What are Kaibab squirrels? How rare are they? How can I see one? Join this conversation with Houston Thompson, a wildlife biologist at Grand Canyon, to learn what we know about this special species, what’s still to be discovered, and what makes them so darn cute!

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TRANSCRIPT:

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Houston: You want to go out and see one? You're probably going to need to hike some miles. Maybe go for some drives, and you're just actually going to have to get lucky.

Juli: Hey there. I'm Ranger Juli, and I sat down with one of our wildlife biologists to learn more about just one of the many things that make the North Rim of Grand Canyon a special place, Kaibab squirrels.

Houston: Yeah. Hello. My name is Houston Thompson. I'm a wildlife biologist here at the Grand Canyon. Working on the North Rim in summers focusing on our Kaibab squirrels, our bison, Mexican spotted owls, and California condors, in addition to a number of other critters. Been here a couple of years and we've been making great strides, especially on some Kaibab squirrel population modeling. And that's what we're here to talk about today, I believe.

Juli: Awesome. So what are Kaibab squirrels and why is it important for you guys to be studying them here at Grand Canyon?

Houston: So yeah, good question. Kaibab squirrels are one of six subspecies of tassel eared squirrels. Tassel eared squirrels are found from here in Arizona into New Mexico, Colorado, Utah and even down into Mexico. I believe two of the subspecies are in Mexico. The largest range subspecies is the Abert squirrel. And they're what you'd be familiar with on the South Rim. They extend from the South Rim there into New Mexico, Utah and Colorado. There's another subspecies, lives the Rocky Mountain front, the Kaibab squirrel, our special squirrel here on the North Rim, endemic to the North Rim, have one and the smallest ranges of all the subspecies. So, they're very cute, cute squirrel, large white fluffy tail. And they're a fairly large squirrel as well compared to most other rodents you see around.

Juli: Can you explain what an endemic species is?

Houston: So yeah. An endemic species is a species that's just found in one geographic location, generally an isolated area. And more likely than not, they might have special traits that have allowed them to persist, and kind of evolve in place. So, it's really important for us to study these endemic species, because they can lend some of those special traits that we want to understand that helps them survive in the location they find themselves in.

Juli: For Kaibab squirrels, what are some of those traits that make them different from other Abert squirrels? And do you guys know how those traits benefit them here?

Houston: So, we know part of that answer at least. So, I mentioned there are six subspecies of this tassel eared squirrel. And they're all a little different. So mostly it's based on their pelage, which is kind of their fur coloration and patterns. So, Kaibab squirrels will have a fully white tail. That's one of the bigger differences. Whereas an Abert squirrel will have kind of a white and black, kind of black underneath. And it's a little more speckled I guess, overall. So, our Kaibab squirrels in the right light just looks like a bunch of snow or something. Their very white tail, very easy to spot on the landscape, that sort of thing. They also have, more often than not, black bellies compared to Abert squirrels that have more white bellies. Although there are actual, there have been some sightings, where that's actually reversed, but it's fairly uncommon. They believe that that change has occurred just because of one gene mutation. So Abert squirrels and Kaibab squirrels and arguably all the other subspecies used to be a little more connected through Ponderosa, and other pine forests that used to be a little more connected. And after long periods of time, some of those pine forest pockets became a little more isolated. And that's how our Kaibab squirrels have found themselves more or less stuck here on an island on the Kaibab Plateau.

Juli: So, you said that they're really easy to see because of their white, fluffy tail. But a lot of times visitors are asking, how can they see one? Where can they see one? How rare are they? How many? Do you have any answers to those questions? Any tips for how visitors might have the best chance of seeing a Kaibab squirrel, and what should they do if they see one?

