Differences in Behavior Between Elderly and Nonelderly Captive Chimpanzees and the Effects of the Social Environment

Abstract

The population of NIH-owned or NIH-supported captive research chimpanzees is quickly becoming aged, and the 1998 NIH breeding moratorium has resulted in a skewed age distribution. As such, behavioral management programs aimed at refining the care of an aging captive chimpanzee population have become increasingly important. However, little research exists that addresses the ways in which captive chimpanzee behavior differs as a function of the interaction of age and aspects of the captive environment. We examined overall differences in behavior between elderly (35 y and older) and nonelderly (younger than 35 y) captive chimpanzees. Elderly chimpanzees exhibited significantly more rough scratching (a behavioral indicator of anxiety) and inactivity, less behavioral diversity, and less affiliation than their nonelderly counterparts. We also assessed whether elderly chimpanzee behavior and wounding rates differed as a function of housing in geriatric (group average age, 35 y or older) or nongeriatric (group average age, younger than 35 y) groups. In our program, geriatric social groups were characterized by smaller group size, more females within the group, and higher levels of individual mobility impairment compared with nongeriatric groups. Furthermore, elderly chimpanzees housed in geriatric groups displayed significantly increased rough scratching, decreased locomotion and submission than nongeriatric animals but no difference in wounding. These findings suggest that housing elderly chimpanzees in nongeriatric groups may be beneficial, given that doing so may stimulate locomotion. However, the establishment and maintenance of geriatric groups may be unavoidable as the demographics of the population of captive former research chimpanzees continues to age. Therefore, refinements to captive geriatric care strategies for chimpanzees should focus on methods of evaluating and enhancing functionally appropriate captive environments within geriatric groups.

Validation and utility of a body condition scoring system for chimpanzees (Pan troglodytes)

“…Behavioral observations were collected between July 2016 and May 2018 (Neal Webb et al, 2019; Neal Webb, Hau, & Schapiro, 2018) for 120 of the 158 chimpanzees described above. Observations consisted of 15‐min, continuous focal‐animal sampling.…”

“…It is important to note that obesity is not the only weight issue that can present in chimpanzees (although it is certainly the more common one). Geriatric (35 years and older; Neal Webb, Hau, Lambeth, & Schapiro, 2019) and ill chimpanzees may experience weight loss due to chronic conditions, infection, severe stress, or simply as a function of aging (Davenport, Menzel, & Rogers, 1966; Goodall, 1986; Terio et al, 2011; Williams et al, 2008). This can be difficult to identify over extended periods, as caregivers and veterinarians likely see the individual often, making subtle changes difficult to distinguish.…”

The implementation and initial evaluation of a physical therapy program for captive chimpanzees (Pan troglodytes)

“…These chimpanzees frequently face physical conditions related to old age, including arthritis, mobility impairments, stroke, and resulting paresis, as well as injuries that require extended healing times (Kawanaka, 1993; Lacreuse, Russell, Hopkins, & Herndon, 2014; Lowenstine et al, 2016; Nunamaker et al, 2012). Captive chimpanzees also experience multiple behavioral changes during old age, including lower levels of affiliative and social behavior, less diversity in behavior, and higher levels of inactivity and anxiety‐related behavior (Baker, 2000; Lacreuse et al, 2014; Neal Webb, Hau, Lambeth, & Schapiro, 2019; Riopelle & Rogers, 1965; Tarou, Bloomsmith, Hoff, Erwin, & Maple, 2002).…”

“…Personalized care routines that include acupuncture, laser therapy, and medication choice paradigms have resulted in chimpanzees voluntarily participating in their own health care, resulting in increased mobility and choice within the captive environment (Haller, Magden, Lambeth, & Schapiro, 2012; Lambeth, Schapiro, Bernacky, & Wilkerson, 2013; Magden, 2017; Magden et al, 2013; Neal Webb et al, 2018b). Evaluations of aspects of the physical and social environments of geriatric animals have led to structural enhancements to the physical environment and increased knowledge of the ways that social group composition affects geriatric chimpanzee behavior (Bridges et al, 2015; Bridges, Powers, Lambeth, & Schapiro, 2016; Neal Webb et al, 2019). More precise definitions of normal physiological parameters for aged individuals, including cholesterol, glucose, and lymphocyte counts, have led to the enhanced veterinary understanding of typical aging in chimpanzees (Ely, Zavaskis, & Lammey, 2013; Lowenstine et al, 2016; Nehete et al, 2017).…”

“…. Captive chimpanzees also experience multiple behavioral changes during old age, including lower levels of affiliative and social behavior, less diversity in behavior, and higher levels of inactivity and anxiety-related behavior (Baker, 2000;Lacreuse et al, 2014;Neal Webb, Hau, Lambeth, & Schapiro, 2019;Riopelle & Rogers, 1965;Tarou, Bloomsmith, Hoff, Erwin, & Maple, 2002).…”