No abstract

In the wild, great apes sleep in beds they make by successively bending branches into an interwoven platform. These beds are functionally more closely related to human beds than they are to the nests and tree-holes used by other primate species. The idea that bed-building by great apes is learned behavior that is dependent on appropriate early experiences has been proposed but never fully tested. In the present study this hypothesis was indirectly tested in 73 captive adult chimpanzees (Pan troglodytes; 27 wild-born and 46 captive-born). Bed-building and use were tested experimentally by the introduction of three sets of bedding materials. Over 200 hr of scan-sampling data were collected during 45-min observations following introduction of the bedding material. The wild-born subjects built and used beds significantly more often than the captive-born subjects. Also, wild-born subjects used more complex techniques during construction. Captive-born subjects that were mother-reared through early adolescence spent more time building and using beds than their nursery-reared counterparts. These differences remained consistent even when previous adult experience with bedding (measured as naturalistic vs. traditional housing) was accounted for. These results suggest that bed-building is a learned behavior that requires early experience and practice for acquisition.

We examine and discuss evidence of contrasting differences in fertility patterns between captive and wild female chimpanzees, Pan troglodytes, as they age; in the wild females reproduce in their 40s, but captive studies suggest that menopause occurs around that time. Thus, despite the increased longevity generally observed in captive populations reproductive life span is shortened. We outline a hypothesis to explain the apparent differential pace of reproductive decline observed between wild and captive populations. The breeding schedules of captive primates may contribute to accelerated reproductive senescence because continuous cycling in captive animals results in early depletion of the ovarian stock and premature senescence. Available evidence supports the hypothesis that women with patterns of high oocyte loss experience earlier menopause. Chimpanzees in captivity live longer, and thus, similar to humans, they may experience follicular depletion that precedes death by many years. In captivity, chimpanzees typically have an early age at menarche and first birth, shorter interbirth intervals associated with short lactational periods as young mature faster, and nursery rearing, which allows mothers to begin cycling earlier. Variables typical of wild chimpanzee populations, including late age at menarche and first birth, long interbirth intervals associated with prolonged lactational periods, and a long period of female infertility after immigration, spare ovulations and may be responsible for the later age at reproductive termination. Finally, we describe and discuss the timing of specific reproductive landmarks that occur as female chimpanzees age, distinguishing between functional menopause (age at last birth) and operational menopause (end of cycling).

Many captive chimpanzees (Pan troglodytes) are subjectively considered to be overweight or obese. However, discussions of obesity in chimpanzees are rare in the literature, despite the acknowledged problem. No study to date has systematically examined obesity in captive chimpanzees. This project develops guidelines for defining obesity in captive chimpanzees through the examination of morphometric and physiologic characteristics in 37 adult female and 22 adult male chimpanzees. During each animal's biannual physical exam, morphometric data was collected including seven skinfolds (mm), body mass index (BMI), waist-to-hip ratio (WHR), and total body weight (kg). The morphometric characteristics were correlated with triglycerides and serum glucose concentration, to test the utility of morphometrics in predicting relative obesity in captive chimpanzees. Abdominal skinfold (triglyceride: F=3.83, P=0.05; glucose: F=3.83, P=0.05) and BMI (triglyceride: F=10.42, p=0.003; glucose: F=6.20, P=0.02) were predictive of increased triglycerides and serum glucose in females; however no morphometric characteristics were predictive of relative obesity in males. Results suggest that no males in this population are overweight or obese. For females, there were additional significant differences in morphometric (skinfolds, BMI, WHR, total body weight) and physiologic measurements (systolic and diastolic blood pressure, red blood cells) between individuals classified overweight and those classified non-overweight. Skinfold measurements, particularly abdominal, seem to be an accurate measure of obesity and thus potential cardiovascular risk in female chimpanzees, but not males. By establishing a baseline for estimated body fat composition in female captive chimpanzees, institutions can track individuals empirically determined to be obese, as well as obesity-related health problems. Zoo Biol 0:1-12, 2007. (c) 2007 Wiley-Liss, Inc.

No abstract

A host of ecological, anatomical, and physiological selective pressures are hypothesized to have played a role in the evolution of hominid bipedalism. A referential model, based on the chimpanzee (Pan troglodytes) and bonobo (Pan paniscus), was used to test through experimental manipulation four hypotheses on the evolution of hominid bipedalism. The introduction of food piles (Carry hypothesis) increased locomotor bipedality in both species. Neither the introduction of branches (Display hypothesis) nor the construction of visual barriers (Vigilance hypothesis) altered bipedality in either species. Introduction of raised foraging structures (Forage hypothesis) increased postural bipedality in chimpanzees. These experimental manipulations provided support for carrying of portable objects and foraging on elevated food-items as plausible mechanisms that shaped bipedalism in hominids.

A number of age-related changes in physiological functions have been identified in macaques and humans. However, few studies have examined physiological aging in chimpanzees, despite the increasing age of the chimpanzee population. We documented age-related changes in seven hematology and 17 clinical chemistry parameters in 49 adult chimpanzees (17 males, 32 females) as a comparative viewpoint with human and macaque aging. Longitudinal data were analyzed using weighted linear and quadratic mixed effects regression models. Male chimpanzees exhibited a significant age-related increase in anemia risk, based on significant decreases in hemoglobin (F(1,49)=12.45, P=0.0009) and hematocrit (F(1,49)=15.42, P=0.0003). Both sexes exhibited significant age-related decreases in both kidney and liver function. Decreases in kidney function were noted by significant increases in blood urea nitrogen (F(1,45)=3.92, P=0.036) and creatinine (F(1,50)=5.63, P=0.022) as well as changes in electrolyte (i.e., sodium, potassium, phosphorous, chloride) balance. Declining liver function was based on significant increases in globulin (F(1,46)=32.34, P<0.0001) and decreases in albumin (F(1,48)=23.42, P<0.0001). These changes were most evident beginning at 25-30 years of age in males and 30-35 years of age in females. We recommend amending chimpanzee age classes to categorize males over 25 years and females over 30 years as aged.

Published age-specific fertility rates document a sharp decline in female chimpanzee fertility after age 35 years. However, in contrast to data on human females, little else is known regarding reproductive aging in chimpanzees. We documented age-related changes in estrous cycling, hormone profiles, and reproductive physiology in 14 female chimpanzees (Pan troglodytes) ranging in age from 32 to 50 years. Estrous data were analyzed from daily cycle charts, averaging 14.1 years of cycle data per subject, after omission of gestational periods and postpartum amenorrhea. Concentrations of total luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol, and progesterone were assayed in serum samples taken biannually. Sample collection times were chosen to avoid the ovulatory LH and FSH peaks of the female's cycle and yielded a mean of 16.2 serum samples over an average of 14.0 years per subject. Analysis of cycle charts revealed a negative relationship between age and the length of the follicular phase (percentage of cycle days at maximal tumescence). There also were positive relationships between age and the length of the estrous cycle, the percentage of cycle days at complete detumescence (i.e. amenorrhea), and the frequency of irregular cycles. Analysis of hormonal data revealed curvilinear relationships between age and both LH and FSH, with peaks above the menopausal threshold occurring around ages 35-40 years. Cycle and hormonal changes were similar to those in perimenopausal and menopausal women, providing evidence of perimenopause (at 30-35 years) and menopause (at 40 years) in the chimpanzee.