Size matters: preventing large mammal extinction

Saving large mammals such as elephant and rhino could be made more effective by focusing on individual species as well as their habitats.

“Conservation biologists have always known that large bodied mammals are at greater risk of extinction,” comments Professor Georgina Mace of the Institute of Zoology, “Now we understand the mechanisms, we are able to tailor conservation programmes dependant on size, to ensure they’re more effective.”

The study showed that extinction risk in smaller mammals, below approximately 3kg (about the weight of a small domestic cat), is determined primarily by the size and locations of their distributions, and the human impact to which they are exposed. Larger mammals have the additional pressure of biological disadvantages such as long gestation period and late weaning age to contend with, significantly increasing their chances of extinction.

“From a conservation policy angle, the message would be: small may be conservable but it is a little trickier for the larger mammals,” commented Dr Andy Purvis of Imperial College London who also contributed to the research.

Biological traits such as low population density, slow life history, late weaning age and extended gestation in mammals above a certain size means they are evolutionarily disadvantaged in the face of human impact, compared to species of smaller size.

The study suggests smaller species, of around less than 3kg, would benefit from conservation of their habitat area, whereas, large mammals need a more complex conservation strategy, which takes into account their biology in combination with the external threats they face.