Elaine N. Videan

Reproductive aging in captive and wild common chimpanzees: factors influencing the rate of follicular depletion

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). Am. J. Primatol. 71:271–282, 2009.

Development of guidelines for assessing obesity in captive chimpanzees (Pan troglodytes).

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 animals 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.

Reproductive Aging in Female Chimpanzees (Pan troglodytes)

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 females 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.

Attempting to reduce regurgitation and reingestion in a captive chimpanzee through increased feeding opportunities: a case study.

Persistent regurgitation and reingestion is an abnormal behavior seen in many captive NHPs, particularly gorillas and chimpanzees. Successful reduction of regurgitation in captive gorillas has been achieved by providing browse, such as branches and leaves, and feeding continuously throughout the day. However, this modality has not been tested in chimpanzees. The authors tested these methods in a 15-year-old male chimpanzee (Pan troglodytes) with a seven-year history of regurgitation and reingestion by alternately providing additional opportunities to forage or giving daily browse. The results show that providing browse on a daily basis models the feeding behavior of wild chimpanzees and is a successful way to reduce regurgitation and reingestion in a chimpanzee unresponsive to previous dietary changes.