“Varmints” in the Garden!

By Tamara Blett

Do gophers and other burrowing critters in your garden make you want to play “whack a mole”? If so, you’re not alone, the digging rodents are known to create havoc in landscapes; eating plant bulbs, roots, fruit and vegetation, and turning yards into surfaces resembling swiss cheese, as they tunnel their way through your yard and through our lovely planting areas here at the SLO Botanical Gardens. The burrowing rodents in the Central Coast are most commonly either California ground squirrels or pocket gophers. Both are common in residential settings and here at the SLO Botanical Gardens, so let’s take a closer look at these critters and see what they are all about.

pocket gopher -Thomomys bottae.jpg

Pocket gophers are named for their cheek pouches, used in transporting food to their burrows.  Gophers are fossorial, meaning that they eat, sleep and breed underground, and are rarely seen aboveground. They are usually brown with tiny ears, long whiskers, and a short, thick, almost hairless tail. Gophers are herbivores who mostly eat the underground parts of plants (roots and tubers) but occasionally surface for a bite (or more!) of greenery, sometimes pulling whole plants back into their burrows, for a later snack. The presence of gophers can be identified in the garden by large mounds of soil next to an exit tunnel.

CA ground squirrel.jpg

The California ground squirrel is found throughout the state and thrives where winters are mild. Ground squirrels are a mottled grey and brown on top, with a lighter color on their bellies, a white eye ring, and bushy tails.  They are easy to identify because they forage above ground but will retreat to their burrows when frightened (distinct from tree squirrels, who instead climb a tree when startled, and never use burrows). Signs that grounds squirrels are at work nearby include many adjacent holes, smooth little paths in and around the tunnels, or loose plant material from vegetation feeding.

Do gophers and ground squirrels carry diseases? Well, as with many other animals such as wood rats, prairie dogs, chipmunks, mice and rabbits, gophers and ground squirrels can be infested with plague carrying fleas. This is relatively rare for gophers, but occasionally possible for ground squirrels because they live in large colonies, where diseases can be transmitted quickly. Burrowing rodents can also spread other diseases, so caution (and gloves) should be used when near animal burrows, and unusual number of dead rodents should be reported to public health officials.

Here at the Botanical Gardens, we discourage gophers and other burrowing animals in our planting areas by encouraging natural predators such as owls and hawks. The SLOBG has installed many owl houses and hawk nesting platforms around the perimeter of the gardens to provide free lodging for any birds willing to stand guard duty and enjoy free meals. These sharp-eyed raptors are even better at rodent control than humans could be, because they are on duty 24/7 and have keen sight and hearing designed just for locating prey. As a last resort, if the animal burrows become too dense, or enter vulnerable planting beds in the gardens, we use “smoke bombs” (administered by trained applicators) for below ground treatment of the critters.

For dealing with burrowing animals at home, we recommend that you: (1) Identify which type of critters are present; (2) Locate “fresh” areas of activity, by flattening out soils mounds with a shovel, and only treating the area if new mounds appear (also cover up old, inactive holes) and;  (3) Visit your local nursery or ranch supply store to ask what pest control products and deterrents work in your area. The options will be in one of two categories: non-lethal (discourage the critters from visiting specific garden areas) or lethal.  Non-lethal options may include planting new perennials and shrubs with “root baskets” surrounding the below-ground portions of the plant; broadcasting castor oil pellets or liquid spray (a natural repellent) around active burrows and throughout planting areas; or ultrasonic sound deterrents (sometimes effective for small areas). Lethal options may be desired for large acreages, or severe, recurrent damage to property or landscapes. These include setting traps or using smoke bombs or poisons, and all should be used with caution or under the guidance of a licensed professional.  

If you can’t beat them…. then try to appreciate the burrowing mammals for their place in the environment. Gophers and ground squirrels help add nutrients to soils; decomposition of the plant material underground, along with rodent poop can produce deep fertilization of soils. The burrows and furrows made by the tunnels provide soil aeration which can capture rainfall that might otherwise runoff and be lost. And gophers also serve as food for our owls and hawks… nature’s natural “varmint” control.