Oceans warm. Great white sharks feel it first in their cores. These mesothermic marvels—less than 0.1% of marine life—retain metabolic heat to outpace prey, strike harder, roam farther. But that edge flips to peril as global temperatures climb. A one-ton shark hits its limit above 62.6 degrees Fahrenheit. Overheat looms. Habitats shrink. Food fights intensify. Researchers tracked it with pinpoint sensors. Tiny devices on basking sharks topping three tons revealed hidden heat budgets: production versus loss in real time. Mesotherms burn nearly four times the energy of cold-blooded kin at matching sizes and temperatures, according to a Science study led by Nicholas Payne of Trinity College Dublin. “The results were really quite striking—after accounting for body size and temperature, we found that mesothermic fishes use about 3.8 times more energy than similarly sized ‘ectothermic’, or ‘cold-blooded’ fishes,” Payne said. A 10°C rise more than doubles routine metabolic rate. Sharks can’t shop for calories.…