Activity trackers like Fitbits and Jawbones help fitness enthusiasts log the calories they burn, their heart rates, and even how many flights of stairs they climb in a day. Biologist Cory Williams of Northern Arizona University in Flagstaff is using similar technology to track the energy consumption of arctic ground squirrels in Alaska—insight that may reveal how the animals efficiently forage for food while avoiding being picked off by golden eagles.
This week, Williams published a study in Royal Society Open Science that compared the activity levels of male and female squirrels. He found that although males spend a lot more time outside of their burrows, they’re pretty lazy, and sometimes just bask in the sun during warmer months. Females, on the other hand, have limited time to spare when caring for their young, and use it to run around and forage for themselves and their babies. In addition to previous work on arctic ground squirrel hibernation and seasonal differences in behavior, the finding is helping his team figure out why males tend to be more susceptible to being eaten.
Williams sat down with Science to talk about creating a squirrel Fitbit, catching the animals in the wild, and how technology is improving ecological research. This interview has been edited for brevity and clarity.
Q: What got you interested in studying arctic ground squirrels?
A: It’s one of the only arctic animals that keeps a rigid schedule even when there’s no light/dark cycle for 6 weeks—meaning, they emerge from and return to their burrows the same time every day and they eat the same time each day, even though the sun stays in the sky for weeks and weeks. So I started to deploy the energy tracking technologies to better understand how the squirrels use energy through the seasons.
Q: What is it like to work with the squirrels?
A: We captured them in the wild using traps baited with carrots, and handled them from there. They’re very, very squirmy, especially the juveniles because they’re so small. The males will even bite sometimes. These squirrels are a lot feistier than other species commonly used for research.
Q: What technology did you use for the trackers?
A: The trackers were epoxied onto a collar that the animals wore. We used light loggers that were first designed to geolocate birds’ migratory patterns, but because they can detect the presence or absence of light, we use them to see if the squirrels are in their burrows or not. And the accelerometers work just like one in an iPhone. They take measurements once every second in three axes of direction, which lets us measure the index of movement. Movement is highly correlated with energy expenditure, so the accelerometers were a perfect way to measure that.
Q: Did you run into any roadblocks designing this technology?
A: There were some challenges getting the collars to be a perfect fit. When we first started, the collars were too big so the animals would shimmy them off or get limbs stuck in them. But we don’t want them to be too small that they’d grow into their skin. Just figuring how to mount a device on an animal without hurting it is always a challenge.
Q: What did you find out from the study?
A: We wanted to see just how males and females differ in their energy expenditure. Over 2 years we gathered data and saw that females have less opportunity to leave their burrows because they’re caring for their young, but when they do leave, they’re much more active than males are on the surface. Knowing how the arctic ground squirrels allot their time and energy helps us see how they avoid predators and search for food.
Q: What could be done with the technology in the future?
A: As things continue to happen at the consumer level to drive prices down, we’ll be able to use technology with more wireless capabilities. I’d like to implant a single device in an animal that can give us many measures of physiology and behavior besides energy expenditure. We could capture an animal and download data on its heart rate, metabolism, and what hormones it’s producing. This would be useful in a number of scenarios. For instance, we have a new project that will see how hormones are involved in arctic ground squirrel hibernation. And now that wireless charging is more common, we could recharge the implanted device inside the animal and send it on its way. I’m very interested to see how we can implement technology more into ecological studies.