Crocodiles are losing their cool over climate change, and researchers say it's having detrimental effects on the behaviour of the hardy tropical predators.
Research led by the University of Queensland's School of the Environment has found that crocodiles in northern Australia are heating up as the climate warms, and higher body temperatures mean they're forced to spend more time trying to stay cool.
The researchers analysed 15 years of information from sensors and trackers on 203 wild saltwater crocodiles on the Wenlock and Ducie rivers on Cape York Peninsula.
PhD candidate Kaitlin Barham, who co-authored the research published in Current Biology, said crocodiles were spending more time at or close to their critical thermal limit of 32-33C.
"(Because they're cold-blooded), crocodiles can't regulate their own temperature like birds and mammals, so as their environment is becoming warmer, the animals in our study are also getting hotter and needing to spend more time on cooling behaviours," Ms Barham said.
"But if their time and energy is dominated by the need to stay cool, activity necessary for hunting, keeping safe from predators or reproducing is reduced."
Cooling behaviours include basking on riverbanks nocturnally, sitting in the shade for evaporative cooling, and finding cooler, deep pockets of water.
Increases in both air and water temperatures were impacting the crocodiles and co-author Craig Franklin said their diving and swimming performance was affected.
"Hotter crocodiles don't dive for as long which is concerning, because as ambush hunters, they need to wait underwater holding their breath for a wallaby or feral pig to come past," Professor Franklin said.
The research results were "definitely something to keep an eye on", but the crocodiles were still coping, Ms Barham said.
The researchers' next step is to examine the impacts behaviour change is having on the overall health of the crocodile population.
Since 2008, the temperature peaks experienced by the crocodiles in the study have increased by 0.5C and their median body temperature has increased by 0.11C.
The long-term research project is a collaboration with crocodile experts from Australia Zoo and is based at the Steve Irwin Wildlife Reserve.
