An evolutionary advantage may be turning into a climate liability
Great white sharks built their success in part on a rare physiological trick: they can keep their bodies warmer than the surrounding seawater. That heat retention helps support speed, hunting performance, and long-distance movement. But as ocean temperatures rise, the same trait may become a growing vulnerability.
According to a new report in Science described by Ars Technica, great whites and other so-called mesothermic fishes could face increasing risk of overheating in warmer waters. The concern extends beyond individual animals. These species often occupy top positions in marine food webs, which means changes in their range or performance could ripple outward through entire ecosystems.
The finding sharpens a broader climate story. Warming does not affect all marine animals equally. Species with unusual metabolisms, large bodies, and high energy needs may hit physiological limits earlier than others, particularly when food supplies are also under pressure.
Why warm-bodied fish are different
Most fish are effectively cold-blooded, with body temperatures that track the surrounding water. Mesothermic species differ because they retain some internally generated heat. The group is rare, representing a tiny fraction of marine life, but it includes ecologically and commercially important animals such as great white sharks, basking sharks, thresher sharks, porbeagle sharks, and several tuna species.
That warm-body strategy comes with clear advantages. These animals can swim faster, sustain greater activity, and in some cases range across large distances while remaining effective predators or foragers. For apex predators like great whites, that physiology helped shape their place in the ocean over millions of years.
But the same system is energetically expensive. The report says mesothermic fishes burn far more energy than their cold-blooded counterparts. As seawater temperatures rise, the gap between heat generation and heat loss becomes harder to manage, especially in larger animals whose bodies trap heat efficiently.
In simple terms, they may run too hot in conditions that once supported them.
The double pressure of heat and hunger
The study points to a “double jeopardy” for these species. They need substantial energy to maintain their elevated body temperatures, yet warming oceans are arriving alongside declines in food availability driven in part by overfishing. That combination can squeeze animals from both directions: their physiological costs rise even as prey becomes harder to find.
Lead author Nick Payne of Trinity College Dublin told Inside Climate News that sharks cannot simply compensate by finding extra food on demand. That matters because climate stress is rarely one variable at a time. For marine predators, temperature, prey access, competition, and movement all interact.
Some species may partially cope by diving into cooler water or altering blood flow to shed more heat. But those strategies have limits. Seasonal warming, especially in summer, could make larger stretches of habitat unsuitable, forcing animals into narrower thermal refuges where competition for prey may intensify.
For great whites, whose cultural image often obscures their biological constraints, this is a reminder that apex status does not guarantee resilience.
Range shifts could reshape marine ecosystems
When top predators move, ecosystems move with them. If mesothermic sharks and tuna are pushed toward cooler waters, the changes will not stop at their own distribution maps. Predation pressure can rise in some areas and weaken in others. Prey communities may respond. Fishing industries may also see shifting stock patterns and altered management challenges.
The source text notes that these species exert disproportionate control on organisms below them in the food web. That makes them especially important from an ecosystem perspective. A climate-driven retreat or redistribution of great whites, bluefin tuna, or basking sharks would not be a niche biological story. It would be a structural change in how parts of the ocean function.
There is also a geographical dimension. Areas that currently support iconic predator populations may become less favorable during hotter periods, while cooler regions may see new overlap among species competing for similar prey resources.
What the report changes
Climate discussions about marine life often focus on coral bleaching, species moving poleward, or acidification. This report adds a more specific physiological warning: some fish may be threatened not only by habitat change, but by their own heat-management strategy under warmer baseline conditions.
That distinction is important because it suggests vulnerability is built into the mechanics of how these animals operate. The very feature that made them formidable in cooler seas may narrow their options in hotter ones.
It also complicates conservation. Protecting sharks cannot stop at reducing fishing pressure or preserving migration corridors if the thermal envelope of viable habitat is shrinking. Management will have to account for climate exposure, prey distribution, and the changing geography of suitable water temperatures.
Why this matters beyond sharks
Great white sharks draw attention because they are famous. The bigger lesson is that climate change can invert long-standing ecological advantages. Traits that evolved under one set of ocean conditions may become liabilities under another. Mesothermic fishes are an especially vivid example because their bodies sit at the edge between cold-blooded and warm-blooded strategies.
The report does not suggest these species will vanish overnight. It does suggest the rules governing where and how they thrive are changing. For animals already dealing with fishing pressure and reduced prey availability, that is a consequential warning.
As the oceans continue to warm, the emerging question is not just whether marine species can move. It is whether their physiology can still keep pace with the world they are moving through.
This article is based on reporting by Ars Technica. Read the original article.
Originally published on arstechnica.com
