High-end habitat: improving the habitat for the Pacific pocket mouse

Matt Lucero

When most people hear Laguna Beach, images of sand, surf, and palm trees flash through their minds. While it may be known for its high-end homes, and amazing beaches, Laguna offers much more. Within its hills lie riches of a very different kind; priceless works of nature only found on the coast of southern California. I am talking about the Pacific pocket mouse (Perognathus longimembris pacificus; PPM), and the habitat that it relies upon. This tiny animal, ironically, has made its home on some of the most desired land in California: the hills, and cliffs overlooking the Pacific Ocean. Endemic to the coast of southern California, and northern Baja California, Mexico, the PPM live in the endangered plant community called coastal sage scrub.

Over the past year, our small mammal team has successfully released 49 captive bred PPM into a 1.6 hectare fenced area. The fence serves the purpose of allowing the PPM to become familiar with their new surroundings, while deterring terrestrial predators from entering the area. Although the heavy rains over the past winter were desperately needed, with them brought an unforeseen obstacle: a boom in all native, and non-native plants within the enclosure. Our team was literally waist deep in plants that usually only grow a foot high. With this amount of overgrowth, the PPM habitat virtually disappeared. Not only did this make monitoring extremely difficult, it made this new habitat unsuitable for PPM. Like most animals, PPM have strict habitat needs, but this includes more than just the plants. The soil itself plays a huge part in their survival; PPM require open ground with sandy patches to dig burrows, and sand bathe. Sandbathing is a behavior that allows them to clean themselves, as well as mark their territory with their scent. When our team picked this release site, it met all the requirements, but none of us could have predicted the extreme spring growth.

This is where working with endangered species is about management. Most think it is all about increasing the number of animals; while this is crucial, without the proper habitat, the animal in question will not survive. Our team was faced with the challenge of clearing native and non-native plants from an already fragile environment. Pulling weeds… how hard could it be? We have all done it one time or another, either as a chore for our parents, or in a garden of some sort. When we first thought of the task ahead, we figured a day or two, and it would all be done. How wrong we were. Because this area is on a preserve, our only method is to pull by hand, or with small shovels. We wished we could have used mowers, and large machinery, but due to the fragile landscape this was not an option. Not only did we have to be cautious of PPM burrows, we had to make sure we were removing mainly non-native plants, and leaving native plants that could be used by the PPM for shelter and as a food source. After hand pulling for one day, filling a pick-up truck, and only making a small path, we quickly realized this was going to be much more than just pulling a few weeds.  

Enter the San Diego Zoo’s volunteer forces: a group dedicated to assisting us in any way possible. Without their help, we would not have been successful. Along with volunteers, our team hand pulled over 2,000 pounds of vegetation. Aside from pulling, we also needed to haul away all the pulled vegetation. This became months of work by itself, but luckily we were able to rent a very large dumpster. A dumpster large enough to drive a truck into, that at first our team thought was overkill, but after two days it was filled to the top. And we filled it to the top twice! With the volunteers help, the PPM habitat is back in working order. Not only did we clear the ground which created new areas for the animals to inhabit and spread, we were able to shape the future for this critically endangered species. So now when you visit Laguna Beach, remember there is much more than meets the eye.

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