Ivory hunting makes elephants evolve

Mathilde Fontez, editor-in-chief of the new scientific magazine Epsiloon tells us today about a study carried out in Mozambique on a population of elephants who live in the Gorongosa National Park, and which would lose their ivory tusks.

franceinfo: Researchers have discovered that ivory hunting changes elephants: are they born without tusks?

Mathilde Fontez: Yes, elephants without tusks. This is a study that has just been conducted by biologists at Princeton University. They looked in particular at a population of elephants, which lives in Gorongosa National Park, Mozambique. And they realized that since 1995, 33% of females have been born defenseless, up from 18% in the 1970s.

And is it the man who would be responsible for that?

This is what the researchers establish. This park is a textbook case. Because elephants were particularly under the pressure of ivory hunting there, during the civil war between 1977 and 1992. At the time, poaching intensified. So much so that the elephant population has fallen by 90%. It went from 2,500 animals to only 200 in the early 2000s. Today, the population is in the process of rebuilding itself. But with an imbalance: elephants without tusks were selected.

What happened is actually very simple: Elephants without tusks were five times more likely to survive. They were therefore able to perpetuate themselves, and they transmitted their genetic peculiarity to their descendants.

But does this only affect females?

Yes. This is what prompted the researchers to conduct a genetic study, to complete their statistical modeling. They studied the genes of 18 elephants, and they found two mutations, on their X chromosome. These mutations would be responsible for this disappearance of the defenses. Moreover, we know these genes in humans, we know that they are involved in the growth of the incisors. So everything fits.

And what they also found is that when these mutations are passed on in the male elephant, they are fatal. A defenseless male elephant cannot be born with this mutation. There are therefore fewer births, and fewer males. This means that even if the elephants are no longer hunted in the park, the population will have difficulty in recovering.

Is this the first time that we have observed such a change, so rapid in a population?

It has already been shown that hunting can cause rapid changes in animals. For example, we have seen the size of the horns of the bighorn sheep decrease by 20%… But this is a complete study. We see natural selection taking place before our eyes, down to the genes themselves.

And then it’s the elephant: it’s emblematic. And it plays a major role in its entire ecosystem, through the plants it eats for example. Researchers have also seen that elephants without tusks do not choose the same plants. Their multiplication could therefore also change the landscape.