The bigger their brains are, the faster they fall off the face of the Earth and become extinct. That’s the word from a new study which found that mammals with larger brains face a greater risk of extinction than those with small ones. If that doesn’t make you check your hat size, it should.
Eric Abelson, research wildlife biologist at the Pacific Southwest Research Station of the U.S. Forest Service, studied 1679 individual animals representing 160 species of mammals in North and South America ranging in size from mice to buffaloes (the study did not include water mammals). Since larger animals generally have larger brains, he instead focused on the ratio of brain size to body size. The results of his research, released in the current edition of Proceedings of the Royal Society B, were shocking.
For the past 40 million years, carnivore species with larger relative brain sizes were less likely to become extinct, but in mammalian species alive today, we find the opposite trend. Modern mammals with large relative brain sizes are more likely to be endangered rather than less.
Abelson found that large-brained mammals such as the short-eared dog (Atelocynus microtis), tiger cat (Leopardus tigrinus) and pygmy raccoon (Procyon pygmaeus) were listed as near threatened to critically endangered. Brains don’t equate to brawn against extinction as the smart Channel Island fox (Urocyon littoralis) is also near threatened.
The bad news for big brains held true when Abelson looked at other species outside the Americas and found big-brained animals at the top of the endangered lists, especially smaller animals with relatively larger brains.
Why don’t brains equate to smarts when it comes to fighting extinction? Blame the big brain, says Abelson. Large brains require more food, so the scarcities caused by environmental changes and human encroachment put those with big hungry brains under greater pressure. You can’t out-think drought, excessive heat or bulldozers.
While Abelson’s research won’t help animals stave off extinction, it will help identify those in danger.
Understanding the role that relative brain size plays in endangerment risk might give us another tool to identify the animals that might face trouble down the road.
Human brains aren’t the biggest in size or proportion to body size and we’re probably the smartest mammals. But, if our actions cause those ahead of us to become extinct, we’ll be at the top of the list one day too.