Squirrels And Urbanization : Short Wave Squirrels are everywhere — living in our suburban neighborhoods to our city centers to our surrounding wilderness. Rhitu Chatterjee talks with researcher Charlotte Devitz about squirrels and how studying them might help us better understand the changing urban environment.

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Who Runs The World? Squirrels!

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MADDIE SOFIA, BYLINE: You're listening to SHORT WAVE from NPR.



Hey, everyone. Let's talk about squirrels, those creatures that are almost everywhere.

CHARLOTTE DEVITZ: You know, it's a mammal that almost everybody has seen, you know, in their backyards or in their gardens, no matter where you live - whether that's in really rural areas or even in highly urbanized areas.

CHATTERJEE: Charlotte Devitz is getting her Ph.D. at the University of Minnesota. And she studies small mammals - chipmunks and squirrels.

DEVITZ: Their behavior in and of itself is really fascinating to watch. They're incredibly intelligent. They're an exciting species to work with.

CHATTERJEE: But I have to confess that I think squirrels are nothing but rodents of the trees. And I'll tell you why. You know, a few years ago, we had two squirrels that lived on the elm tree in our backyard. And for fun, my husband named them Pat (ph) and Wheatsy (ph). They were cute names for two very cute furry animals, but they were also thieves. I was trying my hand at gardening at the time, and Pat and Wheatsy were always stealing my peppers and strawberries. All the fruits of my labor went right into their bellies.

DEVITZ: (Laughter) Yeah, they certainly do enjoy stealing from people's gardens, from their bird feeders. They're incredibly smart. They can figure out how to get into pretty much everything. So we have lots of people who ask us while we're out in the field, you know, how can I get all these squirrels out of my yard? - or, you know, you could come and trap them in my backyard if you want (laughter).

CHATTERJEE: As much as some of us might want squirrels out of our yards and gardens, Charlotte says they're really useful to our understanding of urban ecosystems and how they're changing.

DEVITZ: Urbanization is kind of progressing at just an incredibly rapid rate. And so by studying a species that is actually really successful in these environments, like squirrels and chipmunks, it might let us better predict and plan for the conservation of other species as urbanization continues to progress.

CHATTERJEE: So today on the show, Charlotte tells us about her research into the world of squirrels to better understand how they adapt to their ever-changing urban environments. I'm Rhitu Chatterjee, and you're listening to SHORT WAVE from NPR.


CHATTERJEE: If you're living in North America, there are several common species of squirrels and chipmunks.

DEVITZ: Two of the kind of most ubiquitous species that you're going to see are gray squirrels and fox squirrels. But besides those two species, red squirrels and eastern chipmunks, both of which are also quite widespread in the United States.

CHATTERJEE: And these species, Charlotte says, have thrived despite the dangers of urban environments.

DEVITZ: There's the presence of the threats that people themselves might present - infrastructure changes, so habitats often get fragmented. There's, you know, vehicles now that they have to watch out for. There's novel predators, things like domestic dogs and cats. And these are all things that are kind of these new challenges.

CHATTERJEE: And so she wondered, are there aspects of squirrel behavior, their personalities, that have made them so adaptable?

DEVITZ: Some of the behavioral things that we study - when we catch the squirrels, we are measuring a number of different behavioral traits, what we call, basically, animal personality traits. And they're not this kind of anthropomorphized version of personality that we like to ascribe to our pets, per se, but more focused on things like boldness, activity levels, exploratory behavior, aggression.

CHATTERJEE: Right. So can you describe your typical day in the field when you're studying these animals?

DEVITZ: Yeah. So bright and early wake-up call - I'm usually up at about 4:30 in the morning...


DEVITZ: ...During the field season. So we - there's different methods that can be employed for trapping. But because we're working in public places, we don't leave our traps overnight. So we catch them. We then do our sample collection and behavioral tests. Everything's done in the field so that we can...


DEVITZ: ...Get the animal back to their environment, you know, as quickly as possible. So generally, we have the animals with us for 30 minutes to maybe 40 minutes maximum.

CHATTERJEE: And do you use a bait?

DEVITZ: Yes. So they have a great fondness for peanut butter. So that is our primary bait. But we're exploring some other options as well. We're playing around with different types of nuts and seeds, all sorts of things.


DEVITZ: And once they're captured, we basically tag them with little ear tags so we can identify each individual. We collect blood serum, hair, whiskers, ear tissue and a fecal sample from each animal that can be used for just a huge array of different tests that can help us just get a better picture of how they're changing in these urban environments.

CHATTERJEE: Interesting, fascinating. And you mentioned that you test the animals. What other kinds of experiments do you do with them? Just give me one or two examples.

DEVITZ: Yeah. So all of our behavioral tests occur basically in this big collapsible arena that we set up right wherever we're working. And so with, like, the open field trial, we look at how much time they're spending kind of exploring this arena versus kind of just sitting still.


DEVITZ: And we also look at what we call a dark chamber latency trial. So they're released into a dark chamber that's attached to the arena. And we basically just look at how long it takes them to kind of venture out of there and into this unfamiliar open environment. We can use that as a proxy for boldness.

