| idiopathic myocardial fibrosis in captive chimpanzees (pan troglodytes). | cardiovascular disorders and predominantly idiopathic myocardial fibrosis are frequently associated with mortality among zoo-housed chimpanzees (pan troglodytes). formalin-fixed whole hearts of deceased chimpanzees housed in zoos (n = 33) and an african sanctuary (n = 2) underwent detailed macroscopic and histopathologic examination using a standardized protocol. archived histological slides from the hearts of 23 additional african sanctuary-housed chimpanzees were also examined. myocardial fibr ... | 2020 | 31640487 |
| basicranial ontogeny comparison in pan troglodytes and homo sapiens and its use for developmental stage definition of knm-er 42700. | this study aims to develop a comparative basis for assessing the developmental stage of knm-er 42700 based on the ontogenetic pattern of the ectocranial surface of the basicranium in modern humans and chimpanzees. | 2019 | 31633198 |
| novel y-chromosome long non-coding rnas expressed in human male cns during early development. | global microarray gene expression analyses previously demonstrated differences in female and male embryos during neurodevelopment. in particular, before sexual maturation of the gonads, the differences seem to concentrate on the expression of genes encoded on the x- and y-chromosomes. to investigate genome-wide differences in expression during this early developmental window, we combined high-resolution rna sequencing with qpcr to analyze brain samples from human embryos during the first trimest ... | 2019 | 31608120 |
| the cochlea of the sima de los huesos hominins (sierra de atapuerca, spain): new insights into cochlear evolution in the genus homo. | the cochlea contains taxonomic and phylogenetic information and its morphology is related with hearing abilities among fossil hominins. data for the genus homo is presently limited to early homo and the early neandertals from krapina. the present study of the middle pleistocene hominins from the sima de los huesos (sh) provides new evidence on cochlear evolution in the genus homo. we compared the absolute length, proportional lengths of each turn, number of turns, size and shape of the cross-sec ... | 2019 | 31569005 |
| social relationships and greetings in wild chimpanzees (pan troglodytes): use of signal combinations. | signals of submission, so-called 'greetings', represent an important tool for the regulation of social life in primates. in chimpanzees, vocalizations and gestures are commonly employed to communicate greetings, however, the topic of signal complexity (i.e., combinations of signals) during greeting instances has been neglected by research to date. here, we investigate combinatorial possibilities in vocal greetings in a free-ranging group of chimpanzees (pan troglodytes) and study how greeter sex ... | 2019 | 31552566 |
| chimpanzees use observed temporal directionality to learn novel causal relations. | we investigated whether chimpanzees use the temporal sequence of external events to determine causation. seventeen chimpanzees (pan troglodytes) witnessed a human experimenter press a button in two different conditions. when she pressed the "causal button" the delivery of juice and a sound immediately followed (cause-then-effect). in contrast, she pressed the "non-causal button" only after the delivery of juice and sound (effect-then-cause). when given the opportunity to produce the desired juic ... | 2019 | 31549268 |
| how chimpanzees (pan troglodytes) share the spoils with collaborators and bystanders. | chimpanzees hunt cooperatively in the wild, but the factors influencing food sharing after the hunt are not well understood. in an experimental study, groups of three captive chimpanzees obtained a monopolizable food resource, either via two individuals cooperating (with the third as bystander) or via one individual acting alone alongside two bystanders. the individual that obtained the resource first retained most of the food but the other two individuals attempted to obtain food from the "capt ... | 2019 | 31545837 |
| density and distribution of western chimpanzees around a bauxite deposit in the boé sector, guinea-bissau. | the boé sector in southeast guinea-bissau harbors a population of western chimpanzees (pan troglodytes verus) that inhabits a mosaic of forest and savanna. the boé sector contains a substantial bauxite deposit in a region called ronde hill, and there are plans for the construction of a mine, which may endanger the chimpanzee population. in 1-week survey in may 2013, we used the standing crop nest counts method to obtain the number of chimpanzee nests and from that estimate the density and abunda ... | 2019 | 31520454 |
| observational data reveal evidence and parameters of contagious yawning in the behavioral repertoire of captive-reared chimpanzees (pan troglodytes). | there is robust experimental evidence for contagious yawning, yet observational studies of naturalistic behavior have been fewer. without data from real-world behavior, researchers have questioned the existence of contagious yawning and made assumptions about some parameters (e.g., the duration of the effect). we observed contagious yawning in chimpanzees to confirm/disconfirm its existence in the behavioral repertoire of this species, and if present, provide some of the missing descriptives. we ... | 2019 | 31519942 |
| do chimpanzees (pan troglodytes) console a bereaved mother? | comparative thanatology encompasses the study of death-related responses in non-human animals and aspires to elucidate the evolutionary origins of human behavior in the context of death. many reports have revealed that humans are not the only species affected by the death of group members. non-human primates in particular show behaviors such as congregating around the deceased, carrying the corpse for prolonged periods of time (predominantly mothers carrying dead infants), and inspecting the cor ... | 2020 | 31485897 |
| towards systematic and evidence-based conservation planning for western chimpanzees. | as animal populations continue to decline, frequently driven by large-scale land-use change, there is a critical need for improved environmental planning. while data-driven spatial planning is widely applied in conservation, as of yet it is rarely used for primates. the western chimpanzee (pan troglodytes verus) declined by 80% within 24 years and was uplisted to critically endangered by the iucn red list of threatened species in 2016. to support conservation planning for western chimpanzees, we ... | 2019 | 31468565 |
| the psychological mechanisms underlying reciprocal prosociality in chimpanzees (pan troglodytes). | in both the wild and captivity, chimpanzees engage in reciprocal patterns of prosocial behavior. however, the proximate mechanisms underlying these patterns are unclear. in the current study, we investigated whether chimpanzees prefer to act prosocially toward conspecifics who have directly benefited them (perhaps based on an affective bond) or whether they simply observe the prosocial behavior of others in general (including indirectly to third parties) and preferentially interact with and beha ... | 2020 | 31464454 |
| exploring interactions between blastocystis sp., strongyloides spp. and the gut microbiomes of wild chimpanzees in senegal. | gut parasites exert an important influence on the gut microbiome, with many studies focusing on the human gut microbiome. it has, however, undergone severe richness depletion. hygienic lifestyle, antimicrobial treatments and altered gut homeostasis (e.g., chronic inflammation) reduce gut microbiome richness and also parasite prevalence; which may confound results. studying species closely related to humans could help overcome this problem by providing insights into the ancestral relationship bet ... | 2019 | 31442596 |
