New Study: After Years of Poaching, Elephants Change Their Evolutionary Trajectory

Poaching has long been a threat to African elephant populations. During Mozambique’s civil war—a two-decade period from the 1970s to the 1990s—the number of elephants in Gorongosa National Park declined by 90 percent. As a result of this ivory hunting and relentless poaching of ivory, the number of elephants in the park dropped to just 200 in the early 2000s.

However, a new study in Mozambique, focusing on elephant populations in Gorongosa National Park, illustrates the evolutionary impact of poaching. More and more elephant elephants are now being born without tusks – a change that will affect the ecological landscape of Gorongosa National Park and the future of the species.

While poaching is now illegal in Gorongosa National Park, its impact on elephant populations and the region is clear and will continue to be so for years to come.

tuskless elephant

Before the Mozambican civil war, only 18.5 percent of female elephant elephants had no tusks. Now, after 91 female births, that number has risen to 33%. After analyzing mathematical models of other evolutionary traits, researchers at Princeton University in New Jersey determined that the rise of edentulous descendants was directly linked to the effects of poaching. Because elephants are selectively hunted for their tusks, a large proportion of genetically tuskless elephants in the region survive to reproduce, compared to historical trends.

The transition from tusk-like to tuskless elephants is an important transition for a number of reasons:

• First of all, only the matriarch can be without tusks. The toothless trait is actually a genetic mutation on the X chromosome and is therefore fatal to male elephants.
• Second, tusked and tuskless elephants ate different plants. As the number of tuskless elephants increases, changes in elephant eating habits will have widespread ecological impacts across the region. Elephants are keystone species, meaning changes in their diet will have a trickle-down effect on all other species in Gorongosa National Park.
• Third, since only female elephants would be able to survive without tusks, the elephant population would have a lower overall birth rate. Without males, fewer babies are born, causing the species to recover more slowly than researchers first hoped.

While the absence of tusks is an advantage in the face of poaching and the human war for ivory, its impact on the species could be enormous. This seems like a good thing: Evolving quickly to a toothless state to avoid being killed by poachers may actually have negative long-term effects.

It only takes one copy of the tuskless gene mutation to be lethal to a male baby elephant. As this gene becomes more dominant due to rapid evolution, fewer male elephants will be born, eventually causing the species to decline even more than poaching initially reduced.

rapid evolution

Humans dominate the ecological evolution of the earth. Elephants are not the only examples. Humans have caused a variety of animal species to undergo “rapid evolution”.

Rattlesnakes have begun to shrink due to more human interaction in South Dakota. This is because rattlesnakes have a higher mortality rate when spotted by humans who hear the rattlesnake.

Bighorn rams in Alberta, Canada, are shrinking. Horn size has decreased by 20% due to trophy hunting in the region.

Rats and bedbugs have developed resistance to insecticides. Due to rodent control, these species have adapted new ways of surviving among exterminators. By evolving to become resistant to pesticides, rats and bedbugs are challenging human interference.

What we as humans need to understand is our impact on these other life forces. What we do directly impacts the animals on our planet. Rapid evolution doesn’t just affect elephants, bighorn sheep, mice or rattlesnakes; their adaptations will eventually affect us as well. So, maybe, we should keep an eye out for them now.