- The civil war that caused elephant numbers to drop sharply in Mozambique’s Gorongosa National Park has also led to the absence of tusks becoming the norm among its female elephants, according to a recent study.
- Only about 200 of the roughly 2,500 elephants that live there survived the ravages of the 15-year war in which poachers targeted tusked elephants for ivory.
- After the civil war, the number of defenseless females tripled in Gorongosa.
- Scientists agree on the profound consequences of this “artificial selection,” but how the genetic trait is passed down from generation to generation is still under investigation.
Mozambique‘s 15-year civil war has changed the face of its national parks, which have suffered widespread poaching of large mammals, including elephants.
He did a lot more. He changed the face of female African savanna elephants (Loxodonta africana). The unusually high number of defenseless females in Gorongosa National Park today can be attributed to the ravages of this war, which raged from 1977 to 1992, a recent study in the journal Science shows.
For Dominique Gonçalves, elephant ecologist in Gorongosa, the altered profiles of his favorite animal are profound. She was born 29 years ago when the country emerged from conflict, and seeing the scars of that looting spread into the present is sobering. Poachers targeted elephants with tusks, carriers of precious ivory that could be exchanged for weapons. Only about 200 of the approximately 2,500 elephants in the park survived the massacre.
“It’s in our faces, we did it,” said Gonçalves.
In the new article, Gonçalves and a team of researchers from the US and UK describe how wartime slaughter continues to shape the herd today. “Poachers preferably killed animals with tusks and let those without tusks survive, so they reproduced and produced more offspring without tusks,” Gonçalves said. “We have selected them artificially. “
Elephants are the largest living terrestrial beings, an ancient species that has roamed the planet for over a million years. Tusks also adorned their ancestors, persisting because of their usefulness. Defenders use them to tear bark from trees, dig in dry soil to find water, and sometimes to push or rescue stray youth. Male elephants, with larger tusks than females, wield them in combat and to attract mates.
An exception is helpless elephants, a trait that appears almost exclusively in females. But even then, only two in every 100 female African elephants are born without tusks. After the civil war, the number of defenseless females tripled in Gorongosa.
Genetics and environmental pressures interact to determine whether a trait is passed from generation to generation. One of the objectives of the study was to determine which slices of elephant DNA encode the absence of tusk.
The researchers examined the genome of tusked and tusked elephants, hoping to uncover the critical anomaly, and narrowed it down to two candidates located on the X chromosome. This is a dominant gene, so even if the offspring receive a copy from either parent, they can exhibit the trait.
That still didn’t explain why so few male elephants are defenseless. In males, the absence of tusks is often linked to injury; it is not congenital. The study’s authors landed on one possible explanation: this is a lethal male trait. A mother can pass it on to a daughter, but if a male embryo carries it, the pregnancy likely ends in a miscarriage.
Yet the puzzle of the lack of defense is far from resolved.
“This is an interesting article, exploring the difficult question of the genetic basis for the lack of tusks in elephants,” Anna Whitehouse, an elephant expert based in South Africa who has studied elephant populations in the Addo Elephant National Park of this country.
Addo has fewer females with tusks, less than 10%. Over the decades, the lack of tusks has become more prevalent in the population.
Whitehouse said Addo’s inheritance model did not support the assumption made in the new document. According to the new study, daughters of tusked mothers should all have tusks, she said. But the Whitehouse team did not observe this in Addo, where four tusked hens produced eight hens, all defenseless.
“I am currently working with Addo Elephant National Park to understand the genetic basis for the lack of tusks in this population, but at this time it remains a mystery,” said Shane C. Campbell-Staton, evolutionary biologist. at Princeton University and first author of the Science paper.
What is clear is that the tusks make their owners the targets of poaching, which continues to threaten African elephants. Between 2010 and 2015, Mozambique alone lost nearly 10,000 elephants, or half of the population, mainly due to highly organized poaching.
This year, IUCN, the world conservation authority, officially recognized for the first time that the African elephant is in fact two distinct species: Africa’s smallest forest elephant (Loxodonta cyclotis) and the African savanna elephant. Both are in danger. The population of savannah elephants has declined by 60% over the past half century.
The IUCN assessment cited habitat loss as a critical reason for the decline. Reclaiming lost ground will require more than just bouncing back the numbers. Savannah elephants occupy only one tenth of their historic range in Gorongosa. A swollen herd confined to a small area can have problems with humans.
And their numbers, at least in Gorongosa, have increased from 200 to around 1,000 today. “They can come back with the right time, space and protection,” Gonçalves said.
While elephants may return, it’s unclear whether tusks will make a comeback. Losing that trait could have wider consequences, Gonçalves said.
By distorting their evolution, humans also play with the role of elephants in the ecosystem. These giant foragers are master engineers of their environment. As long-distance animals, they shape vast swathes of wilderness, trample and gnaw on them, fight with trees, rearrange foliage. The lack of defense takes away one of their trusted tools and can ultimately change the floral and wildlife composition of their surroundings.
“It’s funny, isn’t it, we are impacting their appearance now, but it’s going to come back to affect us somehow,” Gonçalves said.
Campbell-Staton, SC, Arnold, BJ, Gonçalves, D., Granli, P., Poole, J., Long, RA and Pringle, RM (2021). Ivory poaching and the rapid evolution of the absence of tusks in African elephants. Sciences, 374(6566), 483-487. do I:10.1126 / science.abe7389
Whitehouse, AM (2002). Lack of defense in the elephant population of Addo Elephant National Park, South Africa. Journal of Zoology, 257(2), 249-254. do I:10.1017 / s0952836902000845
Malavika Vyawahare is the Malagasy editor of Mongabay. Find her on Twitter: @MalavikaVy
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