| optional-switch cognitive flexibility in primates: chimpanzees' (pan troglodytes) intermediate susceptibility to cognitive set. | within human problem-solving, the propensity to use a familiar approach, rather than switch to a more efficient alternative is pervasive. this susceptibility to "cognitive set" prevents optimization by biasing response patterns toward known solutions. in a recent study, which used a nonverbal touch screen task, baboons exhibited a striking ability to deviate from their learned strategy to use a more efficient shortcut. humans, on the other hand, displayed the opposite response pattern and almost ... | 2020 | 31424232 |
| short and long-term temporal consistency of hand preference in sanctuary chimpanzees (pan troglodytes) for unimanual and bimanual coordinated tasks. | longitudinal research on manual preferences in humans and non-human primates has mainly been conducted from a developmental perspective, with only a few studies exploring long-term stability of this trait during adulthood. therefore, we investigated short-term (1 year) and long-term (10 and 11 years) consistency of hand preference in a naturalistic group of 19 juvenile and adult chimpanzees (pan troglodytes) by using two experimental tasks, one unimanual (simple reaching) and one bimanual (tube ... | 2019 | 31374226 |
| travel linearity and speed of human foragers and chimpanzees during their daily search for food in tropical rainforests. | to understand the evolutionary roots of human spatial cognition, researchers have compared spatial abilities of humans and one of our closest living relatives, the chimpanzee (pan troglodytes). however, how humans and chimpanzees compare in solving spatial tasks during real-world foraging is unclear to date, as measuring such spatial abilities in natural habitats is challenging. here we compared spatial movement patterns of the mbendjele bayaka people and the taï chimpanzees during their daily s ... | 2019 | 31363113 |
| opportunistic feeding strategy in wild immature chimpanzees: implications for children as active foragers in human evolution. | modern human (homo sapiens) children are generally considered to be dependent on older individuals for foods, even after weaning. however, recent studies of hunter-gatherer societies have reported that children can also acquire food by themselves, although the degree of self-provisioning by children differs among groups and is considered a facultative adaptation. to investigate the dependence of children on older individuals for food and the importance of self-provisioning in early hominins, i e ... | 2019 | 31358176 |
| the development of communication in alarm contexts in wild chimpanzees. | animals have evolved a range of communicative behaviours in the presence of danger. although the mechanisms and functions of some of these behaviours have been relatively well researched, comparatively little is known about their ontogeny, including how animals learn to inform social partners about impending danger. in adult chimpanzees, behaviours in response to dangers involve several channels, particularly alarm calls and simultaneous gaze alternations with nearby recipients. gaze alternation ... | 2019 | 31346303 |
| chimpanzees flexibly update working memory contents and show susceptibility to distraction in the self-ordered search task. | working memory (wm) is a core executive function that allows individuals to hold, process and manipulate information. wm capacity has been repeatedly nominated as a key factor in human cognitive evolution; nevertheless, little is known about the wm abilities of our closest primate relatives. in this study, we examined signatures of wm ability in chimpanzees (pan troglodytes). standard wm tasks for humans (homo sapiens) often require participants to continuously update their wm. in experiment 1, ... | 2019 | 31337315 |
| responses to dead and dying conspecifics and heterospecifics by wild mountain gorillas (gorilla beringei beringei) and chimpanzees (pan troglodytes schweinfurthii). | comparative ["evolutionary")] thanatology is devoted to investigating how animals respond to signs of death and dying, in conspecifics and other species. responses to corpses often involve fear and confusion, and "deceased infant carrying" by females is widespread in nonhuman primates. such behavior could result from "animacy detection malfunctions" (gonçalves and biro in philos trans r soc (b) 373:20170263, 2018): corpses have attributes of animate agents, but-like objects-they do not act, but ... | 2020 | 31278498 |
| further evidence of a left hemisphere specialization and genetic basis for tool use skill in chimpanzees (pan troglodytes): reproducibility in two genetically isolated populations of apes. | it has been hypothesized that the evolution of tool use may have served as a preadaptation for the emergence of left hemispheric specialization in motor skill in humans. here, we tested for intermanual differences in performance on a tool use task in a sample of 206 captive chimpanzees in relation to their sex, age, and hand preference. in addition, we examined heritability in tool use skill for the entire sample, as well as within 2 genetically isolated populations of captive chimpanzees. this ... | 2019 | 31246047 |
| chimpanzees rarely settle on consistent patterns of play in the hawk dove, assurance, and prisoner's dilemma games, in a token exchange task. | games derived from experimental economics can be used to directly compare decision-making behavior across primate species, including humans. for example, the use of coordination games, such as the assurance game, has shown that a variety of primate species can coordinate; however, the mechanism by which they do so appears to differ across species. recently, these games have been extended to explore anti-coordination and cooperation in monkeys, with evidence that they play the nash equilibria in ... | 2019 | 31245532 |
| refinements to captive chimpanzee (pan troglodytes) care: a self-medication paradigm. | in an effort to enhance welfare, behavioural management continually refines methods of non-human primate (nhp) care. chimpanzees (pan troglodytes) are one of the most cognitively complex captive nhps and they have been observed to self-medicate in the wild. the population of captive chimpanzees in the us is aged (due to a breeding moratorium instituted in 1998) and will progressively require more medical care as they get older. to functionally simulate natural self-medication behaviour, provide ... | 2018 | 31244511 |
| relationships between captive chimpanzee (pan troglodytes) welfare and voluntary participation in behavioural studies. | voluntary participation in behavioural studies offers several scientific, management, and welfare benefits to non-human primates (nhps). aside from the scientific benefit of increased understanding of nhp cognition, sociality, and behaviour derived from noninvasive behavioural studies, participation itself has the potential to provide functional simulations of natural behaviours, enrichment opportunities, and increased control over the captive environment, all of which enhance welfare. despite a ... | 2019 | 31244501 |
| maternal influence on the development of nut-cracking skills in the chimpanzees of the taï forest, côte d'ivoire (pan troglodytes verus). | chimpanzees' (pan troglodytes) nut-cracking behavior represents one of the most complex forms of tool-use known among nonhuman animals. given the close phylogenetic relationship between these apes and humans, investigating how such complex behavior develops in immatures can reveal the evolutionary roots of the cognitive processes that enabled the evolution of outstanding technological skills in our lineage. in this study, we investigated whether maternal behavior directly enhanced nut-cracking s ... | 2019 | 31209909 |
