Mechanical implications of chimpanzee positional behavior.

Mechanical hypotheses concerning the function of chimpanzee anatomical specializations are examined in light of recent positional behavior data. Arm-hanging was the only common chimpanzee positional behavior that required full abduction of the humerus, and vertical climbing was the only distinctive chimpanzee positional behavior that required forceful retraction of the humerus and flexion of the elbow. Some elements of the chimpanzee anatomy, including an abductible humerus, a broad thorax, a cone-shaped torso, and a long, narrow scapula, are hypothesized to be a coadapted functional complex that reduces muscle action and structural fatigue during arm-hanging. Large muscles that retract the humerus (latissimus dorsi and probably sternocostal pectoralis major and posterior deltoid) and flex the elbow (biceps brachii, probably brachialis and brachioradialis) are argued to be adaptations to vertical climbing alone. A large ulnar excursion of the manus and long, curved metacarpals and phalanges are interpreted as adaptations to gripping vertical weight-bearing structures during vertical climbing and arm-hanging. A short torso, an iliac origin of the latissimus dorsi, and large muscles for arm-raising (caudal serratus, teres minor, cranial trapezius, and probably anterior deltoid and clavicular pectoralis major) are interpreted as adaptations to both climbing and unimanual suspension.     

Effects of spatial crowding on social behavior in a chimpanzee colony

Among mammals there is usually an increased frequency of aggressive interactions when population density increases. Conducted at the Arnhem Zoo, the present study examined the effects of spatial crowding on social behavior. Observations were carried out during three winter and two summer periods, using six distinct behavioral categories as dependent variables. The hypothesis that the behavior of individual chimpanzees would be intensified under crowded conditions was examined. Only absolute grooming changes supported the “density-intensity” hypothesis. Aggression data exhibited only a slight increase. Apparently, advanced mammalian forms, such as chimpanzees and human beings, are able to cope with crowding-induced stress by engaging in alternatives to overt aggression.     

Social behavior in a captive chimpanzee (Pan troglodytes) group

A group of captive chimpanzees, consisting of one adult male and three mother/infant pairs, was systematically observed over a 15-month period. Over 200 hr of data were collected, using both sequential and time sampling techniques, and compared to the available data on wild chimps. Unlike many captive groups, most behavior patterns were remarkably similar, both qualitatively and quantitatively, to that of wild chimpanzees including: play, grooming, infant sexual development, tool use, food sharing, prosocial partner preferences, and aggressive displays.     

The chimpanzee of Filabanga,western Tanzania

The chimpanzee (Pan troglodytes) of western Tanzania is found in one of the driest habitats of this species where openland vegetation, especially theBrachystegia, Julbernardia, andIsoberlinia woodlands, is dominant, while the evergreen or semi-evergreen rain forests (the riverine forests) are less developed, being confined to river basins. The chimpanzee seems to adapt to this dry country better than any of the other forest primates living there. The results of the study in Filabanga indicate that there are some methods of adaptation which enable the chimpanzee to survive in this harsh environment.

1. The chimpanzee uses openland vegetation to a comparatively large extent. TheBrachystegia bussei woodland especially, is utilized as a habitual nesting place and doubtless as an important feeding place.
2. In the Masito Hills, which comprises Filabanga, the localities where food is abundant change seasonally. The chimpanzees migrate over a wide range, estimated to be between 200 and 400 square kilometers, from an area where food has become scarce to an area where food is plentiful.
3. Areas where food is plentiful are shared by two or more unit groups of chimpanzee.
4. The grouping patterns of the chimpanzee enable it to utilize both the areas where food is scarce and those where it is abundant.

     

The genetic demography of a chimpanzee colony

Chimpanzees used for biomedical research must be bred in captivity because of restrictions on importation. Because they are large and expensive animals, population sizes at breeding facilities are limited. This implies that inbreeding at some level is inevitable and that genetic management techniques should be employed to minimize matings between related individuals. The purpose of this paper is to consider the genetic history of the chimpanzee colony at the Southwest Foundation for Biomedical Research (SFBR) and to suggest ways in which genetic variability may be affected by management schemes. A total of 339 chimpanzees resided at SFBR between January, 1980, and January, 1990. Although only one mating between related individuals has occurred so far, the average level of kinship in the colony and between potential breeders is increasing. Population structure techniques were employed to assess the mating patterns which have occurred and to explore the degree of change in the characteristics of potential mates. A “gene dropping” simulation method was used to predict expected levels of heterozygosity and strategies for maintaining variability by increasing the breeding portion of the population were evaluated using a simulation approach. © 1995 Wiley-Liss, Inc.     

