How do you tell two species apart? Let’s say you’re investigating a bird with two populations. One lives in the savanna, the other in the forest.
The savanna population eats grasshoppers, but the one in the forest eats beetles. The savanna bird is big-bodied with a curvy beak; the forest bird is smaller with a straighter beak.
Is this enough to determine you’re dealing with not one, but two species? Probably. But how about you look at the genetics?
Lo and behold, the animals’ DNA shows that the birds have been separated by 6 million years – easily making it two species.
Now, let’s say we’re not talking about birds here, but elephants. African elephants. Suddenly, things get messy. Really messy. And political. And heated.
“To my knowledge, all the evidence, now a very large amount, supports two [African elephant] species, and no evidence supports one,” said Nick Georgiadis, a research scientist with the Puget Sound Institute and a co-author of a recent paper that argues for two species published in the Annual Review of Animal Biosciences.
“There never was any objective evidence supporting one species, just a few subjective preferences that became dogma.”
But governments and the general public still accept just one species of African elephant, largely represented by the savanna elephant – the world’s biggest land animal. Even the biggest conservation players – including the International Union for Conservation of Nature (IUCN) and the Convention on International Trade in Endangered Species (CITES) – only acknowledge one species.
But Georgiadis and a growing amount of evidence – both morphological (physical) and genetic – points unquestionably to two: the savanna elephant (Loxodonta africana) and the long-ignored, far-more-endangered forest elephant (Loxodonta cyclotis).
Found in the rainforests of Central and western Africa, forest elephants are smaller than their savanna cousins and sport straighter tusks. They also live in smaller family groups than savanna elephants and have a very different diet, with a penchant toward fruit when available. Although poachers have decimated both groups in the last decade, forest elephants have been much harder hit. According to scientists, poachers slaughtered 65% of the world’s forest elephants in just 12 years.
“At least a couple of hundred thousand forest elephants were lost between 2002-2013 to the tune of at least sixty a day, or one every twenty minutes, day and night,” said Fiona Maisels head of the forest elephant study with the Wildlife Conservation Society in 2014. “By the time you eat breakfast, another elephant has been slaughtered to produce trinkets for the ivory market.”
Yet conservation efforts have been largely tilted, even now, towards the more famous savanna elephant. Currently there is a massive effort underway – known as the Great Elephant Survey – to survey the continent’s savanna elephant populations. But no similar large-scale conservation effort is focusing on forest elephants. By inhabiting rainforest landscapes, for elephants are much more difficult to survey or study. But they also may suffer from the fact that conservationists simply don’t view these animals as distinct.
“By not recognising two species…organisations may be condemning the African forest elephant to extinction,” said Alfred Roca with the Carl R. Woese Institute for Genomic Biology at the University of Illinois and the lead author of the recent review paper.
Still, many influential conservationists say there’s not enough evidence for two species. For example, WWF considers the forest elephant a subspecies and not a full species in its own right.
“While there are differences between elephants in the central African rain forests and eastern Africa it is impossible to define where an elephant becomes a forest elephant or a savannah elephant,” said Andrew McVey, the East Africa Regional Manager at WWF-UK, adding that “there is no clear definition on what a forest elephant is.”‘Multiple independent lines of compelling evidence’
Despite being one of the most familiar animals on the planet, there had been very little rigorous research on African elephant taxonomy until the last fifteen years. In 1900, German zoologist, Paul Matschie, was the first to suggest that the forest elephant was distinct species, granting him the honour of naming it: Loxodonta cyclotis. But at the time he thought there may be as many as 30 species or subspecies of African elephants. In 1928, Fernando Frade, a Portuguese naturalist, suggested two species: the savanna and the forest. The debate strung along into the 1930s, “but with no real evidence,” according to Georgiadis.
When the debate finally died down, scientists stuck to just one species. Then a paper in 2000 – a hundred years after Matschie’s work – finally provided some hard evidence.
Georgiadis called it “shocking” that the “very first systematic analysis” was so long in coming.
