Removing milk from captive gorilla diets: The impact on regurgitation and reingestion (R/R) and other behaviors

Abstract

To test whether milk consumption facilitates performance of regurgitation and reingestion (R/R) in captive gorillas, an experiment was conducted in which milk was removed from the gorilla diet at Zoo Atlanta. The study was conducted using a withdrawal design (BTB), in which a baseline period (B) of 10 days was followed by a treatment period (T) of 10 days, followed by a return to the baseline feeding protocol (B) for 10 days. The experiment was conducted in two phases: first, identifying whether the incidence of R/R was decreased by replacing milk with an equal volume of diluted fruit juice, and second, identifying whether the incidence of R/R was decreased by replacing milk with a smaller volume of undiluted fruit juice. Removal of milk from the diet led to a significant decrease in R/R in both phases and an increase in feeding behavior during the first phase. Seasonal differences in baseline behavior were also observed. The current study provides evidence that removal of milk from the captive gorilla diet may reduce undesirable behaviors such as R/R and may be a step toward better approximating the natural diet for captive gorillas. Zoo Biol 18:515–528, 1999. © 1999 Wiley-Liss, Inc.