Jo Fritz

Variables influencing the origins of diverse abnormal behaviors in a large sample of captive chimpanzees (Pan troglodytes)

The developmental origin of abnormal behaviors is generally associated with early rearing environments that lack sufficient physical and sensory stimulation. However, other factors should also be considered. A large sample of captive chimpanzees (128 males and 140 females) was surveyed for the presence or absence of 18 abnormal behaviors. Origin variables included the subjects source (zoo, pet, performer, or laboratory), rearing (mother‐ or hand‐reared), and sex. Animals were assessed while held at the Primate Foundation of Arizona, University of Texas M. D. Anderson Cancer Center, or White Sands Research Center. There was a confound among origin variables; more hand‐reared animals than expected were from laboratories. Logistic regression tested the relationship of rearing and source, with sex as a secondary predictor variable, to each of the abnormal behaviors. There was no clear association between any abnormal behavior and source. However, for coprophagy, relative to animals from the laboratory, zoo animals tended to show a higher prevalence, while performers tended to show a lower prevalence (when rearing and sex were controlled). Rocking and self‐sucking were significantly more likely in hand‐reared animals. Coprophagy and depilation of self were significantly more likely in mother‐reared animals. When rearing and source were statistically controlled, the only significant sex difference was a higher prevalence of coprophagy in females and a higher prevalence of rocking in males. In a second, smaller sample of 25 males and 33 females from Southwest Foundation for Biomedical Research, no significant sex association was found for coprophagy, urophagy, rocking, or self‐depilation. In this second sample, coprophagy was also significantly more likely in mother‐reared than hand‐reared subjects. The association of some abnormal behaviors with mother‐rearing suggests that some form of social learning may be involved in the origin of some of these behavior patterns. This indicates that some abnormal behaviors may not be always be indicative of reduced psychological well‐being in captive chimpanzees. Am. J. Primatol. 48:15–29, 1999.

A stereo music system as environmental enrichment for captive chimpanzees.

Music has been shown to have beneficial effects on humans but little is known about the effects of music on nonhuman primates in biomedical research settings. The authors monitored the effects of music on the behavior of captive chimpanzees and found that music had significant positive effects, including a reduction in agitated and aggressive behaviors.

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.

An Assessment of Early Differential Rearing Conditions- on later Behavioral Development in Captive Chimpanzees

Early rearing experiences have a major impact on later behavioral development in both the human and nonhuman primate. Observation of juvenile chimpanzees (N = 12) reared under four different paradigms were examined to note if a difference existed in affiliative, nonaffiliative, and stereotypical behaviors. The four rearing conditions were defined as either mother-reared by the chimpanzee mother or human handreared. The hand-reared were further divided by the following: rearing by a human caregiver in a manner that simulated chimpanzee mother-rearing, simulated chimpanzee mother-rearing but sent away to an alternate institution at age 2 through 3 years, and reared at an alternate institution with limited human interaction. No significant differences were noted in the rearing conditions with the exception of the subjects reared at an alternate institution. These subjects showed significantly more abnormal behaviors than the other three groups. The results may indicate a need for an early strong attachment figure in the chimpanzees life to alleviate stress and provide adequate behavioral development.

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.

Effects of Early Rearing History on Growth and Behavioral Development in Captive Chimpanzees (Pan troglodytes)

Chimpanzees have one of the longest developmental periods of any mammal (Pereira and Fairbanks, 1993). Development includes a lengthy period of physical maturation (Riopelle, 1963; Doran, 1997), cognitive development (Plooij, 1987; Tomasello et al., 1993, 1994), and behavioral changes as the animal advances from infant (0–3.9 years) to juvenile (4–6.9 years), adolescent (7–9.9 years), and adult (10+ years). Weaning from their mothers or from their nursery environment is a long, gradual process (Horvat et al., 1980; Horvat and Kraemer, 1981; Fritz et al., 1991; Howell et al., 1993). Juveniles and adolescents develop social skills and relationships with others and gain new behaviors including foraging, grooming, and sexual behavior (Riopelle, 1963; Mason, 1967; Russon, 1990; Tomasello et al., 1994). While the purpose of the long developmental period is debated, it likely functions to promote physical growth, the acquisition of survival skills, and development into a socially and sexually competent adult (Walters, 1987; Pereira and Fairbanks, 1993).

ORIGINAL ARTICLE: Heart disease is common in humans and chimpanzees, but is caused by different pathological processes: Heart disease in hominids

Heart disease is common in both humans and chimpanzees, manifesting typically as sudden cardiac arrest or progressive heart failure. Surprisingly, although chimpanzees are our closest evolutionary relatives, the major cause of heart disease is different in the two species. Histopathology data of affected chimpanzee hearts from two primate centers, and analysis of literature indicate that sudden death in chimpanzees (and in gorillas and orangutans) is commonly associated with diffuse interstitial myocardial fibrosis of unknown cause. In contrast, most human heart disease results from coronary artery atherosclerosis, which occludes myocardial blood supply, causing ischemic damage. The typical myocardial infarction of humans due to coronary artery thrombosis is rare in these apes, despite their human‐like coronary‐risk‐prone blood lipid profiles. Instead, chimpanzee ‘heart attacks’ are likely due to arrythmias triggered by myocardial fibrosis. Why do humans not often suffer from the fibrotic heart disease so common in our closest evolutionary cousins? Conversely, why do chimpanzees not have the kind of heart disease so common in humans? The answers could be of value to medical care, as well as to understanding human evolution. A preliminary attempt is made to explore possibilities at the histological level, with a focus on glycosylation changes.

ORIGINAL ARTICLE: Heart disease is common in humans and chimpanzees, but is caused by different pathological processes

Heart disease is common in both humans and chimpanzees, manifesting typically as sudden cardiac arrest or progressive heart failure. Surprisingly, although chimpanzees are our closest evolutionary relatives, the major cause of heart disease is different in the two species. Histopathology data of affected chimpanzee hearts from two primate centers, and analysis of literature indicate that sudden death in chimpanzees (and in gorillas and orangutans) is commonly associated with diffuse interstitial myocardial fibrosis of unknown cause. In contrast, most human heart disease results from coronary artery atherosclerosis, which occludes myocardial blood supply, causing ischemic damage. The typical myocardial infarction of humans due to coronary artery thrombosis is rare in these apes, despite their human‐like coronary‐risk‐prone blood lipid profiles. Instead, chimpanzee ‘heart attacks’ are likely due to arrythmias triggered by myocardial fibrosis. Why do humans not often suffer from the fibrotic heart disease so common in our closest evolutionary cousins? Conversely, why do chimpanzees not have the kind of heart disease so common in humans? The answers could be of value to medical care, as well as to understanding human evolution. A preliminary attempt is made to explore possibilities at the histological level, with a focus on glycosylation changes.

Vasectomy as a birth control modality for captive chimpanzees.

Since the 1997 moratorium on the breeding of captive chimpanzees, facilities have faced the challenge of preventing pregnancies while attempting to provide the animals with an enriched social environment. The authors describe the use of vasectomy as a birth control method in three adult chimpanzees.