Why the cheetah's long-ago past is a problem today
Today, we’re going way back in time to look into the past of some wild cousins and see how that past is affecting them today. We’re talking about cheetahs (Acinonyx jubatus), as you must have guessed from the title. They’re the world’s fastest land mammals, but their famous speed may not be enough to help them against the threats they face today.
1896 illustration is titled “Hunting Leopard,” |
but today we’d call this cat a cheetah.
Illustration from Lloyd’s Natural History.
Wyman & Sons Limited [Public domain],
via Wikimedia Commons.
The cheetah is classified as vulnerable on the IUCN Red List, and two subspecies (the Northwest African cheetah and the Asiatic cheetah) are classified as critically endangered. Threats include loss of habitat and prey, problems with lions and hyenas (which steal cheetahs’ food and kill cheetah cubs), and persecution by farmers (because cheetahs sometimes prey on livestock). But cheetahs also have another problem, one that started a very long time ago: They are genetically pretty much the same, and that makes them vulnerable to disease and environmental changes.
The beginning of the problem
The first thing you need to know is that cheetahs, the long-legged spotted cats we associate most with the African savannah, originated in North America and began migrating into Asia around 100,000 years ago. They are more closely related to pumas than to lions or leopards. And, according to a new paper in Genome Biology, they are too closely related to each other.
According to the authors, cheetahs took a big hit in their genetic diversity when, lo those many tens of thousands of years ago, they began crossing the Beringian landbridge from North America to Asia. They then made their way through Europe and eventually to Africa. That Pleistocene epoch migration led to a “population bottleneck,” when the population shrank and individual cheetahs had huge territories (300–800 square miles) that made it difficult to get together with other cheetahs to whom they were not closely related so they could, you know, make new cheetahs.
The second bottleneck
You may be wondering why, if there used to be cheetahs in North America, there are none there today. This brings us to the second bottleneck, which happened around 10,000 to 12,000 years ago, when the continent saw an extinction event that wiped out many of its large mammals. The cheetah disappeared, as did ground sloths, mammoths, and saber-toothed cats. That left the remaining members of the cheetah species with even less genetic variation.
Why does genetic variation matter?
When all members of a species are genetically pretty much the same, one disease or environmental event could wipe them all out. The good thing about having some diversity is that, while some members of a species might succumb to a new disease, for example, others could have some quirk in their immune system that would help them survive.
Cheetahs, instead of having genetic variation, have “genome impoverishment.” The authors of the article found that “the cheetah has lost 90–99% of the genetic variation typically seen in outbred animals.” The result is that they’re vulnerable to disease and they have trouble reproducing.
That’s not good news, but here’s hoping the information from this study will help today’s cheetahs survive and thrive—and make new cheetahs.
cheetah and three cubs in |
Masaai Mara National Reserve, Kenya, 2014.
By Fabiola Leyton and Carlos Castillo
(Own work) [CC0], via Wikimedia Commons.
BioMed Central. (2015, December 8). Cheetahs migrated from North America. ScienceDaily. Retrieved December 10, 2015 from www.sciencedaily.com/releases/2015/12/151208204222.htm
“Cheetah.” Arkive.org. Retrieved December 10, 2015 from http://www.arkive.org/cheetah/acinonyx-jubatus/