A recent UC Davis report found inbreeding in the dwindling populations of red foxes in California’s Sierra Nevada and Lassen regions.
These red foxes are smaller than other fox species and are equipped with fuzzy paws and thick coats. It’s an adaptation that allows them to survive in their cold, montane habitat.
They declined in number after unregulated fur trapping that began in the late 1800s. Although the practice is now illegal, researchers say inbreeding is a likely reason why they’ve since failed to recover and are now critically endangered. In the Lassen Peak region, estimates say there are only around 30 individuals left.
But the new report offers a possible solution: Genetic rescue. It’s a conservation strategy where outside populations of an animal are introduced to one that’s been impacted by inbreeding in order to boost genetic diversity.
Cate Quinn, a U.S. Forest Service research biologist and a lead author of the study, spoke with CapRadio about why this solution could work and how it might help researchers learn more about using this method on other species.
This interview has been edited for clarity and length.
Interview highlights
What did California red fox populations look like historically?
One of the problems with conservation of the Sierra Nevada red fox subspecies is that for a long time, it's been hampered by lack of information. We have a very poor historical baseline. We don't really know what we would be trying to restore to.
If we were to go back 100 or 150 years ago, according to early naturalists, the native endemic red foxes would have been predominantly found in the major mountain ranges. There's a few notable exceptions but … since then we've really muddied the waters by moving foxes all around. We've introduced them to new areas.
One of the things that we could do with this study is we could use a molecular approach. By sequencing whole genomes of individuals, we could use that to actually peer back in time before there were so few individuals and say, “what would this have looked like hundreds or thousands of years ago?” And try to reconstruct that history.
In this Dec. 13, 2014 file photo provided by the National Park Service from a motion-sensitive camera, a Sierra Nevada red fox walks in Yosemite National Park, Calif.National Park Service via AP, File
What do these populations look like today?
If we were to zero in on the Sierra Nevada subspecies, there's two populations. There's one in the Sierra Nevada and one in the vicinity of Lassen National Park in Northern California. Both of those are very small in numbers of individuals.
They have low genetic diversity and they're completely isolated from each other. And so, generally, those characteristics are not a great suite when we're thinking about long-term viability and conservation.
The report highlights inbreeding as a potential root issue for the decline of these red foxes. How does that impact a population?
When populations get really small, individuals have no choice but to mate with related individuals. And through that process of inbreeding, what happens is that harmful genetic mutations that were once very rare in the population rise in frequency and then become common. You can think of genetic disorders like reduced sperm quality, heart defects, abnormal skeletal deformities, things like that.
So all of those issues can accumulate and then affect the ability of red foxes to survive and reproduce.
Inbreeding depression [is] such a distinct threat because it can occur long after the original threat is passed. If it is the case that inbreeding depression is limiting their population growth, that needs to be addressed explicitly and sort of separate from any environmental threats because it could continue for decades or generations after the original threat has been mitigated.
Then there’s the strategy proposed in your research to answer this problem. Can you tell me about genetic rescue?
Genetic rescue is when managers take animals from a different but related population and they move them into the inbred population. Then the offspring of those individuals — it's called outbreeding — reverses the inbreeding.
Infusing the inbred population with more variation masks the effects of these harmful mutations. The offspring — and then ideally the offspring of those offspring — have higher fitness, and that releases the population to grow and expand.
Where has genetic rescue worked?
The most well-known is the Florida panther, and that happened in the 90s.
There's a discussion in our field in general, the field of conservation genetics, of should this be used more often? And is it underused because of fear of doing harm?
It's more of a theoretical tool than it is a realized tool. So it's talked about in the literature, but it has not been implemented very many times.
What do you hope managers can take from this study?
What my hope would be, whatever happens, is that we maximize the learning potential for all of this. If genetic rescue happens in Lassen, there's potentially a lot we could learn that then we could apply to other species in similar conditions.
And so thinking about it in terms of, not even success or failure, but how can we extract as much information from this to do conservation better and in other species.
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