a Pacific pocket mouse munches seeds

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A few months ago, we shared with you some major milestones in our Pacific Pocket Mouse conservation program. Mice that we bred and reintroduced into their native habitat were breeding on their own! And what's more, those new pups were starting to have pups of their own. Three generations back in the wild! Today we're back with some more news on the program to save these tiny but vital mice. These 'gardeners' of their ecoystem disperse seeds and keep the soil healthy with their burrows that increase hydration and cycle nutrients through the soil: conserving them isn't just the right thing to do—it's essential.

Leaving the mice to their own devices in the wild isn't enough to save the species, and we continue to breed them for controlled and managed release into the wild. Erin Drum, a research Associate with the San Diego Zoo Institute for Conservation Research, shares the following PUPdate on this spring's mating season.


A Pacific pocket mouse mother and her pup

A Pacific pocket mouse mother and her pup

Every February, the staff of the Pacific Pocket Mouse (PPM) Conservation Breeding Facility and some wonderful volunteers prepare our facility for the start of a new breeding season.

During the months of October through January, or the “off season,” males and females are housed in different rooms in the facility as they hunker down for a quiet couple of months, but as the mice begin to become more active, it is time to move them back together to start another breeding season. As the females and males start to become reproductive, we here at the facility start getting ready for our nocturnal lives. Since the mice are only active at night, so are we!

Even though the program has been successful in its breeding for 5 years now, and has honed its practices and techniques, breeding these mice is never an easy task.

The Pacific pocket mouse is a solitary animal, and even a receptive female can be notoriously aggressive.

Also, pairing a female in estrus with a male, does not guarantee a successful mating. Running a successful mating season is due largely to science, but a little bit of the work is an art! Choosing the pairings involves not only genetic compatibility programs, and researching past breeding notes, but also a knowledge of our captive population’s “personalities.”

As we ended March, we were excited to have our first two litters of the season! Since these little mice like to keep us on our toes, one mother gave birth a day early while the other went two days late, although both were safely in the normal range of the 22-26 day gestation period.

It’s always a very exciting way to start your shift by seeing healthy, tiny pink pups in a nest of white fluff.

Considering the facility’s success thus far, it seems we have a very busy season ahead of us!