. First, canine size is the key determining factor in dental abscesses. Second, tooth breakage leads to higher frequencies of abscesses. Abscess frequencies were calculated for adult males (P. t. troglodytes 14.6%, P. t. schweinfurthii 16.3%, P. paniscus 15.4%) and females (P. t. troglodytes 15.7%, P. t. schweinfurthii 6.7%, P. paniscus 10.3%), while attempting to control for dental attrition. No significant differences were found in the occurrence of abscesses among the sexes or species examined. This finding suggests that males and females are subjected to the same risks for dental abscesses, which are likely related to dental attrition rather than breakage.

High prevalence of simian immunodeficiency virus infection in a community of savanna chimpanzees.

Simian immunodeficiency virus of chimpanzees (SIVcpz) has a significant negative impact on the health, reproduction, and life span of chimpanzees, yet the prevalence and distribution of this virus in wild-living populations are still only poorly understood. Here, we show that savanna chimpanzees, who live in ecologically marginal habitats at 10- to 50-fold lower population densities than forest chimpanzees, can be infected with SIVcpz at high prevalence rates. Fecal samples were collected from nonhabituated eastern chimpanzees (Pan troglodytes schweinfurthii) in the Issa Valley (n = 375) and Shangwa River (n = 6) areas of the Masito-Ugalla region in western Tanzania, genotyped to determine the number of sampled individuals, and tested for SIVcpz-specific antibodies and nucleic acids. None of 5 Shangwa River apes tested positive for SIVcpz; however, 21 of 67 Issa Valley chimpanzees were SIVcpz infected, indicating a prevalence rate of 31% (95% confidence interval, 21% to 44%). Two individuals became infected during the 14-month observation period, documenting continuing virus spread in this community. To characterize the newly identified SIVcpz strains, partial and full-length viral sequences were amplified from fecal RNA of 10 infected chimpanzees. Phylogenetic analyses showed that the Ugalla viruses formed a monophyletic lineage most closely related to viruses endemic in Gombe National Park, also located in Tanzania, indicating a connection between these now separated communities at some time in the past. These findings document that SIVcpz is more widespread in Tanzania than previously thought and that even very low-density chimpanzee populations can be infected with SIVcpz at high prevalence rates. Determining whether savanna chimpanzees, who face much more extreme environmental conditions than forest chimpanzees, are more susceptible to SIVcpz-associated morbidity and mortality will have important scientific and conservation implications.

Male-Mediated Gene Flow in Patrilocal Primates

BackgroundMany group–living species display strong sex biases in dispersal tendencies. However, gene flow mediated by apparently philopatric sex may still occur and potentially alters population structure. In our closest living evolutionary relatives, dispersal of adult males seems to be precluded by high levels of territoriality between males of different groups in chimpanzees, and has only been observed once in bonobos. Still, male–mediated gene flow might occur through rare events such as extra–group matings leading to extra–group paternity (EGP) and female secondary dispersal with offspring, but the extent of this gene flow has not yet been assessed.Methodology/Principal FindingsUsing autosomal microsatellite genotyping of samples from multiple groups of wild western chimpanzees (Pan troglodytes verus) and bonobos (Pan paniscus), we found low genetic differentiation among groups for both males and females. Characterization of Y–chromosome microsatellites revealed levels of genetic differentiation between groups in bonobos almost as high as those reported previously in eastern chimpanzees, but lower levels of differentiation in western chimpanzees. By using simulations to evaluate the patterns of Y–chromosomal variation expected under realistic assumptions of group size, mutation rate and reproductive skew, we demonstrate that the observed presence of multiple and highly divergent Y–haplotypes within western chimpanzee and bonobo groups is best explained by successful male–mediated gene flow.Conclusions/SignificanceThe similarity of inferred rates of male–mediated gene flow and published rates of EGP in western chimpanzees suggests this is the most likely mechanism of male–mediated gene flow in this subspecies. In bonobos more data are needed to refine the estimated rate of gene flow. Our findings suggest that dispersal patterns in these closely related species, and particularly for the chimpanzee subspecies, are more variable than previously appreciated. This is consistent with growing recognition of extensive behavioral variation in chimpanzees and bonobos.

