Captive Chimpanzees\u27 (\u3ci\u3ePan troglodytes\u3c/i\u3e) Night-Time Enrichment Selection and Use

Captive chimpanzees (Pan troglodytes) engage with enrichment objects extensively during the daytime, yet relatively little is known regarding their use of available enrichment at night. This study examined night-time enrichment use in three adult chimpanzees at the Chimpanzee and Human Communication Institute. Every evening, the chimpanzees received a variety of enrichment objects. The objects belonged to one of nine categories. Night-vision video cameras recorded the chimpanzees’ night-time behaviors every Monday through Thursday from July 9 to August 9, 2012 (Carner et al., 2013). The present study used a focal animal, instantaneous sampling method (Martin & Bateson, 2007) to analyze the video files, and recorded all occurrences of contact with an enrichment object from 8 p.m. to 6 a.m. Other information recorded for each chimpanzee included the type of contact (active or passive) and the enrichment object category. The chimpanzees were in contact with enrichment 99.97% of the time (or 32,128 of 32,138 observations). They used blankets exclusively and did not show individual variability in the types of objects used. Contact type was primarily passive. The results of this study emphasize the importance of providing captive chimpanzees with object enrichment and nesting materials at night. These findings have implications for nest-building behavior and overall welfare in captive chimpanzees