Why desert lizards are facing their own ‘cost-of-living’ crisis as global warming hikes their ‘energy bills’

MELBOURNE, Jan 22 — It’s a well-known fact that lizards like to bask in the sun to regulate their body temperature. But global warming is putting them under unprecedented pressure, which Australian researchers have likened to an increase in the “cost of living” for these cold-blooded reptiles.

In a study published in the journal Science, a research team from the University of Melbourne argues that global warming can “squeeze” the energy budget of lizards by increasing the amount of food they need to survive, while reducing the time they have to find it. In deserts, where heat is extreme and food scarce, these reptiles must therefore work harder to survive.

This phenomenon is comparable to an increase in the “cost of living,” but transposed to the animal world. “Cost-of-living is a concept humans are all too aware of, but the same concept applies to ectotherms — or cold-blooded animals — such as lizards. We just need to switch the currency from money to energy and realise that for lizards these costs and their ability to meet them depend on temperature,” the study’s lead author, Dr Kristoffer Wild, explains in a news release.

The research team observed that lizards that are active during the day, ie, diurnal lizards, are the most vulnerable to global warming. These reptiles need more energy to maintain their body temperature, a mechanism known as thermoregulation. As a result, they have less time to find food before the heat becomes overwhelming. Conversely, warmer nights favour their nocturnal counterparts, who can extend their hunting time. “In other words, it’s like diurnal lizards paying higher bills with fewer work hours, while nocturnal lizards can counter high bills by gaining extra work hours during the warmer nights,” says Dr Wild.

Reptiles under threat

The researchers modelled these energy balances using physical and biological data, which they then compared to field observations made over 50 years ago in the deserts of Australia and Africa. Their conclusions are unequivocal: regions that have already experienced significant temperature rises, such as Africa, will be the hardest hit. African desert lizards will have to expend more energy to survive, while having less time to feed, compared to their Australian counterparts.

In addition to increased energy requirements, other aggravating factors, such as reduced food resources and growing water needs, are putting further pressure on the desert habitats in which certain types of lizard live. A better understanding of these ecological processes is crucial to identifying the most threatened species and devising appropriate conservation strategies. “If we can better understand the ecological processes underpinning these cost-of-living pressures, we can better anticipate the species most at risk and act accordingly,” says Dr Wild.

Like many other animal species, lizards are facing a growing threat from climate change. An American study published in Science magazine in 2010 suggests that almost 40 per cent of the world’s lizard populations could be lost by 2080 if temperatures continue to rise and greenhouse gas emissions are not contained. Such a loss would not only disrupt the food chain, but also jeopardise the balance of ecosystems worldwide. — ETX Studio