Earth Notes: Mouse Footprints

Aug 14, 2019

It’s not easy to spot the New Mexico jumping mouse, a golden-furred critter that lives along streams in the Southwest. It’s rare, quick, and secretive. To find the animal, scientists have built a new kind of mousetrap—one that doesn’t hurt the mice at all, but tricks them into leaving inky footprints behind.  

New Mexico jumping mouse
Credit Jennifer Frey

Jumping mice hibernate for three-quarters of the year, but get plenty of exercise in summer when they fatten up, find mates, and raise young. They can climb, swim, and leap huge distances propelled by their enormous back feet—researchers describe them as acrobats and ninjas.

Those unusual feet inspired biologists at Northern Arizona University to create a trap called a “track plate.” It’s a clear plastic shoebox with an inkpad inside. Steel-cut oats and peanuts lure the mice in. After snacking, they exit the box and leave behind telltale footprints on a sticky sheet of paper.

Researchers tested the track plates in the forests of eastern Arizona and western New Mexico. The extra-long toes of the jumping mouse were easily told apart from the tracks left by other rodents. In fact, a track plate works just as well as a traditional live trap for discovering where the jumping mouse is hiding—and it’s a lot less stressful.  

That’s important, because the New Mexico jumping mouse is endangered. Its favorite habitats along streambanks and rivers have been overgrazed by cattle, leaving them without the tall flowering plants they need for food and shelter.

The more scientists learn about this ninja mouse, the better the chance of keeping it from vanishing entirely.