| spontaneous attention and psycho-physiological responses to others' injury in chimpanzees. | previous studies have shown that humans experience negative emotions when seeing contextual cues of others' pain, such as injury (i.e., empathic pain), even without observing behavioral expressions of distress. however, this phenomenon has not been examined in nonhuman primates. we tested six chimpanzees (pan troglodytes) to experimentally examine their reactions to others' injury. first, we measured viewing responses using eye-tracking. chimpanzees spontaneously attended to injured conspecifics ... | 2019 | 31183591 |
| wild chimpanzees deprived a leopard of its kill: implications for the origin of hominin confrontational scavenging. | this study reports the first observed case of wild chimpanzees (pan troglodytes) obtaining animal prey freshly killed by a sympatric leopard (panthera pardus) and scavenging it with the leopard still nearby. this observation has important implications for the emergence of confrontational scavenging, which may have played a significant role in human evolution. many scholars agree that eating meat became important during human evolution, and hominins first obtained meat by scavenging. however, it ... | 2019 | 31182198 |
| cultural variation between neighbouring communities of chimpanzees at gombe, tanzania. | comparative animal studies have revealed the existence of inter-group differences in socially learned behaviours - so-called cultural variations. however, most research has drawn on geographically and thus environmentally separated populations, rendering it difficult to exclude genetic or ecological influences. to circumvent this problem, the behaviour of neighbouring groups from the same population can be juxtaposed - an approach which in wild chimpanzees (pan troglodytes) has revealed cultural ... | 2019 | 31164683 |
| crab-fishing by chimpanzees in the nimba mountains, guinea. | the significance of aquatic food resources for hominins is poorly understood, despite evidence of consumption as early as 1.95 million years ago (ma). here we present the first evidence of a non-human ape habitually catching and consuming aquatic crabs. chimpanzees (pan troglodytes verus) in the rainforest of the nimba mountains (guinea) consumed freshwater crabs year-round, irrespective of rainfall or ripe fruit availability. parties of females and offspring fished for crabs more than predicted ... | 2019 | 31151662 |
| cardiac structure and function characterized across age groups and between sexes in healthy wild-born captive chimpanzees (pan troglodytes) living in sanctuaries. | to comprehensively characterize cardiac structure and function, from infancy to adulthood, in male and female wild-born captive chimpanzees (pan troglodytes) living in sanctuaries. | 2019 | 31140849 |
| intra-community infanticide in wild, eastern chimpanzees: a 24-year review. | infanticide is well documented in chimpanzees and various hypotheses have been proposed to explain this behavior. however, since infanticide by chimpanzees is relatively rare, it has thus far not been possible to thoroughly test these hypotheses. here we present an analysis of the largest dataset of infanticides from a single community of chimpanzees, a full record of all intra-community infanticides and failed attempts at infanticide over a 24-year period for the sonso community of chimpanzees ... | 2020 | 31134473 |
| wild chimpanzees (pan troglodytes troglodytes) exploit tortoises (kinixys erosa) via percussive technology. | chimpanzees (pan troglodytes), one of humankinds' closest living relatives, are known to hunt and consume the meat of various animal taxa. although some researchers have presented indirect evidence that chimpanzees may also prey on tortoises, until now, direct observations of this behaviour did not exist. here, we provide systematic descriptions of the first observations of chimpanzee predation on tortoises (kinixys erosa). we made these unprecedented observations on newly habituated chimpanzees ... | 2019 | 31123270 |
| factors influencing wild chimpanzee (pan troglodytes verus) relative abundance in an agriculture-swamp matrix outside protected areas. | human population growth and anthropogenic activities are exacerbating pressures on biodiversity globally. land conversion is aggravating habitat fragmentation and non-human primates are increasingly compelled to live in forest-agricultural mosaics. in sierra leone, more than half of the wild chimpanzee population (pan troglodytes verus) occurs outside protected areas and competes for resources with farmers. our study area, in the moyamba district in south-western sierra leone, is practically dev ... | 2019 | 31095574 |
| possible mineral contributions to the diet and health of wild chimpanzees in three east african forests. | we present new data on the ingestion of minerals from termite mound soil by east african chimpanzees (pan troglodytes schweinfurthii) living in the budongo forest reserve, uganda, the gombe national park and the mahale mountains national park, tanzania. termite mound soil is here shown to be a rich source of minerals, containing high concentrations of iron and aluminum. termite mound soil is not, however, a source of sodium. the concentrations of iron and aluminum are the highest yet found in an ... | 2019 | 31090097 |
| preferential hand use by captive chimpanzees (pan troglodytes) in manual and tool digging. | digging for underground storage organs of plants has been reported in various populations of wild chimpanzees (pan troglodytes). however, it is unknown so far whether chimpanzees display lateral biases in manual digging as direct observations of this behavior are still lacking. it was therefore the aim of the present study to assess, for the first time, hand preferences for digging in a group of nine captive chimpanzees. we found that with only one exception, all individuals engaged in manual di ... | 2019 | 31006044 |
| infant carrying by a wild chimpanzee father at bulindi, uganda. | although infanticide by wild adult male chimpanzees has been reported from multiple sites, affiliative infant carrying by males is rare. we observed infant carrying by an alpha male chimpanzee at bulindi (uganda) on two consecutive mornings and collected faecal samples from the newborn infant female, her mother and all candidate fathers to determine whether the alpha male was the infant's father using a likelihood-based method of paternity assignment. in contrast to previous observations of male ... | 2019 | 31006043 |
| chimpanzees ( pan troglodytes) coordinate by communicating in a collaborative problem-solving task. | successful collaboration often relies on individuals' capacity to communicate with each other. despite extensive research on chimpanzee communication, there is little evidence that chimpanzees are capable, without extensive human training, of regulating collaborative activities via communication. this study investigated whether pairs of chimpanzees were capable of communicating to ensure coordination during collaborative problem-solving. the chimpanzee pairs needed two tools to extract fruits fr ... | 2019 | 30991932 |
