Aggressive interactions between smooth-coated otters and water monitor
lizards in Singapore
Abstract
Smooth-coated otters (Lutrogale perspicillata) and Malayan water monitor
lizards (Varanus salvator) occupy similar habitats and and interact
regularly in Singapore’s waterways. These interactions have a range of
potential outcomes and are sometimes lethal. Few formal behavioral
studies exist for either species. We analyzed interactions between
otters and monitor lizards by gleaning data from publicly available
videos from citizen scientists to examine what factors influence
aggressive and defensive behaviors, and what influences vigilance in
otters. Behavioral sequence analysis revealed no obvious monitor lizard
behavior that predicted otter aggression towards monitors. We found that
the presence and number of otter pups is positively associated with
otter aggression. Otters also tended to be more vigilant in groups with
more pups, and more vigilant on land than water. Monitor lizards
displayed aggressive and defensive behaviors more frequently than did
otters, regardless of whether the otters were aggressive towards
lizards. These observations suggests that otters vary their aggression
and vigilance levels depending on the context of each interaction.