Great white sharks are overheating

The evolutionary traits that have allowed great white sharks to thrive for millions of years are now turning into a potential hazard. These apex predators maintain a body temperature that is warmer than the surrounding ocean, a feature that is becoming increasingly perilous as global temperatures rise. A recent study published in Science reveals that great whites and other 'mesothermic' species now face the looming threat of overheating due to climate change. As ocean waters warm, great whites and similar species, including certain large tunas, find themselves navigating a precarious situation. They are caught in a 'double jeopardy' scenario, facing both rising temperatures and diminishing food supplies, primarily due to overfishing. Nick Payne, an associate professor at Trinity College Dublin and the lead author of the study, explains, "If you’re a shark, you can’t just pop down to the supermarket and buy more food. We’re seeing animals move with climate change in every biome on land and in the sea; this is just another example of that mechanism." From the powerful great whites of South Africa to the filter-feeding basking sharks off Ireland's coast, these mesothermic species expend nearly four times the energy of their cold-blooded counterparts. As ocean temperatures rise, they must adjust their behaviors—slowing down, altering their blood flow, or diving deeper to find cooler waters—all while struggling to secure an ever-scarcer food supply. Mesothermic fish, which include thresher and porbeagle sharks, represent a rare group that retains metabolic heat to keep their bodies warmer than the surrounding water. This adaptation has historically been crucial for their speed and ability to hunt. However, as they grow larger, the heat they produce exceeds their capacity to dissipate it, leading to significant risks of overheating in warmer waters. While some species, like the Atlantic bluefin tuna, can temporarily increase their heat loss or dive to cooler depths, the available habitats for mesothermic species are shrinking. This trend is likely to intensify during summer months, leading to heightened competition for dwindling prey resources.