Meade, T. M., Krall, C., Hutchinson, E. K. et al. 2013. An aquarium as a passive enrichment item and its effect on locomotor stereotypy in a group of singly housed rhesus macaques (Macaca mulatta). American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 619 (Abstract #PS58).

Locomotor stereotypies are behaviors often seen in singly housed rhesus macaques (Macaca mulatta) and are considered to represent a maladaptive response to captive environments. Social housing is the most effective means for decreasing abnormal behaviors but is sometimes unrealistic as a result of individual incompatibility or research needs. Active and passive enrichment items are therefore commonly used as a means to mitigate these behaviors. Active enrichment items allow physical manipulation and are frequently successful in reducing stereotypies. However, their beneficial effects are usually confined to relatively short periods of active use. Passive enrichment items are less well studied and the results are mixed. This study evaluated an aquarium with live fish as a passive enrichment item. We hypothesized that the frequency of locomotor stereotypy would decrease after its introduction to a group of singly housed rhesus macaques with a known history of stereotypy and self-injurious behavior. The study followed an ABBA design and each block was 2 wk in duration, consistent with the concurrent enrichment and cage wash rotation schedule. Behavior was scored at 15-s intervals for 2 h daily. The average frequency of locomotor stereotypy was calculated per individual for each time block. Statistical comparisons were made between blocks using ANOVA and post hoc tests. Unexpectedly, locomotor stereotypy significantly increased with introduction of the aquarium. Stereotypy frequency decreased over time and no significant difference was noted during the second 2 wk compared with baseline. However, once the aquarium was removed, frequency of stereotypy decreased to below baseline levels. We suspect that the increased rate of abnormal behavior is a manifestation of neophobia resulting from the stress of a novel environmental object. Therefore, in the context of reducing abnormal behavior, enrichment items may not always be beneficial and should be critically evaluated upon their introduction to a new group of animals.