Led by UK zoologist Peter Grubb – who passed away in 2006 – the study examined 295 different skulls of African elephants. Grubb and his team found several distinct physical differences that split forest and savanna elephants, including body size, tusk shape and differences in both the cranium and the mandible.
But since the paper was published in an “obscure journal” according to Georgiadis, it was largely ignored. Another year would go by before the big news on forest elephants hit the scientific community. In 2001, Alfred Roca and colleagues published a landmark paper on elephant genomics in Science, which found distinct genetic differences between forest and savanna elephants.
A series of papers over the last few years have solidified the genetic findings and Roca said that now the best data points to forest and savanna elephant species splitting 5-6 million years ago. This is around the same time that woolly mammoths split with Asian elephants, and humans split with chimps.
Georgiadis dubbed these “multiple independent lines of compelling evidence” for two distinct species in Africa – and zero evidence for just one.
But the situation gets complicated when you add in the fact that sometimes savanna and forest elephants meet – and love blossoms. The offspring of these illicit affairs – the savanna-forest hybrid – not only survive, but also, at least in some cases, reproduce.
“Some still hold that ‘good’ species don’t hybridise,” said Georgiadis.
The hybrid problem
Experts have recognised for over a century that savanna and forest elephants are capable of mating and producing hybrids. This was – and still is – one of the key reasons why so many refuse to recognise forest elephants.
“They can interbreed and produce viable offspring,” said Julian Blanc with the CITES Program for Monitoring the Illegal Killing of Elephants (MIKE). “There are known areas of hybridisation, such as Garamba National Park in the Democratic Republic of the Congo. There are also known cases of savanna elephants living in forests (e.g. in Mount Kenya, Kilimanjaro and the Aberdare range), and forest elephants living in savanna (e.g. in savanna areas of Gabon).”
Yet, according to genetic evidence, hybrid mating is almost entirely one-sided. Forest elephant females mate only with savanna elephant males and rarely, if ever, do forest elephant males succeeding in wooing a savanna elephant female. The researchers believe this is because big is better in elephant mating.
“Paternity analysis in wild savanna elephants has shown that, when competing for mates, body size matters: large males produce more offspring than small males,” explained Georgiadis. “The same should apply to an even greater degree where both species coexist, since savanna elephants are much larger than forest elephants. For the same reason, savanna males would do most of the mating with hybrid females, and so on, ad infinitum.”
This means, over several generations, that forest elephant nuclear DNA (which makes up 99% of the genome) decreases in descendants of the hybrids until it vanishes altogether, as the genes are literally bred out.
So how do we know the elephants are hybridising? Even after the nuclear DNA signature of forest elephants is erased, mitochondrial DNA remains because this type of DNA is inherited only along the female line. In other words, savanna elephants may still retain the forest elephant mitochondrial DNA from a mating with a female that occurred hundreds of years before.
“’[Mitochondrial DNA] gets passed on from mother to daughter ‘forever,’” noted Georgiadis.
While detractors point to the hybrid situation as a reason to dismiss forest elephant, reproductive hybrids aren’t that uncommon in other species. For example, most animals in the canid family – like wolves and coyotes – can not only produce hybrids, but produce fertile ones. Many duck species in the Anas genus do the same. Even female mules are sometimes capable of bearing offspring. And perhaps, the most famous hybrid is a case from our own past: when humans and Neanderthals mated and bred – albeit with significant, but not wholly insurmountable, fertility challenges.
According to forest elephant expert John Hart, hybrid elephants are not taking over African anytime soon.
Ignorance of what is happening to forest elephants has not served them well. John Hart
“Hybrids are known only from specific areas, and contact with the two forms has not resulted in a hybrid zone across what is currently the forest-savanna boundary…This suggests that the two forms are mainly physically and reproductively separated,” said Hart with the Lukuru Foundation and the TL2 Project in the Congo.
But Blanc said that defining forest elephants as distinct species might solve one question, but would lead to new problems.
