Relative brain size as a predictor for mammalian extinction vulnerability

Background/Question/Methods

Global anthropogenic pressure on wildlife is continuing to mount leaving conservationists faced with finding salient characteristics that predict population decline in mammals. Confounding the ability to preserve mammalian species is the complexity of traits and behaviors that influence their ability to thrive in changing landscapes. The brain is the seat of information processing, storage and the origination of behaviors yet the importance of neural physiology to conservation is poorly understood. Many prior studies have found links between increased relative encephalization (RE; brain size corrected for body size and phylogeny) and an increase in traits that are believed to support increased ability for survival. However, there has not been a study that has examined the relationship between brain size and conservation status. To address this gap in knowledge I examined the relationship between RE and conservation status in modern mammals and in carnivores over the last 42 million years. To this end I generated a database of brain and body size for over 160 modern mammalian species from the Americas. Additionally, I compiled brain size data for 200 mammals that have lived over the last 42 million years and examined the relationship between brain size and extinction.

Results/Conclusions

Preliminary results using a Cox Proportional Hazard model, for carnivores over the last 42 million years, suggest that species with larger RE have a significantly reduced risk of extinction during an extinction event when compared to species with smaller RE (n=200 species). Additionally, in modern mammalian species, as RE increases probability of being endangered decreases. These results underscore the importance of including RE in work examining extinction risk in mammals.