| a comparison of methods to determine chimpanzee home-range size in a forest-farm mosaic at madina in cantanhez national park, guinea-bissau. | human activities impact the distribution of numerous species. anthropogenic habitats are often fragmented, and wildlife must navigate through human-influenced and 'natural' parts of the landscape to access resources. different methods to determine the home-range areas of nonhuman primates have not considered the additional complexities of ranging in anthropogenic areas. here, using 6 months of spatial data on the distribution of chimpanzee presence (feces, feeding traces, nests, opportunistic en ... | 2019 | 30982104 |
| bushmeat trade consequences predict higher anxiety, restraint, and dominance in chimpanzees. | more data are needed for a better understanding of the long-term influence of wider and combined stressful events in chimpanzee personality development. we evaluated the effects of bushmeat trade outcomes on the personality development in 84 african sanctuary chimpanzees. the chimpanzees presented different backgrounds regarding maternal care, social exposure, and abuse. we evaluated personality traits in chimpanzees using the cattell 16pf personality questionnaire, the first application of this ... | 2019 | 30957221 |
| laparoscopic repair of an umbilical hernia in a western chimpanzee (pan troglodytes verus) rescued in sierra leone. | laparoscopic umbilical hernia repair was performed in an adult female western chimpanzee (pan troglodytes verus) in a rescue centre in sierra leone. biological mesh and laparoscopic spiral tacks via three 5 mm laparoscopy ports were used to close a 4 cm hernia. the chimpanzee recovered quickly and the hernia did not recur. | 2019 | 30945314 |
| chimpanzee feeding ecology and fallback food use in the montane forest of nyungwe national park, rwanda. | almost all primates experience seasonal fluctuations in the availability of key food sources. however, the degree to which this fluctuation impacts foraging behavior varies considerably. eastern chimpanzees (pan troglodytes schweinfurthii) in nyungwe national park, rwanda, live in a montane forest environment characterized by lower primary productivity and resource diversity than low-elevation forests. little is known about chimpanzee feeding ecology in montane forests, and research to date pred ... | 2019 | 30941796 |
| root growth and dental eruption in modern human deciduous teeth with preliminary observations on great apes. | recent studies of dental development have indicated that root growth rates are linked to the eruption of some permanent tooth types in modern humans and pan troglodytes. little is known about the potential links between these aspects of dental development in deciduous teeth of any primate species. this histology study calculates the rate at which roots extend in length for human deciduous maxillary teeth and a small sample of deciduous canines and premolars from p. troglodytes and pongo pygmaeus ... | 2019 | 30904039 |
| simultaneous outbreaks of respiratory disease in wild chimpanzees caused by distinct viruses of human origin. | respiratory viruses of human origin infect wild apes across africa, sometimes lethally. here we report simultaneous outbreaks of two distinct human respiratory viruses, human metapneumovirus (mpv; pneumoviridae: metapneumovirus) and human respirovirus 3 (hrv3; paramyxoviridae; respirovirus, formerly known as parainfluenza virus 3), in two chimpanzee (pan troglodytes schweinfurthii) communities in the same forest in uganda in december 2016 and january 2017. the viruses were absent before the outb ... | 2019 | 30866768 |
| cortisol and oxytocin show independent activity during chimpanzee intergroup conflict. | the oxytocinergic system is involved in a range of functions, from attachment and social bonding to aggression and stress responses. whether oxytocin is released in response to a stressor, shows contradictory results across species and potential contexts-dependent differences. to avoid unintended contextual changes due to experimental procedures, we tested this question non-invasively in wild chimpanzees in an ecologically valid context. we collected endogenous hormonal measures during exposure ... | 2019 | 30851601 |
| risk factors for respiratory illness in a community of wild chimpanzees (pan troglodytes schweinfurthii). | respiratory illnesses have caused significant mortality in african great ape populations. while much effort has been given to identifying the responsible pathogens, little is known about the factors that influence disease transmission or individual susceptibility. in the kanyawara community of wild chimpanzees, respiratory illness has been the leading cause of mortality over 31 years, contributing to 27% of deaths. deaths were common in all age groups except juveniles. over 22 years of health ob ... | 2018 | 30839693 |
| informing protection efforts for critically endangered chimpanzees (pan troglodytes verus) and sympatric mammals amidst rapid growth of extractive industries in senegal. | updated information on critically endangered western chimpanzees (pan troglodytes verus) in senegal is urgently needed, given that gold mining is rapidly transforming landscapes and livelihoods. specifically, biodiversity assessments will better elucidate the chimpanzee extinction risk here and yield baselines for monitoring. we compared mammal species richness between fongoli (unprotected) and assirik in niokolo-koba national park to assess the efficacy of the only nationally protected area whe ... | 2019 | 30826809 |
| dust affects chewing efficiency and tooth wear in forest dwelling western chimpanzees (pan troglodytes verus). | in humans it has been shown that abrasive particles in the diet result in increased tooth wear and less intense chewing behavior, both of which decrease chewing efficiency. this behavioral response may also exist in non-human primates as a means to reduce the wear effect of dust-laden food. here we tested whether the periodical occurrence of abrasive dust particles in the diet of western chimpanzees affects tooth wear and reduces chewing efficiency. | 2019 | 30821351 |
| validating camera trap distance sampling for chimpanzees. | the extension of distance sampling methods to accommodate observations from camera traps has recently enhanced the potential to remotely monitor multiple species without the need of additional data collection (sign production and decay rates) or individual identification. however, the method requires that the proportion of time is quantifiable when animals can be detected by the cameras. this can be problematic, for instance, when animals spend time above the ground, which is the case for most p ... | 2019 | 30811079 |
| habitat differentiation among three nigeria-cameroon chimpanzee (pan troglodytes ellioti) populations. | ecological niche models (enms) are often used to predict species distribution patterns from datasets that describe abiotic and biotic factors at coarse spatial scales. ground-truthing enms provide important information about how these factors relate to species-specific requirements at a scale that is biologically relevant for the species. chimpanzees are territorial and have a predominantly frugivorous diet. the spatial and temporal variation in fruit availability for different chimpanzee popula ... | 2019 | 30805176 |
| bili-uéré: a chimpanzee behavioural realm in northern democratic republic of congo. | to improve our understanding of the evolutionary origins of culture and technology in humans, it is vital that we document the full extent of behavioural diversity in our great ape relatives. about half of the world's remaining chimpanzees (pan spp.) live in the democratic republic of congo (drc), yet until now we have known almost nothing about their behaviour. here we describe the insect-related tool technology of bili-uéré chimpanzees (pan troglodytes schweinfurthii) inhabiting an area of at ... | 2019 | 30799412 |