“There are many…places, especially on the interface between forest and savanna, and in much of West Africa, where we simply do not know whether we’re dealing with forest elephants, savanna elephants or hybrids. So a split would mean that the gaps in our knowledge on the status of the species would become even greater than they already are.”Conservation implications – are there any?
Those that advocate against splitting the species are currently winning the debate, at least on the ground. Whether or not they are correct, most of the heavy-hitters in conservation – the Wildlife Conservation Society (WCS) excluded – haven’t supported raising the status of forest elephants to full species. Moreover, these organisations also tend to argue that recognising forest elephants wouldn’t change much in conservation.
“There is limited conservation value in doing this,” said McVey with WWF. “Elephant conservation is already highly polarised in Africa and this would only further divide nations on elephant conservation.”
But those who advocate for the split disagree.
“Ignorance of what is happening to forest elephants has not served them well,” said Hart. “Major poaching of some populations has happened with scarcely any ripple of this coming out of the forests. “
Roca and his team point to the IUCN Red List, which last updated the African elephant in 2008. The Red List found that the African elephant population was ‘increasing’ and Vulnerable. But if scientists had evaluated the forest elephant separately, they would have certainly listed it as decreasing and likely set it in a higher category than Vulnerable, such as Endangered or Critically Endangered.
“It’s like saying, ‘We increased the lion population, which will more than make up for the fact that tigers are going extinct,’” said Roca, who noted these two great cats also split around the same time as forest and savanna elephants.
Moreover, even as Africa has faced a horrendous poaching crisis over the last eight years, there are still savanna elephant strongholds. For example, the Great Elephant Census recently estimated 129,000 savanna elephants in northern Botswana, a population currently free from poaching. But there are no equivalent population strongholds for forest elephants. Gabon is suspected to house around half the world’s forest elephants now, but even here the species has been widely poached out.
Georgidias said one of the reasons behind the continuing reluctance to split the species may be a desire to protect Africa’s elephants generally. If the IUCN had evaluated the savanna elephant alone in 2008, its optimistic status at the time may have made the species “eligible for downgrading from CITES Appendix 1” paving the way for a new, legal ivory trade, according to Georgidias. In other words, conservationists may have used the bleaker status of forest elephants as a way to keep savanna elephants from a legal trade.
But remaining on Appendix 1 did little to stave off the current ivory boom. Moreover, forest elephants continue to be worse off as a whole, yet rarely receive the same kind of attention as savanna elephants.
“The separation of forest and bush elephants will promote development of conservation strategies specific to each species,” said Hart. “Forest elephants are highly threatened and less well known than savanna elephants.”
One U.S conservation group, the Centre for Biological Diversity (CBD), is attempting to push the issue to forefront. CBD has sent a 110-page petition to the U.S. Fish and Wildlife Service making the case that forest elephants should be considered a distinct species. The group also called on the government to upgrade all of Africa’s elephants to Endangered status giving them extra protection under the U.S.’s landmark Endangered Species Act. The U.S. is commonly cited as second only to China for ivory trafficking.
“There’s now no question that African elephants are two distinct species that should be managed according to their distinct needs,” said Tara Easter, a scientist with CBD. “Both forest elephants and savannah elephants are vanishing quickly, so we must give them the stronger protections.”
This is the one thing everyone agrees on: elephants in Africa need more help.
“I think we should put the debate aside and focus instead on conserving both forest and savanna elephants, addressing the root causes of the decline in range and numbers,” said Blanc.
Yet forest elephant advocates aren’t likely to drop the question anytime soon, especially as they say the weight of both morphological and genetic data is on their side. To these researchers it is really about following the trail of evidence-based science to its destination.
“The separation of the two species should be seen as a tool to move both knowledge of the genetic history of elephants and elephant conservation forward,” said Hart.
Perhaps recognising the distinctness of forest elephants is the first step on the path to saving them.
This article was first published by The Guardian on 23 Jul 2015.