Elephants are evolving to not grow their tusks after years of being hunted and killed by poachers, research reveals.

Almost 90 per cent of African elephants in Mozambique's Gorongosa National Park were slaughtered for their ivory to finance weapons in the country's civil war.

But around a third of females - the generation born after the war ended in 1992 - have not developed tusks, recent figures suggest.

Elephants are evolving to lose their tusks to avoid being hunted and killed by poachers, research reveals

Almost 90 per cent of African elephants in Mozambique's Gorongosa National Park were slaughtered for their ivory to finance weapons in the country's civil war

Male elephant tusks are bigger and heavier, but due to increased poaching, hunters began to focus on females.

Joyce Poole, scientific director of a nonprofit called ElephantVoices, told the National Geographic: 'Over time, with the older age population, you start to get this really higher proportion of tuskless females.'

Other countries have also seen a shift in the number of elephants growing tusks.

In South Africa 98 per cent of the 174 females in Addo Elephant National Park reportedly did not grow tusks in the early 2000s.

Poaching has also cause the size of tusk to go down in some heavily hunted areas, such as southern Kenya.

Scientists say that the elephants with this handicap may be altering how they behave.

Tusks are used for digging water or getting bark of trees for food, so the mammals may be travelling further afield to find survive.

Scientists say that the elephants with this handicap may be altering how they behave

But researchers say changes in the way that elephants live could have larger implications for the ecosystems around them.

Ryan Long, a behavioral ecologist at the University of Idaho, told the National Geographic: 'Any or all of these changes in behavior could result in changes to the distribution of elephants across the landscape, and it's those broad-scale changes that are most likely to have consequences for the rest of the ecosystem.'

The number of tuskless elephants has indicated the lasting effect humans have had on animals.