By Audrey F. Baker
Talk about intriguing animals! Botta’s pocket gopher (Thomomys bottae) qualifies. A true recluse, spending 90 percent of its life in its subterranean domain, the secretive creature is the original “Miner 49er,” and a master of architecture.
For “Bottas” fans, sighting opportunities are limited to a rare feeding session at burrow’s edge, while pushing dirt out of a burrow, or when on the move to new quarters.
Meanwhile, Bottas are busy doing what they do best — digging!
Five species of pocket gophers are found in California. Ours, Botta’s pocket gopher is the most widespread. The species name derives from the fur-lined, external cheek pouches (pockets) that extend from the side of the mouth well back onto the shoulders. They are used to carrying food and nesting materials to its den.
As well-equipped miners, Bottas are capable of burrowing into diverse soil types — loose sands, hard-packed clays, semi-arid desert soils. Their adaptability is enhanced because, unlike their claw-digging counterparts who are restricted to softer soils, they use both their large well-enameled teeth and their claws to dig.
A tunneling lifestyle also requires powerful forequarters. Short fur that doesn’t mat in wet soils, small eyes and ears, and highly sensitive facial whiskers assist in moving about in the dark. A hairy tail is useful to feel around tunnels when walking backwards. Even the lips are a specialized tool. They close behind four large incisor teeth to keep dirt out of the mouth while digging. Front feet and head operate as a bulldozer.
Bottas have a “git-r-done” attitude. In a year, one pocket gopher can move 1 to 2 ¼ tons of soil.
All this is accomplished by a creature 7–10.5 inches long, including a 2–2.5-inch tail. Males are larger than females. Weighing in at 5.6–8.8 ounces, they continue to grow throughout their lifetime. The ladies, 4.2–7.1 ounces, stop growing after the first pregnancy.
Mining demands intensify with increased soil density. Compared to moving across a surface, it requires 360-3,400 times more energy. A low basal metabolic rate and thermal conductance (heat obtained from the materials around them) allow Bottas to conserve energy.
Except for breeding season, each burrow is inhabited by a single adult. In a world not affected by day and night light cycles, Botta’s pocket gophers put in a nine-hour work day. While they don’t whistle while they work, they do communicate by making clicking noises, soft hisses, and squeaks.
The king of the underworld exhibits true architectural genius. Multiple deep chambers (up to six feet below ground) serve as burrow nesting, food storage and defecation sites. Near-surface tunnels (6–12 inches below ground) are used for feeding on plant roots. Side tunnels are disposals for excavated soil.
At surface level, Bottas create fan-shaped mounds of excavated soil marking the general location of its burrow. The holes are 2.5 to 3.5 inches in diameter. A male’s burrows can cover 5,000 square feet; female’s extends to 3,000. Most range from 200 to 2,000 square feet. The real entrance is filled in with a plug of soil for protection. They aggressively defend a larger surrounding area.
Botta’s gophers enjoy a number of habitats — woodlands, chaparral, scrubland, and agricultural lands. They are only restricted by densely rocky terrain, barren deserts, and major rivers where the soil is too soaked to accommodate their required oxygen levels.
As herbivores, gophers prefer herbaceous plants, shrubs, and trees. A sensitive nose locates roots and fleshy plant parts found while digging. From below, they pull entire plants into their tunnels. Shoots, grasses, roots, tubers are favorite munchies. Above-ground feeding is accomplished no more than a body length from their “feed-hole” tunnel. The object is to eat, and not to be eaten. Hungry critters abound in the above-ground world.
Tirelessly mixing and aerating soil, Botta’s pocket gophers are nature’s dynamos, moving deep soil layers to the surface, making minerals available to plants and increasing soil fertility.
Their efforts bring plant diversity and reduce erosion. Gophers also assist with the housing shortage. Abandoned holes soon house toads, salamanders, snakes, and more, and serve as avenues for predator avoidance. A very intriguing animal!
— Audrey F. Baker is a trail guide at Mission Trails Regional Parl. For more information about the park, visit mtrp.org. Call 619-668-3281 for more information on the park’s free offerings and opportunities to learn more about natural Southern California. Special walks can be arranged for scouts, clubs, or other organizations of any fitness or mobility level. Contact Ranger Chris Axtmann at 619-668-3277 or [email protected].