| adult sex ratio as an index for male strategy in primates. | the adult sex ratio (asr) is defined as the number of fertile males divided by the number of fertile females in a population. we build an ode model with minimal age structure, in which males compete for paternities using either a multiple-mating or searching-then-guarding strategy, to investigate the value of asr as an index for predicting which strategy males will adopt, with a focus in our investigation on the differences of strategy choice between chimpanzees (pan troglodytes) and human hunte ... | 2019 | 30771361 |
| survey of behavioral indices of welfare in research chimpanzees (pan troglodytes) in the united states. | chimpanzees demand specialized housing and care and the highest degree of attention to animal welfare. the current project used a survey method to collate information on chimpanzee housing and behavioral indices of welfare across all 6 of the chimpanzee research facilities in the united states. data were compiled on 701 chimpanzees ranging from 2 to 62 y old (mean age, 26.0 y). all chimpanzees except for one were socially housed; the median group size was 7 animals, and group sizes ranged from 1 ... | 2019 | 30764895 |
| gestural repertoire size is associated with social proximity measures in wild chimpanzees. | studying the communication systems of primates can provide insights into the evolutionary origins of human language. some theories propose that language evolved to help meet the demands of managing complex social relationships. examining the associations between sociality and communication in the great apes can help to identify the specific selection pressures that may have been important for language evolution. in particular, gestural communication is believed to be important because it is a re ... | 2019 | 30706956 |
| stable isotope variation in savanna chimpanzees (pan troglodytes verus) indicate avoidance of energetic challenges through dietary compensation at the limits of the range. | food scarcity is proposed to be a limitation to chimpanzees at the limits of their range; however, such a constraint has never been investigated in this context. we investigated patterns of δ13 c and δ15 n variation along a latitudinal gradient at the northwestern west african chimpanzee (pan troglodytes verus) range limit with the expectation that isotope ratios of chimpanzees at the range limit will indicate different dietary strategies or higher physiological constraints than chimpanzees furt ... | 2019 | 30693959 |
| a comprehensive analysis of chimpanzee (pan troglodytes)-specific line-1 retrotransposons. | long interspersed element-1 (line-1 or l1) is one of the most abundant retrotransposons in the primate genomes and has contributed to their genome diversity and variations during the primate evolution. among primate l1 subfamilies, l1pt subfamilies include pan troglodytes-specific l1s. l1pt elements have been successfully expanded in the chimpanzee genome since the divergence of human and chimpanzee lineages. however, only a few full-length l1pt copies were previously detected in the chimpanzee ... | 2019 | 30690181 |
| a roadmap for high-throughput sequencing studies of wild animal populations using noninvasive samples and hybridization capture. | large-scale genomic studies of wild animal populations are often limited by access to high-quality dna. although noninvasive samples, such as faeces, can be readily collected, dna from the sample producers is usually present in low quantities, fragmented, and contaminated by microorganism and dietary dnas. hybridization capture can help to overcome these impediments by increasing the proportion of subject dna prior to high-throughput sequencing. here we evaluate a key design variable for hybridi ... | 2019 | 30637963 |
| does group size matter? captive chimpanzee (pan troglodytes) behavior as a function of group size and composition. | the national institutes of health and the association of zoos and aquariums recommend that captive chimpanzees be housed in multi-male, multi-female, age-diverse groups of no less than seven individuals. these recommendations are rooted in the idea that captive chimpanzee groups should be modeled after free-ranging, wild, fission-fusion chimpanzee societies. however, captive chimpanzees do not face the environmental pressures faced by wild chimpanzees, including food scarcity, inter-group compet ... | 2019 | 30620093 |
| breaking through disciplinary barriers: human-wildlife interactions and multispecies ethnography. | one of the main challenges when integrating biological and social perspectives in primatology is overcoming interdisciplinary barriers. unfamiliarity with subject-specific theory and language, distinct disciplinary-bound approaches to research, and academic boundaries aimed at "preserving the integrity" of subject disciplines can hinder developments in interdisciplinary research. with growing interest in how humans and other primates share landscapes, and recognition of the importance of combini ... | 2018 | 30573938 |
| trabecular bone structure in the distal femur of humans, apes, and baboons. | trabecular bone structure has been used to investigate the relationship between skeletal form and locomotor behavior on the premise that trabecular bone remodels in response to loading during an animal's lifetime. the aim of this study is to characterize human distal femoral trabecular bone structure in comparison to three non-human primate taxa and relate the patterns of trabecular structural variation in the distal femur to knee posture during habitual locomotor behavior. a whole-epiphysis app ... | 2020 | 30548834 |
| chimpanzees ( pan troglodytes) are more averse to social than nonsocial risk. | social risk is a domain of risk in which the costs, benefits, and uncertainty of an action depend on the behavior of another individual. humans overvalue the costs of a socially risky decision when compared with that of purely economic risk. here, we played a trust game with 8 female captive chimpanzees ( pan troglodytes) to determine whether this bias exists in one of our closest living relatives. a correlation between an individual's social- and nonsocial-risk attitudes indicated stable indivi ... | 2019 | 30511893 |
| spontaneous social tool use in chimpanzees (pan troglodytes). | although there is good evidence that social animals show elaborate cognitive skills to deal with others, there are few reports of animals physically using social agents and their respective responses as means to an end-social tool use. in this case study, we investigated spontaneous and repeated social tool use behavior in chimpanzees (pan troglodytes). we presented a group of chimpanzees with an apparatus, in which pushing two buttons would release juice from a distantly located fountain. conse ... | 2018 | 30451529 |
| taste responsiveness of western chimpanzees (pan troglodytes verus) to five food-associated saccharides. | using a two-bottle choice test of short duration, we determined taste preference thresholds for sucrose, fructose, glucose, lactose, and maltose in three western chimpanzees (pan troglodytes verus). further, we assessed relative preferences for these five saccharides when presented at equimolar concentrations and determined taste preference difference thresholds for sucrose, that is, the smallest concentration difference at which the chimpanzees display a preference for one of the two options. w ... | 2019 | 30443802 |
