Climate change is taking a toll on crocodiles in Australia, according to a recent study. Estuarine crocodiles, also known as saltwater crocodiles, are facing challenges as global temperatures rise.
Crocodiles are cold-blooded creatures, meaning they rely on their environment to regulate their body temperature. When they need warmth, they bask in the sun. To cool down, they seek shade or plunge into cooler waters. But with the climate warming, these crocodiles are experiencing higher body temperatures, and this is changing how they behave.
Researchers studied crocodiles over a 15-year period and found that their average body temperature increased significantly. They discovered that these reptiles spent more days near their critical thermal limit of 89.6°F (32°C). Previous studies have shown that when temperatures reach this level, crocodiles struggle to swim and dive effectively. When overheated, they spend more time trying to cool off instead of being active.
Kaitlin Barham, the study’s lead author and a PhD candidate at the University of Queensland, explained, “When it’s hotter, crocodiles’ metabolisms increase. This means they use oxygen faster, making it harder for them to hold their breath.” They take longer to recover after swimming, which can affect their hunting and feeding habits.
The researchers monitored 203 crocodiles at the Steve Irwin Wildlife Reserve in Queensland between 2008 and 2023. They used acoustic devices implanted under the skin to track body temperatures and behaviors. If a crocodile was not detected for a while, and their temperature changed when they reappeared, scientists knew it was cooling off or warming up.
During this study, they collected almost 6.5 million temperature readings. They noted that body temperatures had risen nearly 1°F (0.55°C) over time, and many crocodiles reached or exceeded the critical temperature at least once. Notably, one crocodile maintained a temperature over the limit for more than a month back in 2021. The researchers linked high temperatures to periods of El Niño, which are becoming more frequent due to climate change.
Interestingly, the crocodiles showed more cooling behaviors on hotter days and spent less time submerged when temperatures soared. It’s still uncertain how these behavioral changes will impact their survival. While they are adapted to handle heat, extended periods of extreme weather could impede their ability to hunt effectively. As stealth predators, crocodiles rely on submerging themselves to surprise their prey along riverbanks.
Barham noted that every moment a crocodile is busy cooling down is a moment lost for hunting, mating, or traveling, which could affect their overall health in the long run.
