The influence of pups on 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 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 toward monitors. We found that the presence and number of otter pups are 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 almost always displayed aggressive and defensive behaviors, regardless of whether otters were aggressive toward the lizards. These observations suggest that otters vary their aggression and vigilance levels depending on their group composition and the physical environment of their interactions with monitor lizards.

Agonism between family groups of cooperative breeding smooth-coated otters (Lutrogale perspicillata)

“…Agonistic interactions, while sporadic, are not rare. Although smooth-coated otters engage in several group behaviors, including group defense against predators (Bungum & Johns, 2022), defense of group territories against conspecifics may be what drives the delayed dispersal of older broods in this cooperatively breeding otter.…”

“…At the group level, the family structure may influence aggressiveness. The presence of pups could increase the aggression of a group (Bungum & Johns, 2022; Dyble et al, 2019), or it may lead to families being more defensive and less aggressive. However, our limited data did not support further discussion about these factors.…”

“…Video recordings were collected from otter watchers and citizen scientists in Singapore. Citizen science can be effective in animal behavior studies, and some studies glean data from public sources (Boydston et al, n.d.; Bungum et al, 2022; Bungum & Johns, 2022; Loong et al, n.d.). Gleaning data from public repositories can be particularly useful when the behavior is rare or difficult to find (Nelson & Fijn, 2013), like group territorial defense.…”