The Water Monitor Lizard Varanus salvator: Behavior, Ecology, and Human Dimensions in Banten, Indonesia

Abstract

The water monitor lizard, Varanus salvator, is a large, ecologically flexible species commonly found in areas of human disturbance throughout its Southeast Asian range. The presence of anthropogenic resource subsidies may influence V. salvator behavior in such areas, potentially altering the social structure, ranging activity, and space use of this species. Overlapping human and V. salvator activity areas also create the potential for increased human-V. salvator conflict. We used behavioral observations and radio-telemetry to study V. salvator in an area of regular anthropogenic subsidy in Banten, Indonesia. We also conducted interviews with area residents to document local knowledge and to identify concerns regarding local herpetofauna. On Tinjil Island, Indonesia, we observed a higher incidence of intraspecific encounters among V. salvator in a human-subsidized area than in areas where animals foraged naturally. A greater number of agonistic interactions was also observed in the presence of food when compared to those in the absence of food. Our data suggest that on Tinjil Island a dominance hierarchy exists among V. salvator frequenting the area of anthropogenic subsidy. In addition, V. salvator activity areas appeared smaller in the dry season than in the wet season, when the island’s natural water and prey resources were more abundant. Similarly, V. salvator on the island showed increased use away from areas of anthropogenic subsidy in the wet season only. Through the interview process we learned that a local taboo prohibits the collection of V. salvator and Python reticulatus on Tinjil Island, but that the taboo is not observed in the nearby mainland villages, Muara Dua and Cisiih. In the villages, V. salvator is mainly considered a pest, but the meat of this species is also consumed for medicinal purposes. In our study V. salvator behavior in human-subsidized areas differed from that observed in wildland areas but varied temporally, indicating that anthropogenic subsidies may be more important for this population in the dry season when natural resources are less available. A location-specific taboo, official regulations, and anthropogenic subsidy serve to protect and maintain Tinjil Island’s V. salvator population. However, in nearby Muara Dua and Cisiih, local use for medicinal purposes and concerns over livestock depredation could lead to increased harvest and persecution of this species.