Elephants evolve to beat poachers

Intensive ivory poaching has been linked to an increase in the number of tuskless elephants in Mozambique, which probably adapted to survive, a new study published in the journal Science has found.

The study, centred in the Gorongosa National Park in Mozambique, concluded that the sharp decline in the country’s elephant population caused during the Mozambican civil war from 1977 to 1992, when both sides engaged in animal poaching, was accompanied by an increase in the survival rates of tuskless elephants.

‘‘Intensive poaching in Africa has been associated with an increase in the frequency of tuskless elephants, exclusively (or nearly so) among females,’’ the study said.

It noted that there was no record of tuskless male elephants in the park.

The sharp decline in the Gorongosa elephant population during the war – up to 90 per cent – was accompanied by ‘‘a nearly threefold increase in the frequency of tuskless females’’, from 18.5 per cent in 1970 to 50.9 per cent in 2000, the study said.

The population of tuskless elephants then declined, to 33 per cent by 2010.

The absence of tusks is caused by a mutation in the X chromosome in elephants that is lethal to males, according to the study. The exact genetic mechanism that leads to tuskless elephants and its absence among males is still unresolved.

The changes in the elephant population at the Gorongosa National Park show ‘‘how a sudden pulse of civil unrest can cause abrupt and persistent evolutionary shifts in longlived animals, even amid extreme population decline’’, the researchers said.

A recovery in the numbers of elephants and tusks ‘‘may be crucial for ecosystem restoration’’, the study said.

Elephants use their tusks as tools to dig for water, strip bark from trees for food, excavate minerals and salts, carry loads, defend themselves, and battle other elephants, among other uses.