By Kirsten Fenn. Produced by Rachel Levy-McLaughlin / CBC
A biologist studying abnormal stripe patterns in zebras says humans could be partly to blame for their strange look — and that it could be an early sign of problems for the species.
In a study published in the journal Molecular Ecology, Brenda Larison and other researchers looked at DNA from 140 plains zebras across Africa, including seven with abnormal stripes.
They found increased levels of inbreeding among zebra populations with unusual patterns on their coats. The researchers say it could be a consequence of habitat fragmentation.
Habitat fragmentation happens when a large habitat area is broken up into smaller areas by human-made developments like fences or roads.
According to the study, the total population of plains zebras has declined by about 25 per cent since 2002. The International Union for Conservation of Nature estimated there were about 500,000 plains zebras as of 2016.
Larison is an assistant adjunct professor in the department of ecology and evolutionary biology at the University of California, Los Angeles. She spoke with The Current‘s Matt Galloway about her research.
Here is part of their conversation.
A lot of people have an idea of what a zebra looks like. So describe what a zebra without those stripes looks like.
Well, [there are] a few different varieties.
Some people have probably seen the blond ones in the news, as we call them, which just have blond coloured stripes instead of black.
The ones that we studied have spots on the saddle or [a] kind of faded area on the saddle instead of stripes.
Another type is what we call pseudo-melanistic, because melanism causes a pure black animal. But these animals look as if the stripes kind of started growing in the middle of their torso and tried to spread outward to the extremities, but got stuck.
And so they have these odd, mottled, weird looking stripes, a lot of black on their body, and their legs and face are almost all white with just the tiniest strips of black. So they look very strange.
I think I remember a few years ago seeing … a photo of a foal that they were describing as having polka dots rather than stripes.
The bodies … look like they’re black with white stripes on the legs and then more of a polka dot body. And those ones I don’t have any samples of as yet, but those are probably the most rare ones to see.
How common is it that there would be these aberrations in the coats of zebras?
It’s fairly rare to see, but in some populations it is increasing.
If you think about Etosha National Park in Namibia, which has probably 30,000 zebras, you can go on a trip and spend a week, as I have done, going throughout the entire park and see one or two. Whereas … you could go to a park in Uganda called Lake Mburo, which has maybe about 150, 200 zebras, and see five or six of them, you know. So you’ve got maybe five per cent of the population. And there’s one in Rwanda that maybe has 10 per cent of the population with these spotted types of patterns.
What is going on here with these zebras?
We’ve been trying to figure out what genetically causes the pattern, and so our suspicion has been that it’s a recessive trait. In other words, you need to have two copies of the same version of the gene that causes it in order to see that expressed in the individual.
An individual could have one copy of [the gene] and be perfectly normally striped. But if they have two copies of that version of the gene, then they’re not normally striped.