Warm Waters Put Heat-Loving Sharks at Risk

For millions of years, an evolutionary advantage helped great white sharks rule the oceans. This biological trait, however, may soon become their greatest weakness. A study published in the journal Science reveals that these iconic predators keep their bodies warmer than the surrounding seawater. As climate change causes ocean temperatures to rise, these sharks face the risk of fatal overheating. This research highlights a dangerous double threat facing these apex predators.

Several large shark and tuna species are known as 'mesothermic.' This scientific term describes animals whose bodies run hotter than their environment. These species require significantly more energy, or food, to maintain their elevated internal temperatures. They currently face a difficult situation. The oceans are warming, while their food supply is declining due to overfishing. As water temperatures rise, these species will likely be forced to migrate to cooler waters to survive.

Nick Payne, the lead author of the study, emphasized the constraints these animals face. Payne is an associate professor at Trinity College Dublin in Ireland. He noted, "If you’re a shark, you can’t just pop down to the supermarket and buy more food." Payne added that scientists are observing animals moving to adapt to climate change in every environment on land and in the sea. This phenomenon is simply another example of that global migration mechanism.

From the powerful great whites of South Africa to the slow-moving, filter-feeding basking sharks of Ireland, these mesotherms burn nearly four times as much energy as cold-blooded fish. Cold-blooded fish, which constitute most marine species, have body temperatures that match the water around them. When the ocean warms, mesothermic species have limited options. They must slow down, alter their blood flow, or dive deeper to find cooler water. They must perform these physical adjustments while simultaneously hunting for a food supply that is steadily shrinking.

Mesothermic fish are a rare group, making up less than 0.1 percent of all marine life. This exclusive group includes great white, thresher, and porbeagle sharks. These animals trap the heat generated by their metabolism to keep their bodies warmer than the seawater. This adaptation has been key to their evolutionary success. It allows for higher swimming speeds, improved hunting abilities, and long-distance migrations across vast oceanic distances.