Stereotypic behavior and fecal cortisol level in captive giant pandas in relation to environmental enrichment

Stereotypic behavior is exhibited by a wide range of captive animals. Its association with hormones, especially elevated cortisol level and lack of naturalistic stimuli in the environment, has been little studied. This study hypothesizes that stereotypic behavior is caused by stress due to lack of appropriate, naturalistic stimuli in the environment. Using four adult pandas (Ailuropoda melanoleuca) in the Beijing Zoo from March–July in 2003, we tested the following predictions: 1) stereotypic behavior and fecal cortisol level will not change associated with the progress of reproductive state; 2) there is a positive correlation between the occurrence of stereotypic behavior and fecal cortisol level; and 3) environmental enrichment by adding a naturalistic stimulus will reduce both stereotypic behavior and fecal cortisol level. We did not find any significant differences in the occurrence of stereotypic behavior and fecal cortisol level but did find a significant difference in the total time engaged in displaying the stereotypic behavior among the three estrous periods. The level of stereotypic behavior was correlated with elevated fecal cortisol level. Enrichment simply by adding a naturalistic stimulus did not show significant effects on stereotypic behavior, or on fecal cortisol level. Our results supported the second prediction, but did not completely support the first and the third ones perhaps because of the small sample size. Additionally, our results showed that stereotypic behavior might be a response to a heightened level of cortisol.