A Western gray squirrel.
Courtesy of the Washington Department of Fish and Wildlife
Western gray squirrels are getting harder and harder to find in Washington state. They are the largest species of tree squirrels and traditionally make their homes in low to mid-elevation forests, where historically they could find plenty of oaks, pines and Douglas firs. That habitat is disappearing and changing due to timber harvests, wildfires, land conversion and climate change. Mary Linders is a wildlife biologist with the Washington Department of Fish and Wildlife. She tells us more about this large tree squirrel and what it will mean for them if Washington changes their status from “threatened” to “endangered.”
The following transcript was created by a computer and edited by a volunteer:
Dave Miller: We end today with Western gray squirrels. They are the largest species of tree squirrels. They traditionally make their homes in low to mid elevation forests where historically, they could find plenty of suitable habitat, but that habitat is disappearing, and so are the squirrels. Now, the Washington Department of Fish and Wildlife is suggesting changing their state level status from threatened to endangered. Mary Linders is a conservation biologist with the agency. She joins us now. Welcome to the show.
Mary Linders: Thanks, Dave. It’s good to be here.
Miller: You have been studying Western gray squirrels since they were initially listed as threatened in the early 1990s. Why were you drawn to them?
Linders: I actually moved to the Hood River area at that time, and there was a volunteer effort going on to map their habitat, to map the oak habitat in Klickitat County, Washington because of concern about the status of the habitat and the status of the squirrels. I wasn’t working yet, so I got involved in it that way because I’ve been doing a lot of mapping prior to that. That was this thread that led me to learn more and more about their habitat and really become entrenched, I would say, in learning about their status and trying to help in whatever way I could.
Miller: We put up a picture of a Western gray squirrel on our website that we got from your agency, and last night we got an email from someone who was very sure about their abilities to distinguish different kinds of squirrels. They wrote in part, because it was a long email, this: “I myself know these squirrels are eastern gray squirrels, not Western grays. They’re from the east coast, not native to Washington State at all. I am from the east and I have seen these all my life. Someone is wrong or seriously confused about the Washington State squirrels.” Can you help this person and all of us out? How can we distinguish between different kinds of squirrels that we might see?
Linders: That’s an excellent question, and to be completely fair, when I first moved to this area from Minnesota, I was confused as well. I always thought the squirrels back east looked totally gray until I had to go home and see that, in fact, they are brownish gray, and that is not what a Western gray squirrel looks like. A Western gray squirrel is gun metal gray. It’s about 25% larger than an Eastern gray squirrel. Its tail, as you can see from that picture, if you get a look at it, is the same volume as the body. It has very long ears and very long feet. So those are all things that distinguish it from an Eastern gray squirrel. Both species do have a whitish belly, but the Eastern gray squirrel does have a brownish wash all through the face and down the back and through the tail.
Miller: Are people in Washington, or in Oregon, likely to see Western gray squirrels digging in their gardens or just going down the street in urban areas?
Linders: Not in most places. Eastern gray squirrels have been introduced, not only to the western United States but in places throughout the world, and they’ve been very successful as an invasive species. So that is the species you’re likely to see in a lot of urban areas. There are some places where Western gray squirrels have done okay in urban areas, definitely down in California, and perhaps some of the areas in southern Oregon. You may find them in some of the cities as well, but it’s select locations, especially in Washington. It’s very rare to see them in urban areas at all.
Miller: Can you give us a sense for their lives, their lifestyles? Their nests and habits?
Linders: Yeah, they are, as you mentioned, a tree squirrel and so they use what I consider to be a transitional forest type between oak woodlands and conifer woodlands. They really like large seeded tree species like oak, like pine. Down in Southern Oregon, you actually get a whole diversity of large seeded species. Up in Washington, we’re kind of limited mostly to oak, maple, ponderosa pine, and Doug fir, [those] are most of the trees that they use up here. They use those trees not only as a source of seeds, but also for nesting. They use them for escape cover from predators. They also feed a lot on hypogeous fungi, or truffles, that are associated with the roots of these trees, but that grow underneath the ground. Their whole world really revolves around the future of these fairly large trees; small trees don’t produce the seed that they need, or the good nest locations that they need to persist.
