Light may influence morning basking behaviour in captive gharials

Like all crocodilians, Gangetic gharials regulate their body temperature using external heat sources. They warm their enormous bodies, which can grow to 15 to 20 feet in length, by basking on sandbanks, making it an important daily activity. Both temperature and light are important environmental cues for basking. However, a recent study on captive Gangetic gharials (Gavialis gangeticus) finds that light is a stronger cue than temperature for their morning basking movements. The researchers expected natural light to be a reliable indicator for gharials to determine the right time to bask on land, says Megha Khanduri, the study’s lead author and a postdoctoral researcher at the University of Helsinki, Finland. However, artificial lighting at night and the resulting light pollution can disrupt the relationship between natural light and temperature in the environment. The study finds that if light is the more dominant cue for basking, this disruption could lead gharials to bask at the wrong time, when air temperatures are not warm enough, or choose suboptimal basking sites. “Such behaviours could be potentially life-threatening as it can result in hypothermia,” says Khanduri. “If hatchlings leave the water earlier than the adults because of differences in sensitivity to light, it could also expose them to terrestrial predators in the early hours.” Radiant cue for basking The study was conducted on 382 captive gharials raised from eggs and housed in enclosures at the Deori EcoCentre in Madhya Pradesh. The eggs were collected from several nesting sites within the National Chambal Sanctuary between…This article was originally published on Mongabay