Selection for Tuskless Elephants

This video follows Joyce Poole and other scientists working in Gorongosa National Park, Mozambique, who made the striking observation that many female elephants lack tusks.

Most African elephants have tusks, but some — about 2% to 6% of females and even fewer males — never grow them. Elephant tusks are important for obtaining food and water, and essential to male elephants for competing for mates, so one might expect strong natural selection for having tusks. But the proportion of tuskless elephants has increased in some populations.

In this video, Poole explains a possible reason. Elephants with large tusks are targeted by poachers, who sell the tusks on the ivory market. Poaching is selecting for tuskless elephants, which are more likely to survive, mate, and pass on their genes. In Gorongosa National Park, Poole found that among the older female elephants that survived a period of heavy poaching in the park, over 50% are tuskless. Among the younger females, who were born after this period of heavy poaching, 33% are tuskless. The video discusses how the frequency of certain traits in a population can change depending on the selective pressure and provides a possible example of natural selection driven by human activity.

An audio descriptive version of the film is available via our media player.