Finding could alter conservation strategies for long-necked animals.
One of the most iconic animals in Africa has a secret. A genetic analysis suggests that the giraffe is not one species, but 4 separate ones — a finding that could alter how conservationists protect these animals.
Researchers previously split giraffes into several subspecies on the basis of their coat patterns and where they lived. Closer inspection of their genes, however, reveals that giraffes should actually be divided into four distinct lineages that don’t interbreed in the wild, researchers report on 8 September in Current Biology1. Previous genetic studies2 have suggested that there were discrete giraffe populations that rarely intermingled, but this is the first to detect species-level differences, says Axel Janke, a geneticist at Goethe University in Frankfurt, Germany, and the study’s senior author.
“It was an amazing finding,” he says. He notes that giraffes are highly mobile, wide-ranging animals that would have many chances to interbreed in the wild if they were so inclined: “The million-dollar question is what kept them apart in the past.” Janke speculates that rivers or other physical barriers kept populations separate long enough for new species to arise.
Ruminating on ruminants
The study tracked the distribution of 7 specific genetic sequences — chosen to enable researchers to measure genetic diversity — in nuclear DNA from skin biopsies of 190 giraffes. They also looked at the animals’ mitochondrial DNA. The sequences fell into four distinct patterns that strongly suggested separate species. Janke says that each of the four species is about as different from each other as the brown bear (Ursus arctos) is from the polar bear (Ursus maritimus).
The researchers suggest replacing the current species name, Giraffa camelopardalis, with four new ones: the southern giraffe (G. giraffa), found mainly in South Africa, Namibia and Botswana; the Masai giraffe (G. tippelskirchi) of Tanzania, Kenya and Zambia; the reticulated giraffe (G. reticulata) found mainly in Kenya, Somalia and southern Ethiopia; and the northern giraffe (G. camelopardalis), found in scattered groups in the central and eastern parts of the continent. The one remaining subspecies is the Nubian giraffe (G. camelopardalis camelopardalis) of Ethiopia and South Sudan. It is a distinct subspecies of the northern giraffe.
“This study is pretty persuasive,” says George Amato, a conservation biologist at the American Museum of Natural History in New York City, who has conducted extensive research on the genetics of African wildlife. “I applaud the science and what it adds to our understanding of African biogeography.”
Janke says that the findings have obvious implications for conservation: all of the giraffe species must be protected, with special attention paid to the northern and reticulated giraffe. Each of those species has fewer than 10,000 individuals. According to the Giraffe Conservation Foundation, the overall number of giraffes has dropped from more than 140,000 in the late 1990s to fewer than 80,000 today, largely because of habitat loss and hunting.
But applying the new findings to conservation efforts may be difficult. “So far, we haven’t really been able to fully appreciate the power of genomics in conservation,” says Aaron Shafer, a geneticist at Trent University in Peterborough, Canada. Genetics can uncover new species, but it's not always obvious how that knowledge should guide decisions about animal protection.
Amato notes strong parallels between giraffes and African elephants, which were classified as a single species until a 2010 study3 provided genetic evidence that there were actually two: forest elephants (Loxodonta cyclotis) and savannah elephants (Loxodonta africana). That finding increased calls for extra protection of the forest elephant, the rarer of the two.
However, assessments of African elephants by the International Union for Conservation of Nature treat the animals as one species, due to concerns that splitting them into two species would place forest and savannah elephant hybrids into a kind of conservation limbo.
Evidence showing that many populations of American bison (Bison bison) carry small amounts of domestic-cattle DNA4 prompted concerns over whether it was worth saving the contaminated herds, since they weren't completely wild. Amato and other biologists have argued that the animals still deserve protection. “They are ecologically functional bison,” Amato says.
It remains to be seen whether the latest study will have any impact on giraffe conservation, he says. The most immediate effects may be felt in zoos that trade the mammals for breeding purposes: now that researchers have identified separate species, it should be easier for zookeepers to make appropriate matches.
The discovery of separate giraffe species could have come sooner, but the animals have been largely neglected by science. “Giraffes were fairly ubiquitous in their habitat, and they weren’t much of a target for poachers,” Amato says. “They are an iconic animal, but they were taken for granted.”
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Woolston, C. DNA reveals that giraffes are four species — not one. Nature 537, 290–291 (2016). https://doi.org/10.1038/nature.2016.20567