SICB 2016: Stress on the Job – A Case Study of Anolis carolinenesis

Variables to measure stress in Anolis carolinensis

Does enrichment increase the well-being of Anolis carolinensis in captivity? Scientists become more and more aware of animal welfare, aiming to reduce stress levels of animals in captivity. Glenn Borgmans from the University of Antwerp (Belgium) was interested in the effect of environmental enrichment on stress levels of Anolis carolinensis. Glenn measured multiple variables to assess stress levels during an acclimation period (‘acclimation’) and subsequently under two experimental conditions: no enrichment (‘deprived’) and high amounts of enrichment (‘enrichment’). To asses stress levels, he measured body mass, tailbase width, heterophil/lymphocyte ratio (a measure of stress) in the blood, change in body coloration (brightness), fecal corticosterone levels and overall behavior.

Increased heterophil/lymphocyte ratio suggests that lizards are more stressed during acclimation period as compared to cages with no enrichment (deprived) or higher amounts of enrichment.

Animals during the ‘acclimation’ period showed significantly higher levels of stress than animals housed under ‘deprived’ or ‘enriched’ conditions. This is surprising, because acclimation cages provided a baseline level of enrichment that is most commonly used in research and pet trade. Interestingly, males and females showed differences in behavior when stressed. Males showed overall higher activity (walking and climbing) and females showed reduced levels of activity. No difference between males and females was found in other variables.

Glenn suggests that elevated stress levels during the acclimation period was due to stress experienced prior to the experiment. Individuals were obtained from pet trade and showed high levels of stress for most variables. In pet trade multiple anoles are housed together, which might increase stress levels and thus explain his findings. To test this hypothesis Glen would like to look at how density affects stress levels of lizards in captivity.