Daily activities of water monitors (Varanus salvator macromaculatus Deraniyagala, 1944) in urban wetland, Bangkok, Thailand

Abstract

From July to October 2015, a study was conducted on the water monitors (Varanus salvator macromaculatus) at Dusit Zoo in Bangkok, Thailand. A total of 90 monitors were captured, measured for SVL, sexed, and marked on the right axilla. The captured monitors included 70 females and 20 males, resulting in a sex ratio of 3.5:1. Body size did not differ significantly between genders. The monitors exhibited bimodal diurnal activity, with a focus on fish hunting in the morning (06:00–08:00 h) and scavenging for fish leftovers in the afternoon (15:00–17:00 h). After the monitor lizards hunted for prey in the morning, they spent 5–7 hours basking and floating in the lake during the afternoon. Sexual behaviors were also occasionally observed. The monitors displayed frequent predatory behavior towards natural prey, especially fish, in the morning, as opposed to opportunistically scavenging on tourist food and fish leftovers observed throughout the day.