Great White Sharks Face Overheating in Warming Oceans

For millions of years, the ability to maintain a warm body temperature gave great white sharks a significant advantage. This trait helped them dominate as top ocean predators. However, this same evolutionary edge is now becoming a serious liability. As the oceans warm due to climate change, these sharks face the risk of potentially fatal overheating. This conclusion comes from a new scientific report published in the journal Science.

A group of large tuna and shark species are known as "mesotherms." This term describes animals that can keep their body temperatures warmer than the surrounding seawater. Maintaining this warmth requires a lot of energy, which comes from food. Now, these species face a double threat. The oceans are warming, and their food supply is declining, often due to overfishing. As water temperatures rise, these animals will be forced to move to cooler areas to survive.

Nick Payne, the lead author of the study, is an associate professor at Trinity College Dublin in Ireland. He explained the urgency of the situation: "If you’re a shark, you can’t just pop down to the supermarket and buy more food." He noted that we are seeing animals move with climate change in every environment on land and in the sea. This study is simply another example of that mechanism.

Mesothermic fish are a rare group. They make up less than 0.1 percent of all marine life. This group includes great white sharks, thresher sharks, porbeagle sharks, and basking sharks. It also includes large tuna like the Atlantic bluefin. These animals trap heat generated by their own metabolism. This allows them to stay warmer than the water around them. This internal warmth has been a key evolutionary advantage. It enables higher swimming speeds, better hunting skills, and long-distance migrations.

However, this advantage comes with a high cost. These mesotherms burn nearly four times as much energy as cold-blooded fish. Cold-blooded fish, like most other sharks and fish, have body temperatures that match the surrounding water. As the oceans warm, mesotherms must find ways to cool down. They might slow their activity, change their blood flow, or dive to deeper, cooler water. They must do all this while hunting for a food supply that is shrinking.