By Joseph Mooney
Nichols Arboretum is full of squirrels—and people—which makes research there particularly fulfilling for one student studying the furry four-footed creatures and how they manage in different environments.
Squirrels are everywhere—we see them in our gardens and parks and in rural areas, on the University of Michigan campus and in Nichols Arboretum. They’re cute, they run around chasing each other, bury and dig up nuts, and chatter at us from the limbs of trees. But what do we know about squirrels?
One student researcher at the U-M is looking at that question from a behavioral perspective, studying squirrels to determine how they adapt to and even thrive in our urban environments.
Charlotte Devitz is in the Frontiers Masters program in the Department of Ecology and Evolutionary Biology at U-M. She begins the second year of the program in the fall of 2019. Her master’s thesis looks at behavioral syndromes in fox squirrels along an urbanization gradient.
How Squirrels Get along with Their Environment and with People
The project’s goal, she explains, is to understand what traits help the squirrel succeed and co-exist with people. In turn, Devitz hopes, this may inform humans as they plan urban environments.
The target species in Devitz’s study is the fox squirrel (Sciurus niger). (Read more about the fox squirrel on the University of Michigan Museum of Zoology’s Animal Diversity Web.) Devitz is looking at squirrels in nine urban, suburban, and rural locations.
“We’re trying to understand what allows the species to cope with different levels of urbanization,” Devitz explains. “We focus on personality traits to see if a particular behavior is present across the study sites.” She’s also recording data on health factors, for example, observing each squirrel for wounds, parasites, mange, and other conditions.
Other studies have shown that the presence of dogs affects the behavior of wildlife. With an eye to determining any correlation between squirrel behavior and the presence of dogs, Devitz counts the number of dogs—and people—she observes. “We might see as many as 30 to 50 dogs at sites like the Arb.”
Connecting with the public is a side benefit of the project, says Devitz, and working in the Arb makes that particularly appealing. “One of my favorite parts of working in the Arb is the people walking by and the opportunity that gives me for public outreach.” And, if you’re going to be working in the field, it helps to be next to a river with a great view, she adds.
For the project, Devitz entices squirrels with bait such as nuts or peanut butter. The live trap facilitates their transfer into a special mesh and cloth bag. The bag allows Devitz to weigh the squirrel, take a tiny sample of fur from the squirrel’s tail, determine gender, and look for signs of wounds or disease. The squirrels are kept confined for only a short time before being set free where they were caught.
A Few Surprises and Points of Learning along the Way
Devitz notes that the team encountered a few surprises this summer as she conducted her research:
- Gray squirrels are calmer and nicer than fox squirrels.
- As of this article the team has seen three squirrels with bot flies. (Botflies are parasitic flies whose larvae grow in mammalian flesh or internally.)
- Devitz learned she didn’t want to do parasite research.
- Devitz has never seen a red squirrel in this area so she didn’t write them into her protocols.
- The team’s very first capture of the season was a painted turtle that was caught in the E.S George Reserve.
- Some of the traps in the U-M Diag have also enticed a few birds inside.
Field Study for Disabled Scientists
Devitz has Ehlers-Danlos syndrome, which means she must use a feeding tube and a wheelchair. In her blog “The Bendy Biologist” she writes about her disability and about the issues and challenges of navigating a difficult-to-access and in some cases inaccessible world.
A recent article in PBS News Hour talks about Devitz’s work and about accessibility in sciences and in particular field sciences.
For a look at how Devitz conducts her squirrel research see below for photographs of some of the steps in the study.
Student helpers set live traps for the squirrels.
Occasionally Devitz finds an unexpected visitor to the squirrel traps, like this white-breasted nuthatch. The birds are released immediately.
When the capture-bag test is done the squirrel is coaxed back into the cage and from there is moved to the arena, a box with different partitions and chambers in it. The squirrel is released into a darkened section of the box and the research team measures the time it takes for the squirrel to exit the darkened area into the lighted area. A side door to the box is then removed to reveal a mirror and the team notes the squirrel’s reaction to the mirror and seeing its reflection. The entire time during the arena test the squirrel is being filmed.
Devitz uses a special custom-made cloth and mesh bag, into which the squirrel is transferred after capture. After the squirrel is transferred into the cloth bag, Devitz and team time the animal’s movement with two stop watches. One runs for 60 seconds to see when the squirrel first moves in the bag after it’s secured. The second stop watch is turned on and then off whenever the squirrel moves so Devitz can time how often the squirrel moves. The mesh allows for physical inspection of the squirrel to check for obvious wounds, parasites, and to determine gender and pregnancy status. The bag helps to calm the squirrel considerably. A small sample of fur is snipped from the tail. Devitz also weighs the squirrel in the capture bag.
A squirrel in the arena looks at its reflection in a mirror.
The capture bag tapers to a point, and the pointed end has a zipper. Devitz coaxes the squirrel toward the tapered end of the bag and then partially unzips the bag. The squirrel pokes its head out the end of the bag, giving Devitz the opportunity to tag the squirrel and take a small tissue sample from the its ear.
A squirrel in the arena looks up quizzically at the camera. “The goal is to minimize squirrel stress,” says Devitz. “Their safety comes before the data.”