Just how well do urban lizards sleep at night when compared to their rural cousins? To find out, a team of scientists from the Centre for Ecological Sciences (CES) at the Indian Institute of Science (IISc.), Bengaluru, spent many a night in people’s backyards, empty lots and underdeveloped sites looking for sleeping lizards.
“Poking around in neighbourhoods at night with headlights and fancy camera equipment often drew a lot of attention from people and the police, and the team had to explain what they were doing on several occasions,” said Nitya Mohanty, one of the researchers.
The team was hunting for a species of lizards, Rock Agamas, to study how urbanisation has affected their sleep patterns. They found that urban lizards ‘use sleep sites that mirror the structural, thermal and light properties of natural habitats’. What’s more, city lizards choose sleep sites that resemble that of their rural counterparts in the type of surface and the amount of light and heat received.
The findings were recently published in the peer reviewed journal Behavioural Ecology and Sociobiology . The authors noted that the remarkable flexibility in sleep behaviour displayed by urban lizards is likely to help them cope in a city.
Cities have changed the way we sleep and eat. And not just humans, but also birds, insects, mammals and reptiles.
Urban habitats can hamper an animal’s sleep quality and patterns due to higher temperatures, the presence of artificial structures like walls and buildings built by humans, and artificial light at night.
“What’s interesting is that both rural and urban lizards are dependent on rough, rocky substrates. While scientists have a reasonably good understanding of how animal brains work during sleep, how they sleep in the real world is not well known,” said Maria Thaker, associate professor at CES and senior author of the study. “We know from human literature that certain conditions allow us to sleep better than others, and some disrupt our sleep. But animals live in the real world with all these conditions … and we wanted to understand where and how they sleep in the wild,” she said.
To do this, researchers conducted night forays in rural and urban areas.. The temperatures of both urban and rural sleep sites were found to be similar. Urban sleep sites, however, were nine times more likely to be sheltered and covered as compared to rural sites, and this helped address the light problem in urban areas. This indicates that the lizards try to mitigate urban stressors by being flexible in their sleep site choices, and end up picking sites that resemble their rural sites.
Prof. Thaker highlighted the importance of studying how animals cope with anthropogenic environments: “The world is changing, and it is going to continue to change. So, if we know what it is that [other organisms] require to live here, then we can make some choices of our own to help keep them here.”