| object permanence in giraffa camelopardalis: first steps in giraffes' physical cognition. | although behavior, biology, and ecology of giraffes have been widely studied, little is known about their cognition. giraffes' feeding ecology and their fission-fusion social dynamics are comparable with those of chimpanzees (pan troglodytes), suggesting that they might have complex cognitive abilities. to assess this, we tested 6 captive giraffes on their object permanence, short-term memory, and ability to use acoustic cues to locate food. first, we tested whether giraffes understand that obje ... | 2019 | 30372108 |
| like chimpanzees (pan troglodytes), pigeons (columba livia domestica) match and nash equilibrate where humans (homo sapiens) do not. | martin, bhui, bossaerts, matsuzawa, and camerer (2014) found that chimpanzee pairs competing in matching-pennies games achieved the nash equilibrium whereas human pairs did not. they hypothesized this outcome may be due to (a) chimpanzee ecology producing evolutionary changes that give them a cognitive advantage over humans in these games, and (b) humans being disadvantaged because the cognition necessary for optimal game play was traded off in evolution to support language. we provide data rele ... | 2019 | 30372107 |
| group and kin recognition via olfactory cues in chimpanzees (pan troglodytes). | primates were traditionally thought to have a reduced sense of smell. although there is now evidence that olfaction plays a greater role in primate social life than previously assumed, research on the sense of smell in non-human apes is scarce. chimpanzees sniff the ground and vegetation on boundary patrols, but the function of this behaviour is unclear. since chimpanzees are highly territorial and can kill individuals that do not belong to their own community, sniffing might function to gather ... | 2018 | 30355708 |
| parv4 found in wild chimpanzee faeces: an alternate route of transmission? | human parvovirus 4 (parv4, family parvoviridae, genus tetraparvovirus) displays puzzling features, such as uncertain clinical importance/significance, unclear routes of transmission, and discontinuous geographical distribution. the origin, or the general reservoir, of human parv4 infection is unknown. we aimed to detect and characterize parv4 virus in faecal samples collected from two wild chimpanzee populations and 19 species of captive non-human primates. we aimed to investigate these species ... | 2019 | 30343383 |
| persistence in gestural communication predicts sociality in wild chimpanzees. | a key challenge for primates is coordinating behaviour with conspecifics in large, complex social groups. gestures play a key role in this process and chimpanzees show considerable flexibility communicating through single gestures, sequences of gestures interspersed with periods of response waiting (persistence), and rapid sequences where gestures are made in quick succession, too rapid for the response waiting to have occurred. the previous studies examined behavioural reactions to single gestu ... | 2019 | 30338419 |
| a clinical study to evaluate the cardiopulmonary characteristics of two different anaesthetic protocols for immobilization of healthy chimpanzees (pan troglodytes). | to characterize the cardiopulmonary characteristics of two different anaesthetic protocols (tiletamine/zolazepam ± medetomidine) and their suitability for the immobilization of healthy chimpanzees undergoing cardiac assessment. | 2018 | 30314798 |
| heritability of gray matter structural covariation and tool use skills in chimpanzees (pan troglodytes): a source-based morphometry and quantitative genetic analysis. | nonhuman primates, and great apes in particular, possess a variety of cognitive abilities thought to underlie human brain and cognitive evolution, most notably, the manufacture and use of tools. in a relatively large sample (n = 226) of captive chimpanzees (pan troglodytes) for whom pedigrees are well known, the overarching aim of the current study was to investigate the source of heritable variation in brain structure underlying tool use skills. specifically, using source-based morphometry (sbm ... | 2019 | 30307488 |
| wild chimpanzees select tool material based on efficiency and knowledge. | some animals have basic culture, but to date there is not much evidence that cultural traits evolve as part of a cumulative process as seen in humans. this may be due to limits in animal physical cognition, such as an inability to compare the efficiency of a novel behavioural innovation with an already existing tradition. we investigated this possibility with a study on a natural tool innovation in wild chimpanzees: moss-sponging, which recently emerged in some individuals to extract mineral-ric ... | 2018 | 30305440 |
| social bonds facilitate cooperative resource sharing in wild chimpanzees. | why share when access to benefits is uncertain is crucial to our understanding of the evolution of humans' extensive cooperation. here, we investigated some of the different human sharing hypotheses and potential neuroendocrine mechanisms, in one of our closest living relatives, chimpanzees. the strongest predictor of sharing across food types was the presence of enduring and mutually preferred grooming partners, more than harassment, direct signalling, or trade. moreover, urinary oxytocin level ... | 2018 | 30305438 |
| countering infanticide: chimpanzee mothers are sensitive to the relative risks posed by males on differing rank trajectories. | infanticide by males is common in mammals. according to the sexual selection hypothesis, the risk is inversely related to infant age because the older the infant, the less infanticide can shorten lactational amenorrhea; risk is also predicted to increase when an infanticidal male's chance of siring the replacement infant is high. infanticide occurs in chimpanzees (pan troglodytes), a species in which male dominance rank predicts paternity skew. infanticidal male chimpanzees (if low-ranking) are ... | 2019 | 30302748 |
| personality links with lifespan in chimpanzees. | life history strategies for optimizing individual fitness fall on a spectrum between maximizing reproductive efforts and maintaining physical health over time. strategies across this spectrum are viable and different suites of personality traits evolved to support these strategies. using data from 538 captive chimpanzees (pan troglodytes) we tested whether any of the dimensions of chimpanzee personality - agreeableness, conscientiousness, dominance, extraversion, neuroticism, and openness - were ... | 2018 | 30296994 |
| rethinking the evolution of property and possession: a review and methodological proposition. | property is a key feature of modern human society; however, identifying the origin of this multifaceted behavior poses a formidable challenge. here, we explore the methodologies for researching the origin of property. we discuss how an interdisciplinary approach can shed light on how our human ancestors shifted behaviorally from possessing an object to having exclusive property control over it. possession occurs when social group members only respect an individual's claim to have exclusive acces ... | 2018 | 30290031 |
| functional validation of human-specific powerplex® 21 system (promega, usa) in chimpanzee (pan troglodytes). | this study was aimed to test the powerplex® 21 system (promega, usa), used for human identification applications for its positive cross-species applicability in chimpanzees (pan troglodytes) in order to identify heterologous strs which can be used for individual identification, paternity testing, relatedness establishment and reconstruction of pedigrees and studbook records for captive and wild chimpanzee breeding populations. | 2018 | 30285836 |
