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A female elephant without tusks stands by a watering hole
Photo:
OKAPIA KG;
Germany / picture-alliance / OKAPIA KG, Germany
When humans intervene in nature, it usually doesn't end well.
This has been shown again and again in the decline in insect populations or in the clearing of primeval forests, which massively restrict the habitat of animals and plants.
In Mozambique it is now becoming apparent how a genetic defect has penetrated elephants through humans, which actually means a disadvantage for the animals.
Intensive poaching during the civil war could have led to an increasing number of female elephants being born without tusks. This is what a team led by Shane Campbell-Staton from Princeton University (USA) writes in the science magazine "Science". Toothless elephants would have a survival advantage due to massive poaching - because without the valuable ivory tusks they are worthless to poachers.
For the study, the researchers examined African elephants. They live together in family-like herds and have no natural predators. Nevertheless, the number of animals in many regions of their range has decreased sharply. Overall, the population is considered to be endangered. Humans play an essential part in this: for centuries they have intervened in the natural habitat of elephants. Soldiers went to war on the elephants or killed them for a valuable commodity - ivory.
Elephants were also targeted during the civil war in Mozambique in the 1970s.
In Gorongosa National Park, soldiers killed the animals to get the ivory.
With the sale they financed ammunition and weapons.
The once dazzling national park was destroyed at the end of the war in 1992.
Around 95 percent of the big game fell victim to the war, and the elephant population also shrank to around a tenth.
According to the current study, this could have led to a rapid evolutionary development: In video recordings, Campbell-Staton's team first noticed that the proportion of tuskless female elephants had tripled after the civil war.
An accident?
The researchers write that it is unlikely.
Rather, the lack of the mighty tusks proved to be a survival advantage in wartime.
Without the ivory, the elephants were useless to the poachers, tuskless elephants survived and could continue to reproduce.
In this way, the animals also passed on the genetic change that is the basis for tusklessness.
In corresponding investigations, the researchers found changes in two genes that also play a role in tooth development in other mammals.
Why only elephant cows?
And why are only female elephants born without tusks? The researchers report that this is probably due to the fact that one of the genes is located on the X chromosome along with other vital ones. If genetic changes occur, female animals could compensate for harmful effects through their second X chromosome. Since males only have one X chromosome, the genetic changes lead to death during embryonic development. A corresponding clinical picture is known at least from humans.
The changed genome persisted long after the war: counts of animals born between 1995 and 2004 showed that more and more females were born without tusks.
This could not only harm the elephants themselves: With the help of the massive tusks, they can search deep in the earth for water and dig up trees.
In doing so, they create habitats and food sources for many other animal species.
There are still elephants in Gorongosa National Park.
It has been rebuilt since the end of the war and is open for tourist excursions.
The missing tusks of the animals are reminiscent of the fights that once took place here.
joe / dpa
