Chocodiles may be at risk due to climate change. According to a new study, estuarine crocodiles (Crocodylus porosus) in Australia are facing troubles due to global warming.

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Crocodiles, like most reptiles, are ectothermic (cold-blooded). This means that their body temperature is regulated by the external environment rather than internal body processes, unlike in endothermic (warm-blooded) animals like mammals and birds.

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Crocodiles regulate their body temperature by lying in the sun to warm up or lying in the shade, cool streams, pools, or shores to cool down. However, the warming temperatures have increased their body temperatures, resulting in changes in their behaviour. 

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According to the research published in the journal Current Biology, the average body temperatures of crocodiles have risen by a small but significant amount over a period of 15 years. In addition, they spent more days at their critical thermal limit, which is 89.6 degrees Fahrenheit (32 degrees Celsius).

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Previous studies have indicated that crocodiles have reduced swimming and diving performance when their body temperatures are 89.6 F or higher, in an attempt to cool themselves by reducing activity.

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“A hotter croc has a higher metabolism,” the lead author of the paper Kaitlin Barham told Live Science. “Higher metabolism means burning oxygen more rapidly. Lab research found that they just couldn't hold their breath for as long. It would take them a bit longer to recover at the surface.”

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Barham is a doctoral candidate studying crocodile movement and behaviour at the University of Queensland, Australia. The researchers conducted research between 2008 and 2023 on 203 estuarine crocodiles (also called saltwater crocodiles) at the Steve Irwin Wildlife Reserve in Queensland. With the use of trackers, scientists monitored their body temperatures and time in water.

Change in behaviours

The researchers observed nearly 6.5 million temperature readings from the crocodile, with the highest body temperatures being increased by 0.99 F (0.55 C). While 135 of the crocodiles monitored had body temperatures over 89.6 F at least once, and one showed body temperatures above 89.6 F for more than a month in 2021. The highest body temperatures were linked to El Niño periods.

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It was also detected that their cooling behaviours were more frequent when temperatures were hotter. According to the tracking data, crocodiles also submerged themselves for a shorter time when temperatures were high. 

While it is unclear if the temperatures are affecting their survival, hotter weather may reduce their ability to hunt as they submerge themselves to ambush their prey on river shores.

“Every minute that they're up on the bank trying to bring their body temperature down is a minute that they're not spending travelling, reproducing or looking for food,” Barham said. “That could result in future indirect effects on their health.”

(With inputs from agencies)