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Home , Gopher, Ground squirrel, Prairie dog, Utah prairie dog

TRACKING Burrowing & Ground © Tim Gunther

terry shistar, PhD 8 pounds. They are known for sitting upright as they look for danger. Ground squirrels of all sorts live communally in ophers and ground squirrels are an important underground. Most ground squirrels are mainly her- part of the in which they live, although bivorous, consuming roots, seeds, fruits, buds, and foliage. they are viewed as a nuisance because of the un- They also eat fungi, some Gderground burrows, tunnels, and mounds that they , and some have create for their . Gophers and ground squirrels have been observed eating oth- some similarities, but the biggest difference is that ground er small and squirrels live in colonies, while gophers are usually solitary. eggs. The herbivorous diet Key to the role they play in supporting the ecosystem in which and burrowing behavior they live is the fact that both gophers and ground squirrels have earned these animals share their burrows with other animals. the label of “pests.” © iStockphoto/bahadir-yeniceri Gophers are called “pocket gophers” because of the Gophers and ground external fur-lined cheek pouches, extending to their shoulders, squirrels use their burrows in which they carry food and nesting materials. Gophers are to seek safety from preda- rarely seen above ground, and their systems may cov- tors and shelter from bad er an area of 200 to 2,000 square feet, with shallow tunnels weather, hibernate, sleep, for feeding, and deeper tunnels for food storage and nesting. raise young, and defecate. Gophers do not hibernate. They are nocturnal The burrow has separate chambers devoted to different uses. who eat roots from their underground tunnels and foliage However, the burrows serve other functions as well. They help grabbed from around a hole. to aerate the soil, capture snowmelt and rainfall that would Gophers push earth to the surface as they dig burrows. otherwise run off and cause , and fertilize the soil. The mounds thus formed may be distinguished from molehills They help in seedling establishment of the seeds that the by their shape—in the form of a crescent or horseshoe, as rodents harvest and store, and in distributing mycorrhizal opposed to the ’s volcano-shaped mound. The shallow fungi. Even more importantly, the burrows are home to tunnels of moles tend to create a ridge of soil on the surface, many other animals, some of whom are predators of rodents. while tunnels are deeper and do not show up on Furthermore, these rodents and their burrows form the the surface. basis of large . Many other animals, including Ground squirrels range in size from , who some endangered , depend on the burrows of gophers weigh a few ounces, to dogs weighing 1–3 pounds, to and ground squirrels. The following describes the importance (also known as woodchucks), averaging around of ground squirrels in California:

22 Pesticides and You • winter 2019–20202019 www.BeyondPesticides.org “Belowground, the burrows are sheltered and cool no way that is not duplic- matter the weather above. This comfortable climate draws ated by other species.”2 a diverse cast of animals—mice, , tarantulas, A number of the inhabit- and several species of beetles that live exclusively in ants of rodent burrows tunnels. Then there are the local amphibians. Ground squir- are threatened or endan- rels actually make it possible for moisture-loving amphibians gered species, including to live in the hot, dry hills of the Diablo Range. As the weather black-footed ferret, © iStockphoto/fishysam warms and ponds dry up, California red-legged frogs, western California red-legged toads, ensatina salamanders, and California tiger salamanders frog, California tiger retreat to the cool refuge of burrows—often while the salamander, Northern squirrels are still living inside. The frogs and toads come and Idaho , go, but the taxicab-tinted tiger salamanders move in for the and . long haul: they stay underground for up to ten months each year, emerging only in winter to breed. With this crowd, squirrel Box 1 burrows are almost mini-ecosystems of their own. Worms Managing Land with Burrowing Rodents and beetles crawling out of the walls may get eaten by the amphibians, while mice and voles go after the squirrels’ caches of nuts and seeds. Larger creatures—burrowing owls, , ith an understanding of the ecosystem benefits of and San Joaquin kit foxes—often enlarge abandoned burrows ground burrowing rodents, the goal of landscapers and convert them into dens. But ground squirrels do even Wseeking to protect the playability of a sports field or the more for grassland ecosystems than spread seeds and build mowability and aesthetic impact on a grass yard or flower and shelters. Plentiful and prolific, they are a dinnertime mainstay vegetable garden is to create a deterrent for these animals to for most of California’s savanna predators. Local badger settle in the middle of your property. If you are in a position to let populations depend almost entirely on ground squirrel colo- nature take its course, the ecosystem will find an equilibrium with nies, says retired district naturalist Ron Russo. And studies natural predators reducing the population. Owls like to eat rodents of golden eagles in the park district show that ground squir- and, over time, act as effective managers of rodents. rels may comprise up to 70 percent of their diets when the birds are rearing their young. DiDonato says the sheer abun- However, with the pressure to maintain a field or a garden, dance of ground around San Antonio Reservoir and Sunol the key to a successful program that respects burrowing rodents’ Regional Wilderness supports the densest population of role in the ecosystem, while discouraging them from choosing nesting golden eagles anywhere in the world. And back your site, is to reduce the ’s food source and shelter, en- when grizzly bears prowled California, they dug out entire couraging them to find another place to inhabit. Small mesh colonies for a snack.”1 heavy gauge wire fencing, with two feet buried in the ground Similarly, prairie dogs appear to be a , and three feet aboveground can exclude prairie dogs. Trenches since other organisms in the are so dependent may serve as barriers to other burrowing rodents. Plants that are on them: cited as repelling gophers and ground squirrels include gopher “Interestingly enough, the survival of many other species purge (Euphorbia lathyrus), castor bean (Ricinus communis), and seems to hinge on the survival of the prairie dog. About 90% garlic. In extreme cases, unwanted burrowing animals can be of the [black footed] ferret’s diet consists of prairie dogs. In effectively managed in both agricultural and residential settings addition, the , ferruginous , and through use of traps, barriers, natural , and other diets include a large percentage of prairie dogs. According physical methods. Predators include gopher , corn to Nicole Rosmarino/Southern Plains Land Trust, the mountain snakes, rat snakes, owls, , great blue herons, , 3 plover appears to be a prairie dog obligate or, at the very bobcats, coyotes, and domestic dogs and . least, is highly dependent on prairie dogs for survival, using the borrows for breeding, nesting, and feeding. Burrowing Understanding the role that organisms play in the broader owls, prairie falcons, badgers and a host of other prairie ecosystems provides the basis for seeking to avoid the use animals are associated with prairie dog colonies. In fact, of poisons that have indiscriminate effects among numerous some ecologists consider the prairie dog to be a keystone organisms and creates an imbalance that escalates pest prob- species of the prairie. According to Miller et al., nearly 170 lems. In the case of gophers and ground squirrels, finding a species rely on prairie dog colonies to some extent for their way to tolerate these rodents by separating them from suscep- very survival. Miller further concludes that the prairie dog tible plantings will help conserve other species that depend fits the definition of a keystone species because prairie dogs on them and their burrows. affect the ecosystem structure, function, and composition in a

1 Lord of the Burrows: The Incredible Edible Ground Squirrel, http://baynature.org/articles/jan-mar-2008/lord-of-the-burrows. 2 http://environmentalchemistry.com/yogi/environmental/200706prairiedogreconciliation.html. 3 Pesticide Research Institute, 2014. Technical Evaluation Report for Exhaust Gas. https://www.ams.usda.gov/sites/default/files/media/Carbon%20Monoxide%20TR.pdf.

www.BeyondPesticides.org winter 2019–2020 • Pesticides and You 23