| the relationship between the abundance of the nigeria-cameroon chimpanzee (pan troglodytes ellioti) and its habitat: a conservation concern in mbam-djerem national park, cameroon. | understanding the relationship between great apes and their habitat is essential for the development of successful conservation strategies. the chimpanzee pan troglodytes ellioti is endemic to nigeria and cameroon, and occupies an ecologically diverse range of habitats from forests to forest-savannah mosaic in mbam-djerem national park (mdnp) in cameroon. the habitat variation in chimpanzees is poorly understood in mdnp which provides an excellent opportunity to assess ecological factors that sh ... | 2018 | 30285707 |
| scars on plants sourced for termite fishing tools by chimpanzees: towards an archaeology of the perishable. | chimpanzees are well-studied, but raw material acquisition for tool use is still poorly understood as sources are difficult to trace. this study pioneers the use of information that can be gleaned from plant scars made by chimpanzees while they source vegetation parts to manufacture termite fishing tools. source plant species, raw material types and locations relative to targeted termite mounds were recorded for populations at gombe, issa, and mahale in western tanzania. recovered bark, twig, an ... | 2018 | 30281817 |
| the body inversion effect in chimpanzees (pan troglodytes). | bodies are important social cues for animals. body recognition in humans is deteriorated by inversion. this inversion effect suggests the configural processing of bodies, which is different from the processing used for other objects. however, it is not known if this type of body processing exists in non-human primates. we tested seven chimpanzees using upright and inverted chimpanzee body stimuli and other stimuli in matching-to-sample tasks to examine the body inversion effect and the body part ... | 2018 | 30281635 |
| chiimp: an automated high-throughput microsatellite genotyping platform reveals greater allelic diversity in wild chimpanzees. | short tandem repeats (strs), also known as microsatellites, are commonly used to noninvasively genotype wild-living endangered species, including african apes. until recently, capillary electrophoresis has been the method of choice to determine the length of polymorphic str loci. however, this technique is labor intensive, difficult to compare across platforms, and notoriously imprecise. here we developed a miseq-based approach and tested its performance using previously genotyped fecal samples ... | 2018 | 30250675 |
| revisiting panda 100, the first archaeological chimpanzee nut-cracking site. | archaeological recovery of chimpanzee panda oleosa nut cracking tools at the panda 100 (p100) and noulo sites in the taï forest, côte d'ivoire, showed that this behavior is over 4000 years old, making it the oldest known evidence of non-human tool use. in 2002, the first report on the lithic material from p100 was directly compared to early hominin stone tools, highlighting their similarities and proposing the name 'pandan' for the chimpanzee material. here we present an expanded and comprehensi ... | 2018 | 30236627 |
| comparative investigations of social context-dependent dominance in captive chimpanzees (pan troglodytes) and wild tibetan macaques (macaca thibetana). | theoretical definitions of dominance, how dominance is structured and organized in nature, and how dominance is measured have varied as investigators seek to classify and organize social systems in gregarious species. given the variability in behavioral measures and statistical methods used to derive dominance rankings, we conducted a comparative analysis of dominance using existing statistical techniques to analyze dominance ranks, social context-dependent dominance structures, the reliability ... | 2018 | 30224738 |
| the presence of females induces elevated cortisol levels in an alpha male: experimental evidence in chimpanzees. | in group-living primates, it has been reported that the alpha male exhibits high concentrations of cortisol and testosterone in the context of mating competition. we investigated how the presence of females affected salivary cortisol and testosterone levels in males from a small captive group of chimpanzees (pan troglodytes). specifically, we assessed whether the presence of females resulted in a rapid increase in salivary cortisol and testosterone levels in the alpha male. | 2018 | 30222182 |
| measurement of sylvian fissure asymmetry and occipital bending in humans and pan troglodytes. | the evolution of human-specific lateralised functions such as language has been linked to the development of structural asymmetries in the brain. here we applied state of the art image analysis techniques to measure sylvian fissure (sf) asymmetry and occipital bending (ob) in 3d magnetic resonance (mr) images of the brain obtained in-vivo for 30 humans and 30 chimpanzees (pan troglodytes). sf morphology differed between species, with the human sf terminating more superiorly in right inferior par ... | 2019 | 30170149 |
| ontogeny and variability of trabecular bone in the chimpanzee humerus, femur and tibia. | trabecular bone structure is known to be influenced by joint loading during life. however, many additional variables have the potential to contribute to trabecular bone structure of an adult individual, including age, sex, body size, genetics, and overall activity level. there is little research into intraspecific variability in trabecular bone and ontogeny of trabecular bone structure, especially in nonhuman primates. | 2018 | 30159927 |
| the ontogeny of intentional communication in chimpanzees in the wild. | the onset of intentional communication in children's first year of life represents a major milestone in human cognitive development. similarly, it is well established that our closest living relatives, the great apes, communicate with signals characterized by at least first-order intentionality. despite the well-documented influence of developmental experiences on socio-cognitive abilities in apes, the developmental trajectory of intentional signal use as well as effects of social exposure remai ... | 2019 | 30156360 |
| tinea corporis by microsporum audouinii in a female chimpanzee (pan troglodytes) from guinea-bissau: a case report. | we report a microsporum audouinii infection in a female juvenile chimpanzee (pan troglodytes) presenting generalized dermatitis compatible with dermatophytosis. dermatophyte was identified by macro- and microscopic characterization of skin and scales cultures in mycosel agar. the topical treatment applied was effective, having the potential for dermatophytosis treatment in immunocompetent primates. | 2018 | 30142242 |
| sexual dimorphism of body size in an african fossil ape, nacholapithecus kerioi. | sexual size dimorphism in the african fossil ape proconsul nyanzae (18 million years ago, 18 ma) has been previously documented. however, additional evidence for sexual dimorphism in miocene hominoids can provide great insight into the history of extant hominoid mating systems. the present study focused on body mass (bm) sexual dimorphism in nacholapithecus kerioi from the middle miocene (16-15 ma) in africa. bootstrap analysis revealed that p. nyanzae bm sexual dimorphism was lower than that in ... | 2018 | 30119896 |
| visual attention, indicative gestures, and calls accompanying gestural communication are associated with sociality in wild chimpanzees (pan troglodytes schweinfurthii). | the challenges of life in complex social groups may select for complex communication to regulate interactions among conspecifics. whereas the association between social living and vocalizations has been explored in nonhuman primates, great apes also have a rich repertoire of gestures, and how the complexity of gestural communication relates to sociality is still unclear. we used social network analysis to examine the relationship between the duration of time pairs of chimpanzees spent in proximi ... | 2019 | 30113179 |
