Acoustic variation of pant hoot calls by male chimpanzees: a playback experiment

Pant hoots, a type of long-distance calls of chimpanzees (Pan troglodytes), were played back to two male chimpanzees in a group of seven captive individuals to determine if chimpanzees would modify those vocalizations in response to strange males. Subjects emitted pant hoots with higher rates of delivery, shorter duration of buildup, and lower minimum fundamental frequency of climax when they were presented with pant hoots of strangers than when they produced the calls spontaneously. Considering the direction of acoustical change, we concluded that the rate of delivery, duration of buildup, and minimum frequency of climax might be associated with the underlying emotional states of the callers rather than call matching. Individual difference between two subject males was significant in minimum frequency and duration of climax and in average frequency of call, which appears to reflect differences of the caller's age and social status. These results suggest that different acoustic variables relate to within- and interindividual differences of these vocalizations. Received: March 7, 2000 / Accepted: May 8, 2000     

The fate of defeated alpha male chimpanzees in relation to their social networks

Usurpation of alpha status by males is a relatively rare event among wild chimpanzees in the Mahale Mountains National Park, western Tanzania, where long-term field studies have been carried out since 1965. Here we report three such cases and compare the fate of those defeated alpha males. The formation of effective alliances with other adult males is considered to be crucial in determining what will happen to the defeated alpha male in the rank order after the loss of his status.     

New records of within-group infanticide and cannibalism in wild chimpanzees

Two cases of within-group infanticide and cannibalism were observed among the M Group chimpanzees of the Mahale Mountains, Tanzania. In both cases, victimized infants were male, 5 – 6 months of age, and in good health when killed. Four to five years have passed since the mothers of the victims immigrated into M Group as nulliparous immigrants. In one case the 2nd-ranking male was observed to detach the infant from the mother's belly. Both infants were finally killed by the alpha male after several adult males scrambled for the bodies. There was no evidence that the mothers had mated with males other than those of M Group. Nor was there evidence that the mothers had restrictive mating relationships with some of the M Group adult males. What little evidence is available shows that the mothers had mated mostly with adolescent and other immature males during their conception cycles. However, at least in one case, the mother began to mate more with adult males rather than with immature males after the infanticide. It is proposed that the function of within-group male infanticide can be explained by the male-male competition hypothesis developed for hanuman langurs and other nonhuman primates.     

The epidemiology of soil-transmitted helminth and protozoan infections in south-west Cameroon

A cross-sectional study of the prevalence, intensity and effects of soil-transmitted helminth and protozoan infections was undertaken among patients at the Buea Hospital Annex located in Buea sub-division of Cameroon. Stool samples from 356 subjects (174 males and 182 females) were collected and processed using standard concentration methods. Our results showed that 31.0% of subjects were infected with intestinal helminths and the prevalence was higher in females (32.4%) than in males (30.5%). A significantly higher prevalence was observed in rural (47.2%) than in urban areas (21.0%); significance < 0.1%. Prevalence was highest among those aged between 6 and 12 years (41.4%). The total prevalence of intestinal helminth infections were 19.3% for Ascaris lumbricoides, 14.0% for hookworm and 11.8% for Trichuris trichiura. The intensity of infection was unevenly distributed, with very heavy loads concentrated in a few individuals. Data also showed that 28.1% (100/356) of the subjects were infected with protozoans. Females showed a higher prevalence (28.6%; 52/182) than males (20.7%; 36/174). Also, there was a significantly higher prevalence in rural (34.0%; 49/144) than urban areas (18.4%; 39/212); significance < 0.1%. The age group 6-12 years again had a higher prevalence (37.1%; 26/70). The total prevalence of intestinal protozoans was: Entamoeba histolytica (24.4%), Entamoeba coli (11.2%) and Giardia lamblia (0.6%). These relatively heavy prevalences in patients may be reduced by appropriate medication and maintaining strict personal hygiene. Health education, clean water supply, good sewage management and a congenial environment will all help to minimize infection.     

