One of the most satisfying experiences a conservation biologist can have is to witness the long-term effects of one’s work. Last week, Dr. Sarah Hennessy and I completed our annual surveys for the California ground squirrel translocation study, and nothing can compare to the sense of accomplishment we felt at the end of a hot, dusty day, knowing that the ground squirrels were persisting in the colonies our team created! From 2011 through 2013, we worked with our partners at SDSU to create new California ground squirrel colonies in protected reserves. Since then, we’ve returned every year to monitor the progress of our study.
You might be wondering, why study California ground squirrels? Well, I may be biased, but I find they are one of the most behaviorally interesting species in San Diego. Like many squirrel lovers, I get a kick out of their antics – new pups play-fighting with each other at the entrance of their mother’s burrow; adults stretching their front paws out, like a yoga pose, and rubbing their bellies in a dust bath to remove fleas – but one of the reasons California ground squirrels are so fascinating is that through their activities, they can change a landscape and increase biodiversity of native plants and animals! This has earned them the title of Ecosystem Engineer. Specifically, they build extensive burrow systems that are used by other rodents, lizards, snakes, and especially, burrowing owls. The owls rely on other animals to dig burrows, which they then usurp for nesting. California ground squirrels prefer open habitat, so they will cut down the grass around their burrows to use for nesting material and feed off the grass seeds. Our hope is that in time, native plants will be able to re-establish as the habitat opens up.
We’ve been going out every spring since 2011 to measure the long lasting effects of the colonies. We use various methods to measure how many squirrels are present, but we also measure the impact the squirrels have on the environment, by counting burrows and measuring the area they have cleared. This second monitoring method is what we just finished last week, with the help of a great team of San Diego Zoo Global volunteers! Due to the rains brought by El Niño this year, the grasses have really taken off, so it was hard work wading through it to find burrows. One of the grass species, aptly called “ripgut brome” Bromus diandrus has particularly sharp seeds that work their way into your socks and shoes and can be particularly painful, but one of our volunteers came up with an excellent way to protect his feet by wrapping painter’s tape around his shoes!
We want the ground squirrel colonies to thrive so that in the near future we can develop these locations into recovery sites for the burrowing owl. While we were thrilled to see proof of ground squirrels at active burrows, we are worried that the tall grasses this year will be a hindrance. Ground squirrels like open habitat because it allows them to see predators coming, and escape more quickly to their burrows. But we are hopeful, and I look forward to going out back to count ground squirrels next month!