Vancouver Island's marmots survived extinction. Now, inbreeding is a concern

Humans know not to marry their cousins. But the endangered Vancouver Island marmot doesn't have much choice. One Vancouver Island researcher is now looking into the potential problem of marmot inbreeding.

A captive breeding program that helped save the rodent population may have also led to low genetic diversity

Vancouver Island marmots are considered the most endangered mammal in Canada. (Vancouver Island University/Supplied)

Humans know not to marry their cousins. But the endangered Vancouver Island marmot doesn't have much choice.

That's because researchers have been steadily rebuilding their population for more than a decade.

A captive breeding program at the Calgary Zoo has boosted their numbers from a critical low of 30 in 2003 to more than 250 today, 200 of which have been reintroduced in the wild. 

Now, Jamie Gorrell, a biology professor at Vancouver Island University, is studying a potential new problem: inbreeding between the rodents and the resulting lack of genetic diversity.

"If they all have the same gene and there was a new disease that came through the population, and they were susceptible, then all individuals would be susceptible equally," Gorrell said on CBC's On the Island.

"Once it's lost, it's lost."

Consequences of captive breeding

Gorrell said the captive breeding program has been trying to avoid the inbreeding of marmots, one of the largest members of the squirrel family. 

Researchers have built family trees and tried to estimate a marmot's parents to better dictate their mating partners.

But it's a guessing game.

A parent passes 50 per cent of their genes down to their offspring, but researchers don't know which half is shared. Two siblings might have the same genes in common, or they might not. 

Low genetic diversity is a concern because marmots — who have distinctive brown fur, beaver-like teeth and sharp claws — would be equally susceptible to a disease, which could wipe them out.

Vancouver Island marmots live in colonies either in the forest or on rocky mountaintops. (Marmot Recovery Centre)

Sharing the same DNA can also lead to inbreeding depression, which lowers the population's ability to survive and reproduce.

Gorrell will be studying the genetic diversity of both wild and captive marmots through genomic sequencing, which maps out DNA.

The results could illuminate the consequences of captive breeding in endangered species. 

Gorrell has received a 2018 Discovery Grant by the Natural Sciences and Engineering Research Council of Canada, which will grant him $24,000 per year for five years to conduct the research.

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With files from CBC's On The Island