Houston: Sure. So, I could go into some history of population, because it's tough. They're, they're kind of a cryptic species arguably, just because they're very quiet. They escape predators by climbing a tree and just going silent. And they're not active throughout the day. I mean, they will be, they'll bounce around, but you just kind of have to catch them at the right time. And you have to be in the right area. So, you need to be one, in pine forests, although even in our mixed conifer, you can run across them here on the North Rim. But they are pine obligates. So normally they're around, on the North Rim here, mainly ponderosa pine. Other areas they'll eat on other pine trees like pinyon, etcetera. So, part of the difficulty in seeing one now is there's just not that many, it seems. But population has always been difficult to determine. There's been biologists working on this for almost a hundred years, and population estimates vary wildly. So back in, like the 1920s, they thought maybe 5 to 10,000 of them were in existence by the 40s, maybe 3000. By around the 70s, maybe one biologist thought 1000, another thought 5 to 10,000. And even more recently, like in the late 80s, something like 22,000 squirrels was the estimate.

Juli: Wow, is that all Kaibab squirrels?

Houston: Just Kaibab squirrels. So, we've been doing some surveys that have been done historically to try to figure out how many we have. They call it a feed index. So basically, we would set up a grid, a fairly large grid, and you'd go 5 or 10 meters and count how much feed sign you found, and that'd be feed that's dropped from the tree as their feeding. It could be where they're digging up mushrooms, a number of other things as well. So, you'd count how many of those little meters had feed sign and you'd continue doing that throughout the grid. It takes a couple hours to do this, this survey. And then you'd kind of do some math to say, well, how many of those plots out of about 270 had feed, which then you could say over time is feed increasing or decreasing? And they would kind of try to extrapolate that on a landscape level to try to figure out how many squirrels we have. So not simple and I would argue pretty unreliable. So, the last decade or more, we've been doing those feed index grids, and we would just start getting zero feed sign. And we know the squirrels are around, but it's hard to extrapolate how many squirrels you have when all your grids say zero. So, we do know they've been in decline for over a decade. Maybe a fairly stark decline, having worked with the feed index grids. And we have a new kind of novel protocol here for searching for squirrels on the Grand Canyon, I might only speculate several hundred, maybe a thousand squirrels currently on the Kaibab Plateau. Again, it's kind of difficult to put a good number to it, but that's why we're working on it. So, to find the squirrel, if you want to go out and see one, you're probably going to need to hike some miles, maybe go for some drives and you're just actually going to have to get lucky. You could also go where previous people have spotted squirrels. That can be a little more reliable. Last year, for example, we had a pair in the North Rim Campground, so they were just really visible. But even then, you kind of had to get lucky. So, if you find a Kaibab squirrel, we would like to know about it. Because they're so rare currently, we take all sightings from the public and staff. We do our new survey protocol to look for feed sign. And we're building a map of where these squirrels may be. And we're then looking into why are they in the places they are? We're trying to get trends. Are they increasing? Decreasing still? Luckily, I do feel like in the last two years or so, they have been, in fact, increasing just slowly. This fall actually, some anecdotal evidence from the forest suggests maybe they’re rebounding pretty quick, which is definitely possible. They can have 2 or 3 litters a year, and each litter can have 3 to 5 squirrels in it. So, they can proliferate pretty quickly. That said, they're also pretty low on the food chain and they make a tasty snack for a wide number of predators. Historically, goshawks were considered one of their primary predators. With boom and busts of populations we don't seem to have many goshawks around right now either which allows, perhaps, for a quicker rebound. I was mentioning a feed index grid. That's been the historic method for surveying for these squirrels. Our kind of new, more novel method is really just go find the squirrels. So, we just go on hikes looking for a winter feed sign, where we document that. And then we'll actually if we find some feed trees, we will then circle around to try to map out their winter territory, which could be almost 20 acres in size. Having kind of worked through this process, we've also learned that those feed index grids are somewhat biased. You could have a historic grid just that happens to be on, say, a historic winter territory, and so maybe you're just catching sign from one territory year after year and you're not actually getting the bigger picture. And the fluctuation in sign quantity could be more of a factor of how much feed is on the landscape that year. So, maybe I should back up one more moment. These Kaibab squirrels and just tasseled squirrels in general, are the only squirrel species that's really active year-round. So, most squirrels kind of ca...

Kaibab Squirrels - Grand Canyon's Most Charismatic Mammal?

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