Sometime back in May I teased a fun project I was working on by sharing a video of a strange hand reaching into a caged box. Well, I haven’t forgotten about that mysterious video, and wanted to follow up here with some concrete details about The Great Running Mouse Project. The project – more of a scientific study – has not quite wrapped up yet, so consider this teaser 2.0!
Long distance mice
Researchers have long known that captive mice run. A lot. In one study, researchers measured the amount of mileage captive mice covered on a wheel over a 6-week period, and wow were the results were impressive. The 76 mice included in the study averaged more than 7 miles a day for 42 days straight (only about 1 in 30 mice were relatively sedentary outliers). That’s the same distance I’d drive from my home in Burlington to visit my sister in Brooklyn. This 300 miles is also the equivalent of 11 marathons.
And this was all a voluntary effort (source)!! The researchers merely provided the wheel and the mice did the rest. Each mouse could dictate when they ran, how fast they ran, and how long they ran. Not surprisingly, most of their running was at night. Distance was covered in short bouts less than 3 minutes long and up to 18 minutes for longer sessions. Each bout was made up of short bursts of running punctuated with frequent rests about 30-45 second long.
Their average speeds were pedestrian by human standards, 1 to 3 mph (an average person walks at about 3 mph). But if we scaled a mouse up to human size, this would be the equivalent of running somewhere between 10 to 30 mph. Okay, so I made some big assumptions here: (1) I used a trot length for a vole, about 7 cm, from Elbroch’s Mammal Tracks & Signs, (2) I assumed a jog stride length for humans of about 70 cm, and (3) I assumed it’s fair to just scale the mouse’s speed up to match a human’s stride length. Using these assumptions, it puts the the mouse’s equivalent pace at closer to 10 to 30 mph, or between 2:00 and 6:00 minutes per mile (world record pace for the marathon was Kelvin Kiptum’s 4:34 per mile).
| As an endurance athlete, I feel comfortable anthropomorphizing the lab mice to suggest that they are demonstrating a clear love for running. Alriight, so I could be projecting here. I suppose the more depressing possibility is that, like with all of us trapped inside during the pandemic, they were just going bonkers, desperately seeking some sort of diversion from an otherwise isolating and unstimulating existence. Captive animals that live in bland, stimulus-poor environments frequently exhibit chronic stress, which can result in stereotypic behaviors (behaviors that are apparently functionless, repetitive, abnormal, and invariant).
So then the big question: Will and free mice also hop on the treadmill and run for fun (or for exercise or some other unknown reason)? This isn’t an original question. Back in 2009, Dutch neurophysiologist Johanna Meijer set up a study in her backyard to answer this very question. She put a mouse wheel inside a metal cage with holes large enough to let mice move freely in and out. She put some bait next to the wheel to lure mice into the cage, and then waited for three years, collecting over 12,000 data points. My sister tipped me off to this study and I figured hey, why not see if I could replicate this study. I just set the revised traps out with my Champlain College students and kiddos from The Wilds preschool so it will likely be another couple months before we have any real data, and so I’ll wait for our results before exploring running mice in more detail |
Refining the setup
The design for the box is pretty simple. It’s 20″x20″x30″ framed with plywood except for chicken wire on one side, which allows mice-sized animals to hop, climb, and crawl through the holes while everything squirrel sized and up are excluded (I did get video of chipmunks easily coming and going on my initial set up). I used a small mouse wheel, but when I reached out to Johanna Meijer she suggested using larger mouse wheels so we’ll see if that impacts the results.
My graduate advisor often said that good science is science that refines its questions over time. Well, good science is also science that refines its processes over time. And I settled on this design after some trial and error.
Raccoon proofing
When I ran a trial of this back in July, I quickly discovered that my boxes weren’t exactly excluding larger animals. Sure a raccoon couldn’t walk in and get the bait, but those frisky little hands were capable of reaching in. To keep them out, I widened the boxes (from 16″ wide up to 20″). I covered one side with plywood and put the bait on the plywood side, safely out of reach.
Squirrel proofing
The squirrels were also hell bent on getting the bird seed. Withing 24 hours of setting up the boxes, squirrels had dug under 2 of the 3 boxes and wreaked havoc. I tried putting chicken wire under the boxes, but it didn’t sit flat and made the wheel wobbly. I replaced this with a sheet of plywood and voila, our boxes are squirrel proofed!
And at this point, I think the set up is solid. I’ll check the cameras every month or so and keep you posted!
