Pilot Investigation: Testing Opaque Water as an Agonism Mitigating Visual Barrier for Nile Crocodiles (Crocodylus niloticus).

Abstract

This pilot investigation sought to evaluate the effectiveness of water opacity as an agonism-mitigation strategy in an all-male group of Nile crocodiles (Crocodylus niloticus). Crocodile behavior was monitored over 95 observation hours, split approximately equally between transparent water and opaque water conditions. In addition to agonism rates, the crocodiles' use of water was evaluated to ensure the change in their habitat did not disrupt utilization of the water, which is an important component of their thermoregulatory processes. Agonism rates were approximately equal between the transparent and opaque water conditions. The proportion of the group in water was lower in the opaque condition though the mean difference between conditions suggests that approximately two more crocodiles (out of a group size that ranged from 21 to 18 individuals) were in water in the transparent condition than opaque condition. Overall, these findings suggest the opaque water had little to no effect on the crocodiles' behavior as measured here. However, the opaque water may have increased environmental complexity. In nature, crocodiles navigate opaque water utilizing chemosensory and integumentary sensory modalities that are likely underutilized in transparent water commonly provided to crocodilians living in human care. Further research is needed to understand how opaque water may be enriching for crocodilians.