Saltwater crocodiles in northern Australia are changing how they behave to cope with rising temperatures, spending more time cooling off and less time hunting as their bodies get dangerously hot, reported Cosmos Magazine.
What's happening?
Research published in Current Biology shows that since 2008, the highest body temperatures in these reptiles have increased by 0.55 degrees Celsius.
This matches local air temperature trends, which are rising 0.05-0.2 degrees per decade in northern Australia.
"As ectotherms crocodiles can't regulate their own temperature like birds and mammals," says Kaitlin Barham, a Ph.D. candidate at The University of Queensland and the study's lead author. "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.
"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."
Researchers tracked 203 crocodiles in Queensland's Cape York Peninsula using satellite trackers and internal temperature sensors. They found 65% of the animals exceeded their critical thermal limit of 32 degrees (90 degrees Fahrenheit) at least once, with 22% reaching dangerous temperatures above 34 degrees (93 Fahrenheit).
Why are overheating crocodiles concerning?
When crocs overheat, they can't perform normal behaviors needed for survival. Their hunting ability suffers dramatically.
"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," explains study co-author Professor Craig Franklin from the University of Queensland.
This heating forces them to surface more often to breathe and spend longer recovering, making them less effective hunters. They're also using more energy on cooling behaviors rather than finding food, staying safe, or reproducing.
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If these reptiles keep overheating, it could create broader problems for river ecosystems where they play a key role as top predators. Their struggle is a warning sign of how warmer temperatures affect wildlife.
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What can be done about overheating crocodiles?
The crocodiles are already helping themselves by adapting their routines. "We saw that crocs were putting a bit more effort into cooling behaviours," Barham explains. "That might be as simple as they're spending more time on the bank at night, rather than on the bank during the day."
Researchers suggest that if warming continues, these reptiles may need to move further south to cooler waters. The study team wants to examine how crocodiles in southern Queensland handle heat waves compared to their northern counterparts.
Scientists will continue monitoring these prehistoric survivors to better understand their adaptations.
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