Mice like to keep themselves clean, but does this diligence extend to their homes? Video footage of a mouse gathering up objects in a shed and placing them neatly inside a box, night after night, has been interpreted as evidence for “mousekeeping”. But there could be other explanations for this curious behaviour, experts say.
The Builth Wells rodent, nicked named “Welsh Tidy Mouse” by the shed’s owner, Rodney Holbrook, was recorded gathering clothes pegs, corks, nuts and bolts and placing them in a tray on Holbrook’s workbench – a behaviour that has been going on for months. It follows a similar incident in Bristol in 2019, when a mouse was videoed “stockpiling” screws, piece of chain and other metal items inside a box of bird feed.
Assuming Welsh Tidy Mouse really is keeping its home spick and span, it wouldn’t be the only animal to engage in “cleaning” behaviour: bees and ants remove corpses from their hives and tunnels; garibaldi damselfish clear sea urchins and starfish from their nest areas and trim excess algae; songbirds carry their chicks’ droppings, uneaten food and dead nestlings away from their nests, possibly to reduce the risk of infection and alleviate smells that could alert predators.
Northern Pacific rattlesnakes also use their bodies to clear vegetation away from their strike paths in their usual stakeout spots, which may improve the accuracy of their attacks.
But whether Welsh Tidy Mouse was genuinely engaging in “mousework” or some other activity is up for debate. Although mice frequently groom themselves, and will create a separate toilet area in their cage, given enough space, said Dr Megan Jackson at the University of Bristol, who studies foraging behaviour in laboratory mice, “I wouldn’t say that this mouse has looked at its environment and thought: ‘Hey, this is messy. I need to tidy it up.’”
According to Dr Jonny Kohl, who studies the neural underpinnings of mouse behaviour at the Francis Crick Institute in London, Welsh Tidy Mouse could instead be displaying an unusual form of nesting behaviour: “It would be interesting to know whether this mouse is male or female,” he added. “Male and female mice build nests for warmth, and female mice build nests to rear their young during pregnancy. Given the low temperatures in the video, I suspect it might be the former.”
Yet it is a curious case, because some of the objects being gathered aren’t things that you would normally associate with being good for nests, said Jackson: “Usually they go for materials that provide a bit of structure and something soft to keep them warm.”
Alternatively, Welsh Tidy Mouse may be indulging its natural curiosity. Mice and other rodents often enjoy exploring new objects and interacting with them. Take pack rats, large rodents found in North and Central America: They like to hoard shiny objects such as bottle tops, keys and stolen jewellery in their nests.
Jackson’s laboratory mice, meanwhile, seem to enjoy foraging for foraging’s sake. “It is really intrinsic to a mouse to want to go out into the world, pick things up and drag them back to a place that they perceive to be a good place to store things,” Jackson said.
Whatever Welsh Tidy Mouse’s motivation, it appears to find it enjoyable. “This isn’t a behaviour that’s necessary for survival, but they are still doing it night and after night, even though they have probably learned that [Holbrook] is putting the stuff back the very next day,” said Jackson. “The fact this mouse is engaging in a pointless behaviour must mean that he finds it rewarding in some way.
“As humans we get to enjoy different aspects of life. It’s actually quite nice to see a mouse engaging in behaviour that isn’t completely necessary.”