We've been looking at giraffes all wrong for 100 years
When geneticists dug into giraffes' genomes, they found something surprising: not just one species of the long-necked animal, but four.
Courtesy of Julian Fennessy
Giraffes, with their strange long necks and distinctive fur patterns, have long puzzled scientists. When the exotic animals were paraded around ancient Rome by Julius Caesar in 46 BC, they were hailed as a cross between a camel and a leopard, a publicity stunt that later gave rise to the beasts' scientific name, camelopardalis. Nothing else quite like them roams the Earth today.
While giraffes seemed to be singular creatures, zoologists had identified separate subspecies by different fur patterns and other subtle morphological differences – like dog breeds. The scientists thought these subspecies were just varieties of the same species, Giraffa camelopardalis.
But now geneticists say they were wrong.
Four different species of giraffe were identified in a study published Thursday in the journal Current Biology.
"This changes the status of the giraffe in terms of how endangered they are," Axel Janke, a geneticist at the Senckenberg Biodiversity and Climate Research Centre and Goethe University in Germany who conducted the new research, tells the Monitor in a phone interview.
Conservation efforts, until now, have viewed all giraffes together – totaling nearly 100,000 individuals. But when considered as four separate species, they seem to be in more dire need of support. And this revelation can help shape conservation strategies, and bolster the case for funding and legislative protections.
"For a century we have thought there were nine subspecies of giraffe," zoologist Anne Innis Dagg, who was not part of the study but authored the book "Giraffe: Biology, Behaviour and Conservation," writes in an email to The Christian Science Monitor. "It is astounding to find that this is not so."
When Carl Linnaeus scientifically described giraffes in his "Systema Naturae" in 1758, he had not personally seen one, so it's not surprising that they were all initially lumped together.
Relying on previous accounts of the animals, Linnaeus was actually describing the Nubian giraffe (Giraffa camelopardalis camelopardalis), a subspecies of one of the four species identified in the new genetic study.
Subsequent research found distinctive fur patterns and coloration, and other physical traits, leading scientists to identify populations of wild giraffes as separate groups. But, otherwise the animals seemed similar enough to be categorized as subspecies.
"These differences to our eye at first glance, they're subtle," Dr. Janke says. So scientists named them as various subspecies. "And nobody questioned that until now."
Janke and his colleagues examined seven nuclear genes from the nine subspecies and found that they formed four species groupings that do not hybridize in the wild: the northern giraffe (G. camelopardalis), the reticulated giraffe (G. reticulata), the Masai giraffe (G. tippelskirchi), and the southern giraffe (G. giraffa). The Kordofan giraffe (G. c. antiquorum), West African giraffe (G. c. peralta), and Nubian giraffe (G. c. camelopardalis) are all subspecies of the northern giraffe, and the Angolan giraffe (G. g. angolensis) and South African, or cape, giraffe (G. g. giraffa) are subspecies of the southern giraffe.
"The results are fascinating but not necessarily surprising given the great difference in coat patterns," Rob Simmons, a biologist at the University of Cape Town in South Africa who was not part of the study, writes in an email to the Monitor. "The pattern fits other geographically distinct species in Africa."
The different giraffe species are about as distinct as polar bears and brown bears, Janke says. "They normally don't hybridize and have fertile offspring in nature." And, he says, the last common ancestor of all four giraffe species lived some 1.5 million to 2 million years ago, while the two bears diverged between 800,000 and 1 million years ago.
This genetic investigation began when Julian Fennessy, co-founder and co-director of the Giraffe Conservation Foundation in Namibia contacted Janke in the hopes of improving conservation techniques.
"The concern was, if you want to move giraffes or repopulate an area with fresh breeds of giraffes, can we just take any giraffe or do we have to consider the genetics as well?" Janke explains. In other words, how readily can they reproduce and maintain their population size?
When he looked at the genetic samples provided by Dr. Fennessy, Janke realized there were significant differences between groups of giraffes that conservationists would have to take into account when devising strategies to help giraffe populations remain at sustainable numbers. And further examination revealed that they were in fact different species, and therefore couldn't all reproduce with one another.
Previous conservation efforts saw all giraffes as one species, so the focus was on protecting a population of about 90,000, according to Giraffe Conservation Foundation estimates. But as the four different species don't hybridize, the numbers are much more stark than that. A population of the West African giraffe in Niger, for example, is estimated to be made up of just about 400 individuals.
That may paint a dismal picture, but it's actually good news for conservation efforts. Right now, Janke explains, "protection works on the species level. Now we know we have four distinct species, that makes it easier for conservation groups to convince African governments and other larger conservation groups to make a point that these giraffes need to be protected."
One key remaining question is what conditions drove giraffes to separate into distinct species some 2 million years ago, says Klaus-Peter Koepfli, a geneticist with the Smithsonian Conservation Biology Institute and the Theodosius Dobzhansky Center for Genome Bioinformatics at Russia's Saint Petersburg State University.
"Understanding that process is important for managing endangered populations," he says in a phone interview with the Monitor. "Whatever drove their original speciation, whether it's a geographic barrier or some sort of climate change, would also go a long way toward making sure that those processes are somewhat conserved going forward into the future."
Dr. Koepfli wasn't involved in the new study, but did work on a 2007 study of giraffes' mitochondrial DNA that also suggested particularly sharp genetic divisions among the different subspecies. This new study, he says, "is a more formal test of whether giraffe populations represent distinct species."
And discovering that there are indeed four different species of giraffe is a tantalizing hint about biodiversity more generally, he says.
"The giraffe is one of the most iconic animals in the entire animal kingdom. Realizing that what we once suspected to be one species is now four species, that really changes our view," Koepfli says. "It says that even in a large animal like this, there's still hidden biodiversity that's waiting to be discovered."