Some elephants are evolving to have no tusks as a response to poaching

An elephant's tusks are among its defining features, but an increasing proportion of female elephants in Mozambique's Gorongosa National Park have been born without these crucial tools, and scientists say it's an evolutionary response to poaching.

But an increasing proportion of female elephants in Mozambique's Gorongosa National Park have been born without these crucial tools, and scientists say it's an evolutionary response to the brutal killing of elephants for their ivory tusks during the country's 15-year civil war.

Elephant experts working in the park had begun to notice the phenomenon after the war ended in 1992. Field data and analysis of old video footage from the park found that the proportion of tuskless female elephants increased more than threefold between 1972 and the year 2000. It was a period during which the elephant population plummeted from roughly 2,000 to about 250 individuals, said Ryan Long, an associate professor of wildlife sciences at the University of Idaho.

"During the war, Gorongosa was essentially the geographic center of the conflict," Long said via email. "As a result there were large numbers of soldiers in the area and a lot of associated motivation... to kill elephants and sell the ivory to purchase arms and ammunition. The resulting level of poaching was very intense."

Scientists now have a better understanding of the genetic basis for this tusklessness and why it only appears to affect female elephants, according to a study that published in the journal Science on Thursday.