I was hard at work on the moth guide this morning (three weeks to our deadline!) when Dan called up to me that there was an unusual mouse in the pool. Drowned, unfortunately; though we’re out at the pool two or three times a day, often, rodents that fall in overnight usually swim themselves to exhaustion. It’s a problem we’ve struggled to deal with; Dan put a board in the water today and we’ll see if that helps, but I think the best way to prevent critters from falling into the pool is to have an above-ground pool, or not have one at all. I assume they come to the pool looking for water to drink, but why do they fall in? Do they accidentally stumble over the edge in the darkness of night, not realizing the drop? It’s a bit of a mystery.
I grabbed my camera, despite the poor creature’s condition, because this wasn’t just any mouse: it was a Meadow Jumping Mouse, Zapus hudsonius, and it was a species I’d never seen before either alive or dead. When Dan described it to me he said it had a tail twice as long as its body, and really long back legs, which are the jumping mouse’s two distinctive characteristics. The hind legs, of course, are used to help it leap long distances, while the extra-long tail is used in balancing during these manoeuvres.
The only mammal guide I own is actually a section of the Reader’s Digest North American Wildlife, a hardcover book that I remember consulting growing up, and still find a useful reference for tidbits of information, or as a mammal or plant guide. Their image of the jumping mouse lacks the white underside or the buffy streak down the flank clearly visible on this individual, but there’s no mistaking that tail. Or those legs. And look at those long toes! They would also be an adaptation for stability in jumping.
The book indicates that the mouse “can leap across distances of 5 feet or more.” I’m not sure where they took their info from, but Wikipedia disputes that number, suggesting that 2-3 feet is more the norm (apparently at the start of the 1900s it was claimed they could jump as much as 8 to 10 feet in one bound! For a creature whose nose-to-tail-base is only a couple of inches this would be quite a feat. Studies in the 1930s actually observed the mice and came to the more modest values). What everyone does agree on is that the leaping is primarily an evasive manoeuvre, and the mouse usually moves in steps of only an inch or two when foraging, perhaps up to a few to several inches at a time when traveling.
Despite the name, Meadow Jumping Mice do occur in both meadow and forested habitats, though they typically prefer the open spaces. They are true hibernators, digging a burrow where they sleep away the winter in a low metabolic state. At more northern latitudes they may spend up to seven months of the year in hibernation. They mate immediately after emerging in the spring, and give birth to naked, blind young a mere 18 days later. A month after that the youngsters are independent and out on their own – it’s a turnaround that rivals many songbirds in its rapidity, and allows them to bear two litters in a summer.
Wikipedia notes that jumping mice are decent swimmers, and will often retreat to water when trying to escape danger. Could that be the reason this poor fellow ended up in the pool?