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Today on Animal Fact Files we’re discussing jumping mice– specifically the North American species in the genus Zapus. These rodents range across most of the continent, from southern Alaska to the southern U.S. spanning from coast to coast. Fewer than 10 living species exist in this genus, and they prefer meadows over forests—although they’ll enter damp wooded areas if there’s no competition. They avoid dry environments and can even swim short distances, but with their limited stamina they tire quickly, so it’s a risky maneuver.

Jumping mice get their common name from their escape tactic: jumping! Although not as springy as their woodland relatives (Napaeozapus), they can leap about 3 feet, 1 meter, in a single bound. When fleeing, they zigzag to disorient predators such as owls, foxes, skunks, weasels, snakes, and even large fish—yes, fish! Since they swim, they occasionally cross paths with hungry aquatic hunters.

A jumping mouse’s oversized back feet and longer hind legs help power its jumps and distinguish the group from common house mice. Jumping mice rarely enter human homes and are actually considered beneficial to have around! These rodents eat weed seeds and pest insects along with berries and fungi. They spend their active months mating and procreating before fattening up for a long hibernation underground.

Emerging in spring—males first, then females— jumping mice are quick to find mates.Their nests are globular and hidden in dense vegetation or under logs. After a ~3-week gestation, 5–8 pups are born blind, deaf, and helpless. Amazingly, it takes only 90 days for them to reach adult size, and early-season females may even breed that same year! Depending on location, they have 1 to 3 litters annually with those in the warmest parts of the range producing more than those in the colder regions.

Once autumn arrives, these rodents spend just a few weeks eating enough to gain upwards of 50% of their body weight. On average, jumping mice weigh about 20 grams, but they can gain 6 grams or more during this bulking period. Once fat enough, they'll head into a self dug burrow and enter a low activity state. During this 6 to 8 month long hibernation, the mouse’s heart rate drops to just a few beats per minute and its body temperature is barely above freezing. Only about 1 in 3 survive, but those that do can live up to 3 years in the wild!

North American jumping mice are usually darker across their back and lighter along their belly and have two-toned tails: dark above, white below. They average about 8 inches, 20 centimeters long, and that's including their tail, which is longer than their body. Their large feet have five toes, and they have small eyes mid-way between their nose and ears. When first born, jumping mice have white teeth, but these fade to orange over time.

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