Muscle architecture of the common chimpanzee (Pan troglodytes): perspectives for investigating chimpanzee behavior

Thorpe et al. (Am J Phys Anthropol 110:179–199, 1999) quantified chimpanzee (Pan troglodytes) muscle architecture and joint moment arms to determine whether they functionally compensated for structural differences between chimpanzees and humans. They observed enough distinction to conclude that musculoskeletal properties were not compensatory and suggested that chimpanzees and humans do not exhibit dynamically similar movements. These investigators based their assessment on unilateral limb musculatures from three male chimpanzees, of which they called one non-adult representative. Factors such as age, sex, and behavioral lateralization may be responsible for variation in chimpanzee muscle architecture, but this is presently unknown. While the full extent of variation in chimpanzee muscle architecture due to such factors cannot be evaluated with data presently available, the present study expands the chimpanzee dataset and provides a preliminary glimpse of the potential relevance of these factors. Thirty-seven forelimb and 36 hind limb muscles were assessed in two chimpanzee cadavers: one unilaterally (right limbs), and one bilaterally. Mass, fiber length, and physiological cross-sectional area (PCSA) are reported for individual muscles and muscle groups. The musculature of an adult female is more similar in architectural patterns to a young male chimpanzee than to humans, particularly when comparing muscle groups. Age- and sex-related intraspecific differences do not obscure chimpanzee-human interspecific differences. Side asymmetry in one chimpanzee, despite consistent forelimb directional asymmetry, also does not exceed the magnitude of chimpanzee-human differences. Left forelimb muscles, on average, usually had higher masses and longer fiber lengths than right, while right forelimb muscles, on average, usually had greater PCSAs than left. Most muscle groups from the left forelimb exhibited greater masses than right groups, but group asymmetry was significant only for the manual digital muscles. The hind limb exhibited less asymmetry than the forelimb in most comparisons. Examination of additional chimpanzees would clarify the full range of inter- and intra-individual variation.     

Advanced age influences chimpanzee behavior in small social groups

Management strategies for captive chimpanzees (Pan troglodytes) must begin to take into account the increasing age of the captive chimpanzee population. This study represents a baseline assessment of the relationship between advancing age and behavior among male and female chimpanzees living in pairs and trios in indoor/outdoor runs. Data collected on 14 old individuals (30–44 years old) and 20 younger adult individuals (11–22 years old) totaled 240 hours. Levels of agonistic and affiliative social behavior, non‐social activity, abnormal behaviors, and behavioral indicators of anxiety were evaluated. In the same captive setting, the behavior of old chimpanzees was significantly different from younger chimpanzees. Old chimpanzees showed less aggression and moved about their enclosures less. Old females behaved submissively more often than younger adult females; the reverse was found among males. However, affiliative social behavior occurred at similar levels in old and younger adult chimpanzees, implying continued need for social housing with advancing age. The effect of enrichment devices may differ for aged female chimpanzees, given their submissiveness and the lower levels of object manipulation found in aged subjects. These results suggest that aging in chimpanzees may be accompanied by altered patterns of social interaction, requiring careful attention to the compatibility of social partners. Zoo Biol 19:111–119, 2000. © 2000 Wiley‐Liss, Inc.     

Male chimpanzee behavior in relation to female ano-genital swelling

This study examined the relationships between male agonistic, affiliative, and sexual behaviors and female estrus condition in captive adolescent and young-adult chimpanzees (Pan troglodytes). Data on agonistic, affiliative, and sexual behaviors of 11 males living in three social groups were collected during daily 45 minute observations over a 5 month period. Female estrus condition was assessed daily using the relative size of the female's ano-genital swelling. It was hypothesized that the presence of maximally tumescent females would generate conflicts between males, so an increase in inter-male agonism was predicted. Males exhibited higher rates of agonism toward other males when at least one female in the group was maximally tumescent. Male affiliative behavior directed toward other males and social play with males were affected by the presence and number of maximally tumescent females. Male sexual behavior increased when maximally tumescent females were present.     