| nest-building behaviour by chimpanzees (pan troglodytes verus) in the non-protected area of diaguiri (kedougou, senegal): implications for conservation. | diaguiri is a non-protected area situated in south-eastern senegal. chimpanzees (pan troglodytes verus) have been living here since 1999 but information on the characteristics of their nest sites have been lacking until now. furthermore, we implemented nest survey methods recently standardised to arid landscapes during a national chimpanzee survey. variations in nest decay rates are poorly understood in savanna-woodland mosaic habitats. this study aims to describe in diaguiri: (1) the distributi ... | 2018 | 30089293 |
| an assessment of the efficacy of camera traps for studying demographic composition and variation in chimpanzees (pan troglodytes). | demographic factors can strongly influence patterns of behavioral variation in animal societies. traditionally, these factors are measured using longitudinal observation of habituated social groups, particularly in social animals like primates. alternatively, noninvasive biomonitoring methods such as camera trapping can allow researchers to assess species occupancy, estimate population abundance, and study rare behaviors. however, measures of fine-scale demographic variation, such as those relat ... | 2018 | 30088683 |
| touch-screen-guided task reveals a prosocial choice tendency by chimpanzees (pan troglodytes). | humans help others even without direct benefit for themselves. however, the nature of altruistic (i.e., only the other benefits) and prosocial (i.e., self and other both benefit) behaviors in our closest living relative, the chimpanzee, remains controversial. to address this further, we developed a touch-screen-guided task that allowed us to increase the number of trials for a thorough test of chimpanzees' prosocial and altruistic tendencies. mother-offspring dyads were tested in the same compar ... | 2018 | 30083456 |
| genetic analysis suggests dispersal among chimpanzees in a fragmented forest landscape in uganda. | habitat fragmentation is a leading threat to global biodiversity. dispersal plays a key role in gene flow and population viability, but the impact of fragmentation on dispersal patterns remains poorly understood. among chimpanzees, males typically remain in their natal communities while females often disperse. however, habitat loss and fragmentation may cause severe ecological disruptions, potentially resulting in decreased fitness benefits of male philopatry and limited female dispersal ability ... | 2018 | 30052284 |
| in silico mutational analysis and identification of stability centers in human interleukin-4. | interleukin-4 (il-4) is a multifunctional cytokine that plays a critical role in apoptosis, differentiation and proliferation. the intensity of il4 response depends upon binding to its receptor, il-4r. the therapeutic efficiency of interleukins can be increased by generating structural mutants having greater stability. in the present work, attempts were made to increase the stability of human il-4 using in-silico site directed mutagenesis. different orthologous sequences of il4 from pan troglody ... | 2018 | 30046620 |
| urinary oxytocin levels in relation to post-conflict affiliations in wild male chimpanzees (pan troglodytes verus). | many animals living in social groups have evolved behaviors to resolve conflicts between group members, behaviors thought crucial for maintaining stable group life. several hypotheses, based mainly on observational data, aim to explain how post-conflict (pc) affiliations, such as reconciliation and consolation, resolve conflicts by restoring relationships and/or alleviating anxiety. to examine a potential endocrinological mechanism of pc affiliations, we used an experimental-like procedure to in ... | 2018 | 30031684 |
| behavioral conservatism is linked to complexity of behavior in chimpanzees (pan troglodytes): implications for cognition and cumulative culture. | cumulative culture is rare, if not altogether absent in nonhuman species. at the foundation of cumulative learning is the ability to modify, relinquish, or build upon previous behaviors flexibly to make them more productive or efficient. within the primate literature, a failure to optimize solutions in this way is often proposed to derive from low-fidelity copying of witnessed behaviors, suboptimal social learning heuristics, or a lack of relevant sociocognitive adaptations. however, humans can ... | 2019 | 30024238 |
| emotion processing across and within species: a comparison between humans (homo sapiens) and chimpanzees (pan troglodytes). | for social species, recognizing and adequately yet quickly responding to the emotions of others is crucial for their survival. the current study investigates attentional biases toward emotions in two closely related species, humans and chimpanzees. prior research has demonstrated that humans typically show an attentional bias toward emotions. we here build on that literature by studying the underlying unconscious mechanisms within and across humans and chimpanzees and aim to gain insight into th ... | 2018 | 30024235 |
| shifting through the forest: home range, movement patterns, and diet of the eastern chimpanzee (pan troglodytes schweinfurthii) in nyungwe national park, rwanda. | populations of the endangered eastern chimpanzee (pan troglodytes schweinfurthii) are declining throughout their range. although nyungwe national park (nnp) harbors the largest remaining eastern chimpanzee population in rwanda, we know little about their space use and dietary patterns. we studied home range, movement, and diet of two communities of chimpanzees in nnp using daily tracking data (6:00 am to 6:00 pm) collected from 2000 to 2015. one community, mayebe, resided in the forest center, a ... | 2018 | 29992652 |
| chimpanzees overcome the tragedy of the commons with dominance. | competition over common-pool resources (cpr) is a ubiquitous challenge for social animals. many species face similar dilemmas, yet our understanding of the evolutionary trajectory of cpr social strategies remains unexplored. here, we provide a first look at the social strategies of our closest living relatives, chimpanzees (pan troglodytes), in two novel resource dilemma experiments. dyads of chimpanzees were presented with renewable resource systems, collapsible at a quantity-dependent threshol ... | 2018 | 29991747 |
| nocturnal activity in wild chimpanzees (pan troglodytes): evidence for flexible sleeping patterns and insights into human evolution. | we investigated occurrences and patterns of terrestrial nocturnal activity in wild chimpanzees (pan troglodytes) and modelled the influence of various ecological predictors on nocturnal activity. | 2018 | 29989158 |
| estimation of chimpanzee age based on dna methylation. | in wild animal conservation, knowing the age of an individual animal is extremely beneficial. however, estimating the age is difficult for many species. recently, epigenetics-based methods of estimating age have been reported. these studies were predominantly on humans with few reports on other animals, especially wild animals. in the present study, a chimpanzee (pan troglodytes) age prediction model was developed based on the elovl2, ccdc102b, and znf423 genes that may also have application in ... | 2018 | 29968770 |