Up All Night with Pocket Mice

Rachel holds one of her study subjects, a Pacific pocket mouse.

Rachel holds one of her study subjects, a Pacific pocket mouse.

It is summer again, which means it is time to be up all night with Pacific pocket mice! I started studying them about two years ago, when I began my PhD program at the University of California, Los Angeles (see Getting Started with Pacific Pocket Mice). Last summer, I met my first Pacific pocket mice (PPM) as I worked with Maryke Swartz and Debra Shier, trapping in the three remaining areas where the species are found to bring individuals into the captive breeding program (see Bringing in the Pacific Pocket Mouse). It was a great experience, and I learned how to look for Pacific pocket mouse burrows, the routine of setting and checking the traps (usually at midnight and 4 a.m.!), and how to handle pocket mice. I had experience working with other small mammals and rodents, but pocket mice are SO TINY; it feels really different to handle an animal that is smaller than my thumb!

This summer, I’m using all those skills and beginning my own research on how these mice interact with other rodent species in their community. Behavioral observations come with their own set of challenges. Pocket mice, like many rodents, are nocturnal. Combined with their very small size, it is almost impossible to see them! Technology helps: we get to use night vision goggles and an infrared camcorder. One thing I am studying is the mice’s caching behavior: how they store food, usually in their burrows, and specifically which other species pilfer, or steal, from these caches.

A Pacific pocket mouse (PPM) as seen through night vision goggles: she is sitting next to my backpack, and you can see how she is smaller than the buckle!

A Pacific pocket mouse (PPM) as seen through night vision goggles: she is sitting next to my backpack, and you can see how she is smaller than the buckle!

To do this, I have to get a pocket mouse to take seeds I have dyed with a non-toxic powder so I can track where these seeds end up—literally—by checking the feces of any animals I trap in the area for traces of color. I set out a seed tray by a pocket mouse burrow and sit and watch and wait for one to come out and fill its cheek pouches and take the seeds away to cache them. There have been a lot of nights where there is no activity whatsoever or when another species comes to the seed tray, and I need to make a noise or toss sand toward it to scare it off.

The nights can feel really long, but when a pocket mouse does come to the seed tray—wow! My heart feels like it stops for a second when I first spot it and when I am frantically (silently and motionlessly) determining whether it really is a Pacific pocket mouse. The next 20 or so minutes are thrilling as I get to watch it make multiple trips from the seed tray to its burrow. Often times they are quite furtive at first, taking long pauses in the shrub cover, spending only a few seconds at the tray before disappearing again. After a couple of trips, they seem to become a little less hesitant and spend up to a minute at the seed tray, filling their cheek pouches and running directly back to their burrow. After taking all the seeds from the tray, one little female decided to investigate us! She took a few minutes to approach us as we sat in chairs and watched silently. She came up to where my backpack was sitting on the ground right next to me and even touched my shoe. Moments like this make all the waiting worth it, and it is such a privilege to see these tiny, fascinating animals in action!

If you are interested in learning more about the research I am doing, you can check out this short video I made!

Rachel Chock is a doctoral student at the University of California, Los Angeles, and is working with Debra Shier, Ph.D., from the San Diego Zoo Institute for Conservation Research.

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