Behaviour 2019
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Why We Fight: Drivers of Agonism Between Smooth-Coated Otters and Malayan Water Monitors in Singapore
Haaken Bungum, Philip Johns. Yale-NUS College, Singapore, , Singapore

Smooth-coated otters (Lutrogale perspicillata) returned to Singapore recently; they live in large family groups (up to 20 individuals) in many of Singapore’s highly canalized waterways. Also common in these waterways are Malayan water monitor lizards (Varanus salvator). Both otters and monitors are opportunistic predators, and interact regularly. While interactions are often uneventful, monitors sometimes steal food from otters or attack young otter pups, and sometimes otters attack monitors; these attacks have resulted in the injury or death of monitor lizards. I studied otter-monitor interactions along the Pandan River in Singapore to determine what leads to aggressive encounters. I gathered videos from citizen scientists on online platforms and scored interactions between the two species. Using sequential analysis, I found the most consistent factor leading to otter aggression was the presence of otter pups. I further demonstrated that otters are more vigilant when more pups are present. This suggests that adult otters are responding to monitor lizards specifically as threats to their offspring, although monitor attacks on pups remain relatively rare.