WASHINGTON (AP) – Elephants typically benefit from having tusks, which help them access water, strip bark for food, and engage with other elephants. However, during intense ivory poaching, these tusks can become a disadvantage.
Recent research has uncovered how years of civil conflict and poaching in Mozambique have resulted in many elephants born without tusks.
From 1977 to 1992, the region now known as Gorongosa National Park experienced a catastrophic decline in elephant populations due to poaching, with nearly 90% of elephants killed for ivory to fund war efforts.
Among the few elephants that survived, a significant proportion lacked tusks. Before the conflict, only about 20% of female elephants were tuskless, and half of the surviving females were naturally born without them.
Similar to how eye color is inherited in humans, the presence of tusks in elephants is determined by genetics.
What was once a rare trait among African savannah elephants has become increasingly prevalent, akin to a once uncommon eye color becoming widespread.
Following the war, tuskless females passed their genes to their offspring, leading to some expected and some surprising results.
Approximately half of their daughters were tuskless, while two-thirds of their offspring were female. Evolutionary biologist Shane Campbell-Staton of Princeton University noted that the events of the war “changed the trajectory of evolution in that population.”
Campbell-Staton and his colleagues published their findings in Science on Thursday to explore how poaching influenced natural selection.
Researchers, including biologists Dominique Goncalves and Joyce Poole, studied around 800 elephants in the national park over several years, cataloging mothers and their young.
Poole, co-founder and scientific director of the nonprofit ElephantVoices, explained that female calves tend to remain close to their mothers, with males doing the same until they reach a certain age.
She observed similar patterns in other regions, like Uganda, Tanzania, and Kenya, where intense poaching led to higher numbers of tuskless females.
In Gorongosa, the research team collected blood samples from 11 tuskless and seven tusked female elephants, analyzing their DNA for differences.
Because tuskless elephants are female, they concentrated their study on the X chromosome, which females have two of, while males have one X and one Y chromosome.
The researchers suspected that the gene responsible for tusklessness is dominant, meaning a female only needs one altered gene to exhibit the trait.
However, when this gene is passed to male embryos, it may hinder their development, possibly leading to early miscarriages.
Brian Arnold, an evolutionary biologist at Princeton and co-author of the study, noted, “When mothers pass it on, we think the sons likely die early in development.”
Their genetic analysis identified two key regions in the elephants’ DNA that were believed to influence tusklessness. These genes are also linked to tooth development in other mammals.
Chris Darimont, a conservation scientist at the University of Victoria, emphasized the significance of this research, stating, “They’ve produced the smoking-gun evidence for genetic changes,” illustrating how human actions can dramatically impact the evolution of other species.
Traditionally, evolution is perceived as a slow process, but this study shows that humans can accelerate it significantly.
Samuel Wasser, a conservation biologist at the University of Washington, commented on the speed of these changes, noting that “the fact that this dramatic selection for tusklessness happened over 15 years is one of the most astonishing findings.”
The scientists are now investigating the implications of having more tuskless elephants for the species and their savannah habitat.
Preliminary analyses of fecal samples indicate that these elephants are altering their diets due to the absence of tusks, essential for peeling bark from trees.
Robert Pringle, a biologist at Princeton and co-author, stated, “The tuskless females ate mostly grass, whereas the tusked animals ate more legumes and tough woody plants,” suggesting that these dietary changes will persist for several generations.
This research sheds light on the profound effects of poaching on elephant evolution and highlights the urgent need for conservation efforts to protect these magnificent creatures.
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