Miller: What are the hallmarks of prime habitat? If you are walking around, what would you look out for? Let’s say you weren’t even seeing squirrels. But how would you know this was a place where they might be?
Linders: Great question. I would be looking for a relatively open understory, so not dense shrubby or lots of small trees, because those are all places where predators can hide.
Miller: I would have thought that’s where the squirrels could hide.
Linders: Well, that’s a good thought, but there’s also bobcats, coyotes, all kinds of other things that might be hiding in there. Like I said, they’re a tree squirrel, so they will move through the trees, but they will also run along the ground both in order to catch seeds and also to look for those truffles that I mentioned earlier, so they need to be able to see around them, and get to a tree for safety in their environment. As I mentioned, they also need large trees. Those trees need to be clustered so that they provide protection to the nest. If the nests are really exposed, that leaves them open to predation by owls and by forest hawks. They need those trees to produce a lot of seed. If the trees are too dense, then the seed production is the first thing a tree is gonna give up, when it’s stressed under those conditions. So we’re looking for this kind of patchy environment where there are gaps in the canopy, but also clusters of trees and an open understory.
Miller: I imagine squirrels are not crazy about a century of fire suppression in the western US.
Linders: That’s correct, and for a whole bunch of different reasons. Not only does it create a very dense forest, especially in the understory as I mentioned, but that also leaves those stands vulnerable to invasion by beetles, because they really like those kinds of small stressed stands. It’s caused a lot of issues for sure, and it of course stresses the larger trees, as I mentioned, which reduces their seed production. It also actually impacts that fungal layer as well, so you don’t get the same kind of fruiting bodies as if you’ve got some space in that forest understory.
Miller: What are the other threats currently to Western gray squirrel habitat?
Linders: Other threats actually include timber harvest, especially where that’s being implemented in a clear cut fashion. Obviously, if there’s no trees, there’s no tree squirrels. Land conversion is an issue in some areas; you mentioned fire suppression, but also the flip side of that is wildfire. Wildfire has been a huge issue for us, especially over the last decade as we see climate change really exacerbating drought conditions, and the size of fires and frequency of fires increasing.
Miller: How big of a habitat decline has this led to, and how big of a decline in actual numbers of squirrels has that led to?
Linders: Based on a habitat change analysis that we conducted recently in Washington, we are looking at more than a 20% decline in what we call Western gray squirrel primary habitat. Since listing in 1993, primary habitat is that portion of the individual squirrel’s home range that they spend the most time in. It’s where they nest, where they feed on a daily basis, especially in inclement weather. During the winter, they don’t go as far to forage. Western gray squirrels sleep in a nest every single night. Now, you can have some of those components out in the rest of their home range, but that primary habitat is really what they need. If you think about it in human terms, it’s your house and your yard. We go further than that for some of the other resources we want, but we spend the most time right there. That habitat has declined more than 20% since the species was listed, so we’re really headed in the wrong direction on that front.
As far as squirrel numbers, we don’t have a good handle on squirrel numbers. We have definitely tried to estimate that and it’s very difficult. It’s kind of a needle in a haystack problem; they’re covering a pretty large area of the state, but with very low numbers. The opportunity that we used, or the option we used instead, was to conduct occupancy surveys. We get an indication of how much of that habitat that we feel appears to provide the right resources. Do we actually have squirrels occupying? And those occupancy levels were relatively low. Now, this was just baseline data, since we’ve had to change our strategy, so we’ll conduct these surveys again in a few years and see how occupancies change, whether it’s gone up, whether it’s gone down, whether it’s stable, but it will take some time before we can actually establish a trend in the population itself.
What we did see from those surveys though that were conducted only in the very core parts of the species range is that, even in those really important areas, that the distribution is spotty and fragmented across that.