CHATTERJEE: You know, I'm wondering if the pandemic has affected their behavior. I mean, I've heard there's - at least there's anecdotal evidence suggesting that city squirrels are skinnier and more skittish after more than a year of fewer people out and about and getting - with food to give them.

DEVITZ: Yeah, yeah. So it's, again, kind of one of these things where, you know, there's been benefits to us basically not being in the equation. But in some ways, it can disadvantage them. You know, if they're getting a lot of food out of trash cans on a college campus, then that food source isn't necessarily going to be there. Yeah. And you know, this isn't just something we're seeing in squirrels. But a lot of different species that are common in urban areas, there have been observed changes. One of the things that we've heard a lot from just members of the general public that we've talked to is that the populations of the squirrels and chipmunks that they see on campus or in their own backyard have increased quite a bit. So...

CHATTERJEE: Interesting.

DEVITZ: ...You know, when we're not out and about as much, you know, they might feel more confident exploring different areas or feel...


DEVITZ: ...You know, more secure to have larger litters of offspring.


CHATTERJEE: So, Charlotte, shifting gears a little bit - there's something that we haven't talked about yet. But it is important, something you've written about.


CHATTERJEE: You have Ehlers-Danlos syndrome - right? - which has affected your mobility.

DEVITZ: Yeah. EDS can have a really broad range of symptoms. It can be different for every person. But it has affected my mobility a lot because of the deterioration of my joints. So I primarily get around using a manual wheelchair. But I also will bring, like, crutches out into the field. And so, you know, have to modify things a little bit. But I was pretty much dead set on doing field research...


DEVITZ: ...And got to a point where I said - you know what? - I'm going to find a way. I'm going to figure out some system that I can work in so that I can kind of continue to pursue this even if, you know, a lot more rugged terrains may not be accessible to me.

CHATTERJEE: Yeah. So what are some of the things that you have to sort of deal with or...


CHATTERJEE: ...Things that you encounter while being in the field?

DEVITZ: Before we even start field work, you know, I go out and kind of scout the general accessibility of any site that I'm hoping to work at. I can get around really well when there's sidewalks and, you know, roads and stuff. But the more rugged the terrain gets, it gets a bit more difficult for me to get out there.


DEVITZ: And so one of the big things is that I always bring undergraduate students on to work with me. Not only is it a lot of fun and just a really rewarding experience to be able to work with, you know, budding new scientists and...


DEVITZ: ...To kind of share my love of the field, but it also is helpful for kind of getting to places that I can't. I think the most important thing has just been finding mentors, finding professors who have taught field classes that are supportive and, you know, willing to say, let's figure out how to make this work.

CHATTERJEE: So what would you like to see in terms of changes that sort of future generations of students and scientists with disabilities have more of a supportive environment and have - you know, that doing science out in the field is a little more easier for them?

DEVITZ: Yeah. Like I said, having support is super, super important for it to be successful. Having, you know, a mentor or adviser or somebody basically to help advocate and help you kind of figure out how to make things work around whatever, you know, a student with a disability has. And another big thing is providing funding for adaptive equipment. So - you know, figuring out ways to help get students equipment that would let them get out in the field, but also kind of the recognition that you can have a hundred people with the exact same diagnosis, and every single one of them could have completely different needs. And so it really comes down to communication and flexibility and being open and being kind of encouraging.


So getting back to the subjects of your research, you know, you talked about how much squirrels in the urban environment depend on us for food. My wonderful colleague Thomas has been feeding squirrels in his backyard with, may I point out, nuts bought from Trader Joe's.

DEVITZ: There we go (laughter).

CHATTERJEE: My question to you is, should he continue doing this, what I think is (laughter) an outrageous practice?

DEVITZ: (Laughter) So you know, we - this is another question that we get all the time about whether it's good to feed them or not. So, you know, they're going to get a hold of food one way or another. Once you do start feeding them, they are certainly going to return if they know that you provide a steady source of what are typically very valuable foods to them, like nuts and stuff.


DEVITZ: But by and large, it's not going to significantly disrupt their natural behavior. They're already kind of living in these environments. They're probably already stealing from everyone's gardens and bird feeders.

CHATTERJEE: Right. So bottom line - Thomas can continue giving his Trader Joe's nuts to his squirrels, right?

DEVITZ: (Laughter) For sure, yeah. I mean, once you've started, if you try and stop, they'll probably be knocking on your door asking where their breakfast is.

CHATTERJEE: There you go, Thomas. You have earned their loyalty, I guess.

DEVITZ: Exactly.

CHATTERJEE: Well, Charlotte, it was so lovely to talk to you and learn about these creatures that are everywhere in our backyards. And I have to admit, you have made me appreciate them and respect them a little bit more. Thank you very much.

DEVITZ: Yeah. No, thank you for inviting me on. This is something I'm, you know, super-passionate about, and it's something that I love to talk about.


CHATTERJEE: This episode was produced by the one and only Thomas Lu, edited by Viet Le and fact-checked by Indi Khera. The audio engineer for this episode was Josh Newell. I'm Rhitu Chatterjee. Thanks for listening to SHORT WAVE from NPR.


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