Hormone responses to clomiphene citrate in young chimpanzees

The responses of gonadotropin and gonadal steroids to the administration of clomiphene citrate were studied in male and female chimpanzees, aged 3.6 to 9.9 years. Follicle-stimulating hormone (FSH) was significantly reduced after treatment in the prepubertal females (n = 4) and in early pubertal males (n = 2) but not in prepubertal males (n = 5). FSH was unchanged or increased in early pubertal females (n = 2) and late pubertal males (n = 2). There was no consistent response to treatment with clomiphene citrate by luteinizing hormone (LH) in either males or females, nor by 17 beta-estradiol in the females. Testosterone levels were reduced in the early pubertal males only. These results support the hypothesis that negative feedback by gonadal steroids is operative in prepubertal chimpanzees and that puberty is accompanied by a reduction in the sensitivity to such feedback.     

Comparative rates of violence in chimpanzees and humans

This paper tests the proposal that chimpanzees (Pan troglodytes) and humans have similar rates of death from intraspecific aggression, whereas chimpanzees have higher rates of non-lethal physical attack (Boehm 1999, Hierarchy in the forest: the evolution of egalitarian behavior. Harvard University Press). First, we assembled data on lethal aggression from long-term studies of nine communities of chimpanzees living in five populations. We calculated rates of death from intraspecific aggression both within and between communities. Variation among communities in mortality rates from aggression was high, and rates of death from intercommunity and intracommunity aggression were not correlated. Estimates for average rates of lethal violence for chimpanzees proved to be similar to average rates for subsistence societies of hunter–gatherers and farmers. Second, we compared rates of non-lethal physical aggression for two populations of chimpanzees and one population of recently settled hunter–gatherers. Chimpanzees had rates of aggression between two and three orders of magnitude higher than humans. These preliminary data support Boehms hypothesis.     

Visual and auditory conditional position discrimination in chimpanzees (Pan troglodytes)

Chimpanzee cognition has been studied predominantly through the visual modality, and much less through the auditory modality. The aim of this study was to explore possible differences in chimpanzees’ processing of visual and auditory stimuli. We developed a new conditional position discrimination (CPD) task requiring the association between a stimulus (from either the auditory or the visual modality), and a spatial position (left or right). The stimuli consisted of the face and voice of two individuals well known to the subjects (one chimpanzee and one human). Six chimpanzees participated in both the visual and the auditory conditions. We found contrasting results between the two conditions: the subjects acquired the CPD more easily in the visual than in the auditory condition. This supports previous findings on the difficulties encountered by chimpanzees in learning tasks involving auditory stimuli. Our experiments also revealed individual differences: the chimpanzee with the most extensive experience in symbolic visual matching tasks showed good performance in both conditions. In contrast, the chimpanzee expert in an auditory-visual intermodal matching task showed no sign of learning in either condition. Future work should focus on finding the most appropriate procedure for exploring chimpanzees’ auditory-visual cognitive skills.     

圈养黑猩猩血液生理生化指标测定

正动物园作为综合保护、科普宣传与公众教育的重要场所,在濒危物种的迁地保护工作中发挥着十分重要的作用(Kleiman et al.,2010)。然而,不同的濒危物种在生理学及生活史方面存在很大差异;加之部分物种的生物学信息匮乏,使得动物园的饲养繁育和疾病防控工作面临重大挑战。在常规体检及疾病诊断时,血液参数值有助于对动物机体的临床检查与诊断,解读动物的生理、营养和病理状态(胡翊群,2004;Etim et al.,2014),是及时发现动物     

A geometric morphometric analysis of heterochrony in the cranium of chimpanzees and bonobos

Despite several decades of research, there remains a lack of consensus on the extent to which bonobos are paedomorphic (juvenilized) chimpanzees in terms of cranial morphology. This study reexamines the issue by comparing the ontogeny of cranial shape in cross-sectional samples of bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) using both internal and external 3D landmarks digitized from CT scans. Geometric morphometric methods were used to quantify shape and size; dental-maturation criteria were used to estimate relative dental age. Heterochrony was evaluated using combined size-shape (allometry) and shape-age relationships for the entire cranium, the face, and the braincase. These analyses indicate that the bonobo skull is paedomorphic relative to the chimpanzee for the first principal component of size-related shape variation, most likely via a mechanism of postformation (paedomorphosis due to initial shape underdevelopment). However, the results also indicate that not all aspects of shape differences between the two species, particularly in the face, can be attributed to heterochronic transformation and that additional developmental differences must also have occurred during their evolution.     

