linguistic:translation, structural:summarization
Captivity

Gorillas became highly prized by western zoos since the 19th century, though the earliest attempts to keep them in captive facilities ended in their early death. In the late 1920s, the care of captive gorillas significantly improved. Colo (December 22, 1956 – January 17, 2017) of the Columbus Zoo and Aquarium was the first gorilla to be born in captivity.

Captive gorillas exhibit stereotypic behaviors, including eating disorders — such as regurgitation, reingestion and coprophagy — self-injurious or conspecific aggression, pacing, rocking, sucking of fingers or lip smacking, and overgrooming. Negative vigilance of visitor behaviors have been identified as starting, posturing and charging at visitors. Groups of bachelor gorillas containing young silverbacks have significantly higher levels of aggression and wounding rates than mixed age and sex groups.

The use of both internal and external privacy screens on exhibit windows has been shown to alleviate stresses from visual effects of high crowd densities, leading to decreased stereotypic behaviors in the gorillas. Playing naturalistic auditory stimuli as opposed to classical music, rock music, or no auditory enrichment (which allows for crowd noise, machinery, etc. to be heard) has been noted to reduce stress behavior as well. Enrichment modifications to feed and foraging, where clover-hay is added to an exhibit floor, decrease stereotypic activities while simultaneously increasing positive food-related behaviors.

Recent research on captive gorilla welfare emphasizes a need to shift to individual assessments instead of a one-size-fits-all group approach to understanding how welfare increases or decreases based on a variety of factors. Individual characteristics such as age, sex, personality and individual histories are essential in understanding that stressors will affect each individual gorilla and their welfare differently.