Date Published: January 20, 2017
Publisher: Public Library of Science
Author(s): He Liu, Hejun Duan, Cheng Wang, Zhigang Jiang.
Stereotypies are commonly observed in zoo animals, and it is necessary to better understand whether ambient environmental factors contribute to stereotypy and how to affect animal welfare in zoo settings. This study investigated the relationships between stereotypic behaviors and environmental factors including ambient temperatures, humidity, light intensity, sound intensity and number of visitors. Seven giant pandas were observed in three indoor enclosures and three outdoor enclosures. Environmental factors were measured for both indoor and outdoor enclosures and the effect they had on stereotypical behaviors was investigated. Our research found that light intensity significantly correlated with all stereotypies behaviors. Higher environmental temperature reduced the duration of pacing but increased the frequency of pacing, the duration and frequency of door-directed, meanwhile the duration of head-toss. However, we found no noticeable effect of humidity on stereotypic behaviors except for the frequency of head-toss. We also found that sound intensity was not correlated with stereotypies. Finally, the growth of visitors was negatively associated with the duration of door-directed. These results demonstrated that various environmental factors can have significant effects on stereotypic behaviors causing the expression of various stereotypies. Thus, stereotypies in zoo animals may not simply represent suboptimal welfare, but rather might be adopted as a means of coping with an aversive environment.
Zoo environments, though they often strive to mimic natural environments, are necessarily different from an animal’s in-situ habitat. Stereotypic behavior is rarely observed in wild animals, which means that zoo-housed animals may reflect an abnormal interaction between animal and environment . Stereotypies are often associated with a variety of possible stressors, including inadequate control over environment and lack of opportunity to express natural behavior [2, 3]. Thus, stereotypies have often been used as behavioral measures of animal welfare or psychological well-being [4, 5, 6, 7]. Although the causes of stereotypic behavior are often unknown, stereotypies have been shown to be environmentally induced, developing in situations when an animal’s life is in some way less than optimal [1, 8, 9]. In such instances, it is thought that stereotypy is a homeostatic adaptation by zoo-housed animals to cope with their environment [10, 11, 12]. It is also suggested that stereotypic behavior may be one method by which captive animals pass their time, or use it as a substitute for normal free-ranging behavior [13, 14]. Furthermore, some authors have demonstrated that stereotypies have evolved as a kind of self-generated enrichment [4, 15].
In this study, environmental temperature ranged between -2.38°C and 29.20°C (Table 4). Ambient temperature negatively related with duration of pacing, but positively correlated with the duration of head-toss, the duration of door-directed, the frequency of door-directed and the frequency of pacing (P<0.05, Table 5). By contrast, ambient temperature did not significantly affect the other stereotypic behaviors such as the duration of head-weaving, the frequency of head-weaving and head-toss. Environmental humidity varied between 10.58% RH and 85.50% RH with a mean of 35.10% RH (Table 4). Pacing, door-directed, head-weaving and the duration of head-toss did not significantly correlate with RH. (P>0.05, Table 5).