Greeting behavior during party encounters in captive chimpanzees

Party encounter situations were experimentally produced in a group of captive chimpanzees (Pan troglodytes verus) at the Primate Research Institute of Kyoto University, Japan. During weekends all subjects (two adult males and five adult females) usually stayed together in the rooms (Baseline condition). Under experimental conditions, we shut passages between rooms to divide the subjects into two groups. We examined the effects of temporal separation of group members on affiliative interactions, aggressive interactions, and simple proximity. The frequency of affiliative interactions between male and female chimpanzees and between female chimpanzees increased when they encountered one another after separation, irrespective of male identity or housing history. Therefore we considered affiliative interactions between males and females during party encounters as being the response between separated individuals. The same tendency was not found in the frequency of affiliative interactions between females or between males. Unlike affiliative interactions, neither aggressive interactions nor simple proximity were influenced by separation.     

The clinical chemistry of chimpanzees: II. Gamma glutamyl transferase levels in hepatitis studies

Normal ranges for gamma glutamyl transferase (GGT) in chimpanzees were determined and categorized according to age and sex. Enzyme patterns presented for 36 cases of non-A, non-B (NANB) hepatitis and compared to others with hepatitis A and/or B show that the response of this enzyme to these viral agents in chimpanzees is comparable to that seen in human patients. The value of GGT determinations, in addition to aspartate aminotransferase and alanine aminotransferase for the differentiation of various types of viral hepatitis, is described.     

Reproductive function in aged female chimpanzees.

Reproductive function was evaluated in ten female chimpanzees (Pan troglodytes) aged 35-48 years. Forty-eight years is the longevity record for the chimpanzee. Data on cycle frequency and duration was available for seven animals. Most were cycling regularly until death, and all had experienced at least one menstrual cycle within one year of death. After exclusion of periods when the animals were pregnant or in postpartum amenorrhea, the mean cycle frequency (+/- standard error)/year was 9.54 +/- 0.20 in seven animals aged 15-25 (432 cycles analyzed) compared to 8.6 +/- 0.76 in the same animals at age 35 + years (405 cycles analyzed); this effect approached significance (p = 0.072, Mann-Whitney U-test). Cycle length of 16 cycles in each of seven animals aged 15-25 was 32.23 +/- 0.38 days. The same animals when aged over 35 had mean cycle lengths of 35.59 +/- 0.73. This difference was not significant, although cycle lengths clearly increased with age in some individual animals. In five aged animals for which mating data was available, appropriate exposure to a male occurred in 52 cycles, but only two pregnancies occurred; one pregnancy resulted in a live birth at age 38, the other in a stillbirth at age 40. This conception rate was 3.85% compared with 20% in the same animals aged 15-25. These data suggest greatly reduced fertility after age 35, although menstrual cycle frequency remained high. The persistence of menstrual cyclicity until death, which occurred due to natural causes at latest in the fifth decade, is in striking contrast to the human female in which menopause occurs in the fifth decade and death is often postponed for several more decades.     

Development of the sexual skin with pubertal maturation in female chimpanzees

We examined the adolescent development of the sexual skin of chimpanzees (Pan troglodytes) by daily observation, evaluation of swelling, and weekly photogrametry. Although the size of swelling differed with the individual, the development of sexual swelling followed four stages: (1) initial stage, the labial region began to show a slight swelling and recovery; (2) labial stage, swelling at the labial region became maximal; (3) anal stage, another swelling center appeared in the anal region and enlarged; and (4) full maturity stage, the labial and anal regions merged into a full swelling. Menarche occurred after the beginning of the anal stage, and the regular cycle was then established. All of the swelling stages and the peak swelling size are regarded as good indicators of reproductive maturation in chimpanzees.     

Familial incidence of multiple births in a colony of chimpanzees (Pan troglodytes)

This paper describes the incidence of multiple births in the Yerkes Chimpanzee colony for a period of about 63 years. Pedigrees are presented for all multiple births. They demonstrate the recurrence of twins in relatively few family lines which can be traced back to a small number of ancestors. The findings suggest that twinning is a family trait in chimpanzees and they support the hypothesis that the incidence of multiple births is genetically influenced in this colony. In addition, a relatively high level of inbreeding may have enhanced the incidence of multiple births in these family lines. Similar findings are known from human populations.     

