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Johns Hopkins Bloomberg School of Public HealthCAAT

Animal Welfare Enhancement Awards - 2004 Recipients

Progress Report: The Effects of Light Intensity on Fecal Cortisol and Stereotypic Behavior in Adult Male Macaca mulatta
Amy M. Dupuy, BS, RALAT, M. Babette Fontenot, DVM, PhD, DACLAM
 University of Louisiana Lafayette


Currently, laws are vague regarding optimal lighting for primate well-being. While the Animal Welfare Act does address lighting requirements, the only exact specification for primates is that they be provided with regular diurnal lighting cycles and that lighting must be "sufficient for their well-being". In the Guide for the Care of Use of Laboratory Animals exact specifications for nocturnal animals are given however, no additional lighting specifications are given for other species because of the lack of scientific data on room light intensities for other animals. Therefore the purpose of this study was to determine the effects of light intensity on stereotypic and self-injurious behavior in adult male Macaca mulatta.


Seventeen adult male rhesus monkeys (aged 6-13) with a history of stereotypic and self-injurious behavior were divided into two groups, matched for age and stereotypic behavior. Each group was placed in two identical rooms and exposed to three lighting conditions: baseline (563 - 769 lux), low light (176 - 201 lux), and bright light (1391 - 1475 lux). The order of exposure for Group 1 was baseline (2 weeks), low light (4 weeks), baseline (2 weeks), and bright light (4 weeks), baseline (2 weeks). For Group 2, the order of exposure was reversed. Behavioral data was collected twice per week, balanced for time of day, throughout the study using a focal sampling technique. Behaviors were categorized into the following: self-injurious behavior (SIB), stereotypic, agonistic, and general.


It was found that animals initially housed in the bright light condition (Group 2) had significantly higher rates and durations of hair-plucking (p < 0.05), higher rates of self-biting (p < 0.05), environmental-directed stereotypy (p < 0.05), and scanning (p < 0.05) when subsequently housed in low light conditions. Animals initially housed the low light condition (Group 1), displayed higher rates of scanning when subsequently exposed to bright light conditions (p < 0.05). Overall, duration of scanning was higher in the low versus the bright light condition, regardless of the order of exposure (p < 0.05).


While no evidence of detrimental effects of any specific lighting condition on behavior were identified, these results suggest that animals exposed to bright light conditions may have more difficulty adapting to subsequent low light conditions. More research is required to examine potential mechanisms underlying adverse behavioral responses to low light found in the current study.