Aliens With Big Brains

Biologists have fingered all kinds of reasons – from aggressive behavior to baby-making prowess – to explain why some species become successful invaders and others don’t. Now they’ve thought up another possibility: brain size. A survey reveals that, among amphibians and reptiles, successful invaders tend to have bigger brains than the failures.

Previous studies have suggested that invasive birds and mammals with big brains have an advantage when it comes to solving new problems, such as dodging unfamiliar predators or catching new prey. Three researchers at the University of Sydney in Australia – Joshua Amiel, Reid Tingley and Richard Shine – wondered if the same might be true for amphibians and reptiles too.

To find out, they collected data on brain and body mass for 149 species. Nearly half (72) had been introduced outside of their native ranges at least once, creating a pool of 561 “introduction events” in seven biogeographic regions. Then, they compared the relative brain sizes of the successful and unsuccessful invaders.

The big-brained aliens won out in six of the seven bioregions, they report in PLoSOne. “The exception (where relatively larger brains did not facilitate invasion success) was Australasia,” they note.

Overall, the findings suggest “that larger brain size enhances the ability to deal with novel environmental challenges.” But it isn’t clear whether that is because larger brains enhance cognitive (thinking) ability, or abilities like perception and motor skill. Another question is “whether invasion success is differentially associated with enlargement of specific parts of the brain… or with a general size increase.” And the fact that small-brained invaders did better in Australasia suggests that, sometimes, big brains can be a disadvantage, perhaps because big-brained species often need more food and energy to survive.

Given the looming reality of global change, however, they conclude that “an ability to cope with novel challenges may well prove to be one of the most significant predictors of species viability.” – David Malakoff | April 13, 2011

Source: Amiel, J., Tingley, R., & Shine, R. (2011). Smart Moves: Effects of Relative Brain Size on Establishment Success of Invasive Amphibians and Reptiles. PLoS ONE, 6 (4) DOI: 10.1371/journal.pone.0018277

Image © Ivan Mateev