An attempted within-group infanticide in wild chimpanzees

Two high-ranking adult male chimpanzees (Pan troglodytes) of M group in the Mahale Mountains National Park, Tanzania, tried to get a newborn female infant of an adult female who was born in M group. The mother was not seen to mate with these adult males during the probable conception cycle of the infant, but she disappeared from the group during the later cycle, when she may have been inseminated by a male of one of the neighboring unit groups. The adult males failed to get the infant because the grandmother of the newborn and her female friend cooperated to protect the mother and infant from attacks by the males. The sexual selection hypothesis for infanticide by adult male chimpanzees holds for this observed case. The sudden disappearance of another infant, a healthy female, strongly suggests the killing of female infants too. Therefore, the asserted male-biased infanticide in chimpanzees appears to be less tenable.     

The cognitive and cultural foundations of moral behavior

Does moral culture contribute to the evolution of cooperation? Here, we examine individuals' and communities' models of what it means to be good and bad and how they correspond to corollary behavior across a variety of socioecological contexts. Our sample includes over 600 people from eight different field sites that include foragers, horticulturalists, herders, and the fully market-reliant. We first examine the universals and particulars of explicit moral models. We then use these moral models to assess their role in the outcome of an economic experiment designed to detect systematic, dishonest rule-breaking favoritism. We show that individuals are slightly more inclined to play by the rules when their moral models include the task-relevant virtues of “honesty” and “dishonesty.” We also find that religious beliefs are better predictors of honest play than these virtues. The predictive power of these values' and beliefs' local prevalence, however, remains inconclusive. In summary, we find that religious beliefs and moral models may help promote honest behavior that may widen the breadth of human cooperation.     

Survey of gorillas (<Emphasis Type="Italic">Gorilla gorilla gorilla</Emphasis>) and chimpanzees (<Emphasis Type="Italic">Pan troglodytes troglodytes</Emphasis>) in Southwestern Cameroon

A study on the distribution and population density of the western lowland gorilla (Gorilla g. gorilla) and the central chimpanzee (Pan t. troglodytes) was undertaken between December 1997 and August 2000 in the Campo and Maan Forests in southwestern Cameroon. The aim of this survey was to estimate the densities of the apes in different parts of the area, to assess the importance of the region for the conservation of these endangered species and to determine the influence of human activities such as logging and hunting. The survey was based on night nest counts on a total of 665.5 km of line transects. The overall density in the Campo Forest was estimated at 0.2 gorillas/km² and at 0.63–0.78 chimpanzees/km². The overall density of chimpanzees in the Maan Forest was estimated at 0.8–1 individuals/km². Gorilla density in this area was too low to allow an estimation. The highest gorilla nest density was found in secondary forest. The gorilla density in unlogged forest was significantly lower. Chimpanzees showed a clear preference for less disturbed areas. In unlogged forest, old secondary forests (logging more than 23 years ago) and areas of recent logging with large remaining patches of primary forest, significantly higher densities were calculated than inside the more heavily exploited logging concession. In areas with both logging and high hunting pressure both species were rare or even absent. The Campo Maan area is considered a very important area for the conservation of gorillas and chimpanzees. Conservation measures are urgently required to reduce the impact of logging and hunting. The creation of the Campo Maan National Park in January 2000 is an important measure to preserve the unique biodiversity in this so far hardly protected area.     

A new cytotype of Simulium squamosum from south-west Cameroon

A new cytotype of Simulium squamosum Enderlein (Diptera: Simuliidae) (here named S. squamosum'D') is described from around Mount Cameroon in south-west Cameroon on the basis of sex-chromosome differences on the short arm of chromosome I. Two polymorphic inversions, IS-To (a new inversion) and IS-2, are partially Y linked. These inversions usually occur together, although IS-To has a higher frequency and is more strongly Y linked than IS-2. This sex-chromosome system has not been previously described and the occurrence and evolution of sex-chromosome systems in S. squamosum is discussed.