Status and conservation of the only population of the Vulnerable owl-faced monkey Cercopithecus hamlyni in Rwanda

AbstractThe elusive, Vulnerable owl-faced monkey Cercopithecus hamlyni is a rare and little studied species and one of the least known of the African Cercopithecidae. This study describes the distribution and relative abundance of the only known population in East Africa, in Nyungwe National Park, Rwanda. This species is restricted to a small (32 km2) area of bamboo and bamboo–forest mix in the southern sector of the Park, close to the international border with Burundi. We present the first empirical data of its abundance in the bamboo forests of Nyungwe. A total length of 185 km of transect were surveyed to estimate relative abundance of diurnal primates. Encounter rates with the owl-faced monkey were 0.081 groups km-1 (n = 15). Mean group size was 3.6 individuals. Eight independent photographs of C. hamlyni were obtained from five camera traps during 182 camera-days. Four other species of primates occur in the bamboo forest: eastern chimpanzee Pan troglodytes schweinfurthii, Angola colobus Colobus angolensis, L’Hoest’s monkey Cercopithecus l’hoesti and blue monkey Cercopithecus mitis. The main threats to the bamboo forest are from the illegal harvesting of bamboo, trapping and tree-cutting. These threats originate from both Rwanda and Burundi. There is an urgent need for conservation action to halt the destruction and degradation of the bamboo forest and to ensure the long-term survival of the owl-faced monkey in Rwanda.

Insectivory of savanna chimpanzees (Pan troglodytes verus) at Fongoli, Senegal

Little is known about the behavior of chimpanzees living in savanna-woodlands, although they are of particular interest to anthropologists for the insight they can provide regarding the ecological pressures affecting early hominins living in similar habitats. Fongoli, Senegal, is the first site where savanna chimpanzees have been habituated for observational data collection and is the hottest and driest site where such observation of chimpanzees occurs today. Previously, indirect evidence suggested these chimpanzees consumed termites throughout the year, an unusual occurrence for western and eastern chimpanzees. Although meat eating by chimpanzees continues to receive much attention, their use of invertebrate prey has received less emphasis in scenarios of hominin evolution. Here, we further examine the invertebrate diet of Fongoli chimpanzees using direct observational methods and accounting for potential environmental influences. Termite feeding positively correlated with high temperatures. Fongoli chimpanzees spend more time obtaining termites than any other chimpanzee population studied, and this extensive insectivory contributes to the list of distinctive behaviors they display relative to chimpanzees living in more forested habitats. We suggest that savanna chimpanzees at Fongoli differ significantly from chimpanzees elsewhere as a result of the selective pressures characterizing their harsh environment, and this contrast provides an example of a viable referential model for better understanding human evolution. Specifically, our results support the hypotheses that invertebrate prey may have figured more prominently into the diet of early hominins in similar habitats, especially given that invertebrates are an important source of protein and other essential nutrients in a highly seasonal environment.

Demographic and ecological effects on patterns of parasitism in eastern chimpanzees (Pan troglodytes schweinfurthii) in Gombe National Park, Tanzania.

From January 2006 to January 2008, we collected 1,045 fecal samples from 90 individually-recognized, free-ranging, eastern chimpanzees (Pan troglodytes schweinfurthii) inhabiting Gombe National Park, Tanzania to determine how patterns of parasitism are affected by demographic and ecological covariates. Seventeen parasite species were recovered, including eight nematodes (Oesophagostomum sp., Necator sp., Probstmayria gombensis, Strongyloides fulleborni, Ascaris sp., Trichuris sp., Abbreviata caucasica, and an unidentified strongyle), 1 cestode (Bertiella sp.), 1 trematode (Dicrocoeliidae), and 7 protozoa (Entamoeba coli, Entamoeba histolytica/dispar, Iodamoeba bütschlii, Troglodytella abrassarti, Troglocorys cava, Balantidium coli, and an unidentified protozoa). Significant differences were observed in interannual infection prevalence and parasite richness between 2006 and 2007. Intercommunity comparisons demonstrated higher prevalence of parasites for the Mitumba compared with Kasekela chimpanzee community. Prevalence of several parasites was strongly correlated with monthly rainfall patterns for both 2006 and 2007. Subadult chimpanzees had lower prevalence for most parasite species compared with adults in both years and also yielded a lower average parasite species richness. No significant differences were observed between males and females in prevalence in 2006. However, in 2007 the prevalence of S. fulleborni and I. bütschlii were higher in males than in females. Parasite prevalence and richness were substantially higher in this multiyear study compared with previous short-term studies of the gastrointestinal parasites of Gombe chimpanzees. This coupled with the significant interannual and interseasonal variation, demonstrated in this study, emphasizes the importance of multiyear monitoring with adequate sample size to effectively determine patterns of parasitism in wild primate populations.