Integrating Reference Intervals into Chimpanzee Welfare Research

SIMPLE SUMMARY: In recent years, animal welfare scientists have focused on developing novel approaches for improving the quality of life of chimpanzees living in zoos, sanctuaries, and laboratories. To evaluate the emotional, physical, and mental states of individual chimpanzees, welfare researchers are encouraged to integrate indicators that can be monitored non-invasively. In this study, we analyzed data from 40 adult chimpanzees from 16 zoological facilities to generate reference intervals (i.e., ranges of values) for behavioral and physiological measures of welfare. We also examined whether these measures varied by age or sex. While we discovered sex or age differences for a handful of behaviors, most behaviors and the physiological measures (fecal glucocorticoid metabolites, fecal immunoglobulin-A) did not vary by sex or age. Moving forward, animal care professionals can make informed decisions regarding management and husbandry practices by comparing an individual chimpanzee’s values to the reference intervals reported in this study. ABSTRACT: Animal welfare researchers are committed to developing novel approaches to enhance the quality of life of chimpanzees living in professional care. To systematically monitor physical, mental, and emotional states, welfare scientists highlight the importance of integrating non-invasive, animal-based welfare indicators. This study aimed to create species-specific reference intervals for behavioral measures and physiological biomarkers. Specifically, we analyzed data from 40 adult chimpanzees (22 females, 18 males) residing at 16 zoological facilities to generate reference intervals for behavioral states and events, behavioral diversity, fecal glucocorticoid metabolites (GCMs), and fecal immunoglobulin-A (IgA). Comparisons of sex and age using linear regression models revealed significant differences for several behaviors. The proportion of time spent engaged in mutual/multiple social grooming significantly decreased as individuals aged. Furthermore, males spent a higher proportion of time performing aggressive contact behaviors and displaying to other chimpanzees when compared to females. Males also performed sexual examination behaviors at a higher rate than females. Behavioral diversity, fecal GCM, and fecal IgA did not vary by sex or age. In the future, values for individual chimpanzees can be compared to the ranges reported here for particular age/sex classes. Ultimately, animal care professionals can utilize reference intervals to make evidence-based decisions regarding management practices and environmental conditions.