NAIROBI, Kenya: Poaching has longer-term effects on elephant populations than originally thought, new research has found. A pair of studies, published recently by researchers at Colorado State University and Save the Elephants (STE) shows that orphaned juvenile elephants have less chance of survival in a herd – and that losing them has a significant impact on population growth or decline.
Conservation efforts have traditionally been informed by “macro-scale” research of populations, says George Wittemyer, a conservation biologist at Colorado State who was the lead author of one of the studies. “If you really want to get more targeted actions, you need to know who in the population is driving increases or decreases in the population.”
Both studies did just that, examining decades of individual elephant data collected by Save the Elephants in Samburu National Reserve in northern Kenya. Taken together, the two papers show the damage done by poaching is severe and lasting.
Jenna Parker, a conservation biologist at Colorado State, was the lead author of a study published in, Current Biology that showed poaching adult elephants not only directly lowers population growth, but indirectly lowers it as well because surviving orphaned elephants have a lower probability of survival.
“For social populations, poaching has a larger impact than originally thought, because you have to account for the orphans who are left behind who are surviving less because they don’t have a mother,” Parker says.
Parker and her colleagues examined 20 years of individual based monitoring data collected by STE and compared survival of young elephants who were orphaned by poaching with those who were not. They found that orphans had lower survival probabilities, and that lowered orphan survival further exacerbated declines in populations caused by poaching. And when poaching was more frequent, the effect of orphan survival on these populations was greater. Even orphans who were no longer dependent on their mother’s milk had a lower survival rate than their peers with a living mother, the study found.
“The total impact of poaching is greater than was originally recognized,” Parker said. “In populations that we think have undergone a lot of poaching, even as the poaching slows we still need to consider its residual effects.”
The long-term effects of orphan survival are underscored by another study published by Wittemyer and STE colleagues in Ecosphere that analyzed how the survival or different age groups affects elephant population trends. Because older male elephants tend to reproduce more than younger ones, and older females are the leaders of family groups and social units, conservation biologists long assumed that the older age group was most important to population trends. But the study showed that’s not the case.
Wittemyer and his colleagues examined 20 years of monitoring data collected by STE on the same elephants and looked at how mortality at different ages impacted populations.
Juvenile elephants who are just starting to become independent of their parents are the most important to elephant population dynamics, says Wittemyer. “If they’re surviving well, the population is pretty buffered from decline. If they start to decline, then you’re in deep trouble.”
The data also showed that human activity — specifically, wounding or killing elephants — decreased survival of all ages in a population. “Even for calves, which we don’t think of as being targeted by humans for ivory, their survival was really strongly driven by human impact on the population,” Wittemyer explains. “Human impacts dominate anything else going on in the population in terms of affecting survival.”
The two studies highlight the impacts of poaching on elephant behavior, and in turn, on elephant demographics. “Killing an elephant is not removing one elephant from a population; killing an elephant has downstream effects on those elephants that are bonded to it,” he says. “These papers give us high-resolution information on elephant demographics that help us to better understand the decline and recovery processes of elephant populations.”
Key findings from the studies include:
- Orphan African elephants have a lower survival probability than non-orphans.
- Orphaning of wild African elephants decreases population growth.
- Orphan survival is more critical to population growth when there is more poaching.
- Poaching both directly and indirectly decreases population growth in elephants.
- During periods of low human impact, fertility is the most important factor driving population size
- During periods of high human impact, survival of young elephants is the most important factor driving population size
- Human impact is the single greatest factor affecting elephant survival and subsequent decline or increase of elephant populations
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About Save the Elephants
Based in Kenya, Save the Elephants works to secure a future for elephants. Specializing in elephant research, they provide scientific insights into elephant behavior, intelligence, and long-distance movements and apply them to the challenges of elephant survival. Education and outreach programs share these insights with local communities as the true custodians of this rich heritage. The team works towards a future of harmonious coexistence between humans and elephants. High-tech tracking helps plan landscapes while low-tech beehive fences, among other tools, provide farmers with protection as well as income. To battle ivory poaching, Save the Elephants teamed up with the Wildlife Conservation Network created the Elephant Crisis Fund to identify and support the most effective partners in Africa and in nations with ivory markets to stop poaching, thwart traffickers and end demand for ivory.