Miller: The agency is suggesting changing the state level status of these squirrels from threatened to endangered. It’s called “up-listing,” a more serious level of listing. What would it actually mean? What would it lead to?
Linders: Yeah, it’s first and foremost a heads up, both to us as an agency and to the partners we work with, that there’s more work to be done and that we need to try harder to turn the tide of where things are headed. We never want to see a species that’s already listed actually be in worse shape decades post-listing. One of the challenges of a species that’s reliant on trees is it does take a long time to actually change the habitat itself to change that trajectory and to actually regrow habitat that’s been lost. We’ll certainly be looking to work with a lot of different partners and try to increase our level of outreach, hopefully try to create some incentive programs where we can work with private landowners to do good things for the habitat on their land. Perhaps some of this kind of what we call bottom-up cutting, that might mimic fire better, so getting rid of a lot of those smaller trees that might be actually hazardous for squirrels and be suppressing the growth of larger trees. We’ll be doing a whole suite of different things and different types of outreach with state, federal, and private partners to try to turn it around.
Miller: You mentioned state and federal and private partners. My understanding is we’re only talking here currently about state level protections in Washington. They’re not listed federally, and nor are they listed in Oregon. Are Western gray squirrels in Oregon faring much better than in Washington?
Linders: I don’t want to speak for the Oregon Department of Fish and Wildlife. There is an excellent fact sheet on their website, under their ‘living with wildlife’ section. It does indicate in there that they believe squirrels are declining in Oregon and they are considered a state sensitive species in the Willamette Valley portion of Oregon. It is good that they are paying attention, they’re watching, they’re concerned, because oftentimes when we have endangerment in one part of the species range, it’s more a matter of time when that kind of bleeds into other parts of the range, right? Oftentimes it’s not that the threats aren’t there. It’s just maybe they haven’t become as bad as they are in Washington, right, so we do want to be paying attention to these things ahead of time.
Miller: I want to go back to what we talked about at the beginning: the confusion between Western gray squirrels and Eastern ones. How much of the Western gray squirrel decline is a direct result of competition with the newcomers?
Linders: We really don’t have an answer to that. We did conduct some research to look at whether the two species were interacting; that was done on Joint Base Lewis-McCord here in Western Washington, in a rural part of the base. What we found there was that the eastern gray squirrels were using more moist areas of habitat near marshes, and some riparian areas. And Western gray squirrels were more common in the upland areas. However, there was overlap between the two species and you can imagine, in an area where conditions might be different, there may be less wetland area.
Obviously, Eastern gray squirrels are all over cities, all over all kinds of things, and they do well around people, so they have a lot of supplementary food sources and are maybe a little less sensitive to that human presence than western gray squirrels are. In some landscapes, there actually may be some competition. We didn’t detect it in any major meaningful way in that particular environment. Those results were similar to a study done many years ago down in California, also in a rural area, that showed the species kind of partitioning out a little bit,. That is a common thing species do. It doesn’t pay to be in direct competition with another species if you can find ways to avoid it.
Miller: What’s it been like for you personally to witness the decline of a species that you’ve devoted, at this point, something like three decades of your career to?
Linders: Yeah, it’s really difficult. Even when I started, I mentioned that I was mapping the habitat in Klickitat County, and when I went to actually ground truth that work, there were many times where I would arrive on a site behind the loggers and the logging activities. So it was like, oh, I can’t tell whether I did a good job of mapping this because it’s gone, right? And that was really hard, all the way back then, and to see that we have been not as successful as we want to be in kind of shifting, that trajectory is difficult. Certainly watching the scale of the wildfires in the North Cascades, that should be frightening to anybody. These are stand-replacing wildfires that in an area that would have had more sporadic fire, more of a moderate intensity fire regime, or you’d have patches that burn and patches that are skipped, not just burning large stands to the ground. Once you do that and you change that fire regime, it’s really difficult to regain a suitable forest structure.
Miller: Mary Linders, thanks for joining us.
Linders: Thank you, Dave.
Miller: Mary Linders is a conservation biologist with the Washington Department of Fish and Wildlife.
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