Generalization between productive use and receptive discrimination of names in an artificial visual language by a chimpanzee

In a computer-controlled artificial visual language by a chimpanzee, early development of the interaction between responses of two language modes,productive use and receptive discrimination, was investigated. In Experiment 1, receptive discrimination was established for the names of five colors and three objects which had been accurately used in the productive mode, and the result suggested that receptive learning develops independently of productive learning. After intramodal generalization of these names was shown by unreinforced probes in each mode in Experiment 2, intermodal generalization of 12 additional names, 6 in each direction,was examined in Experiment 3. A pair of color or object names was taught in one mode until its intramodal generalization was shown to be adequate and then transferred into the other mode. Two pairs concurrently examined in opposite directions were matched as a set. Successive evaluation of the three sets by unreinforced probes showed that the possibility of intermodal generalization gradually increased;the generalization was not found in either direction for the first set, but it proved significant in one direction for the second set and, consequently, in both directions for the third set. These results lead to the conclusion that the chimpanzee’s responses in the two language modes are mutually independent in early acquisition but facilitate one another at a later stage. The implications of these findings for the symbolic function of the naming skill are discussed. This article is based upon the dissertation submitted by the author to the Faculty of Science, Kyoto University, in partial fulfillment of the requirements for the Ph.D degree.     

Birthweight outcomes in Bolivia: The role of maternal height,ethnicity, and behavior

We identify maternal behavioral factors associated with birthweight in Bolivia using data from the Demographic and Health Survey (DHS) of 2003. We estimate birthweight as a function of maternal behavior and the child's sex and gestational age. We control for maternal height, ethnicity, education, and wealth, and for differences observed across Bolivian regions in educational and health outcomes, demographic indicators, and altitude. We find that maternal age, fertility record, and birth spacing behavior are the main observable behavioral factors associated with birthweight, and that maternal height is associated with gestational age, a main determinant of birthweight. We also find that after controlling for gestational age, both ethnicity and altitude have an insignificant effect on birthweight.     

An empirical evaluation of instantaneous and one-zero sampling of chimpanzee behavior

The behavior category in progress at theend of every 15 seconds of observation of chimpanzee behavior was recorded (instantaneous sampling) as was the occurrence or nonoccurrence of all defined categoriesduring every 15 second observation interval (one-zero sampling). The scores obtained using the above procedures were then correlated with the percent of net observation time, hourly rate, and mean bout duration of the behavior categories. One-zero sampling scores correlated very strongly with percent of net observation time and moderately with hourly rate and mean bout duration. Instantaneous sampling scores correlated very strongly with percent of net observation time and moderately with hourly rate and mean bout duration.     

Flexibility and persistence of chimpanzee (Pan troglodytes) foraging behavior in a captive environment

As a result of environmental variability, animals may be confronted with uncertainty surrounding the presence of, or accessibility to, food resources at a given location or time. While individuals can rely on personal experience to manage this variability, the behavior of members of an individual's social group can also provide information regarding the availability or location of a food resource. The purpose of the present study was to measure how captive chimpanzees individually and collectively adjust their foraging strategies at an artificial termite mound, as the availability of resources provided by the mound varied over a number of weeks. As predicted, fishing activity at the mound was related to resource availability. However, chimpanzees continued to fish at unbaited locations on the days and weeks after a location had last contained food. Consistent with previous studies, our findings show that chimpanzees do not completely abandon previously learned habits despite learning individually and/or socially that the habit is no longer effective.     

Reproductive success,postpartum maternal behavior,and masculine sexual behavior of neonatally androgenized female hamsters

Sex differences in maternal behavior induced by pup stimulation (sensitization) have been reported for rats and hamsters and may be affected by the presence or absence of perinatal androgen treatment. Postpartum maternal behavior and litter survival in golden hamsters treated with testosterone propionate (TP) as neonates were studied. A high dose of TP (300 μg) eliminated feminine reproductive capacity when given on Day 2 or 4 postpartum and had no discernible effect on Day 12. Treatment on Days 6, 8, or 10 resulted in treatment day-dependent deficiencies in reproductive success which fell short of sterility in most females. These deficiencies included low birth weight, weight gain, and higher litter losses than controls. However, the maternal behavior of TP dams, as measured by retrieval and crouching, appeared to be normal. The disparity between delivery and successful rearing of normal-weight young may include uterine incompetence, lactation deficiency, and hypercannibalism. Behavioral masculinization was a more sensitive index of neonatal androgen action than any aspect of defeminization, but the two phenomena were dissociated in individuals.