Investigating the relationship between abiotic factors and the behaviour of an All-Male Nile crocodile (Crocodylus niloticus) Group

Abstract

Abiotic factors can have notable effects on animal behaviour at both seasonal and daily time scales. Understanding these effects is a critical consideration in the management and welfare of animals in human care. Herein we evaluated social behaviour and space use patterns of an ex-situ all-male Nile crocodile (Crocodylus niloticus) group in relation to seasonal (month) and daily (temperature, humidity, precipitation, time of day) abiotic factors over two years. Our results suggest that abiotic factors have notable influences on Nile crocodile behaviour at both seasonal and daily time scales. Seasonal patterns of behaviour were distinct, particularly between winter-spring and summer. Agonism rates during winter-spring were twice that of those in summer. Wounding was low throughout the year; however, the odds of having a wound increased by at least a factor of six during the winter compared to all other seasons. Also, sociosexual behaviour was almost exclusively observed within three months during the winter-spring seasons. These changes suggest this ex-situ all-male group’s social structure was seasonally variable in a manner that appears similar to reproductive seasonal changes observed in in-situ crocodile populations. Additionally, the odds of a crocodile being in water were nearly five times greater in the summer than winter-spring, likely reflective of seasonal differences in thermoregulatory requirements. Daily atmospheric conditions had generally weaker influences on behaviour than season; however, notable changes were observed suggesting daily abiotic variation is an important consideration in crocodile management. For example, morning rates of agonism were 1.5 times greater than afternoon rates, and the odds of a crocodile being in water were 73 % greater in the morning than afternoon. Collectively, these findings emphasize that care and welfare decisions based on behavioural inference may be incomplete, or worse inaccurate, if abiotic influences are not considered.