Botta’s Pocket Gopher
Thomomys bottae
Botta’s pocket gopher or valley pocket gopher are two common names for this fossorial (i.e., digging or burrowing) mammal. Botta (or bottae) honors Italian Paolo Emilio Botta, a 19th century naturalist, who visited California in 1827 on a collecting expedition for the Museum of Natural History of Paris. He is known to archaeologists as the discoverer of the Assyrian ruins of Ninevah. The generic epithet "Thomomys" comes from the Greek thomos, meaning heap, and mys or mouse. Gopher is derived from the French word gaufre, for honeycomb, a reference to the animal’s subterranean network.
Description
Rat-sized rodents with short, mostly hairless tails, minute eyes and ears, and large forelimbs with elongated claws. They weigh six to eight ounces and range in color from pale gray to russet to black, depending upon soil color. The lips close behind the large front teeth, which lets the animal dig without getting a mouthful of soil. On each side of the mouth is an external, fur-lined storage pouch.
Range
All of Arizona, southern half of Utah, most of California, western half of New Mexico, southern third of Nevada, and south into Mexico.
Predator and Prey
Strictly vegetarian, pocket gophers eat a panoply of herbaceous plants, grasses, tubers, bulbs and roots of native plants, weeds and shrubs. They generally remain in their burrows to eat and may pull an entire plant underground. At night, they may emerge to forage above ground. Water is obtained from vegatative matter.
In winter, they tunnel through the snow to feed and often stuff these tunnels with soil, creating what one ecologist calls "gopher eskers." These low anti-tunnels are common at the higher elevations of the gopher’s range.
Badgers and coyotes hunt pocket gophers by digging out their burrows, while weasels and snakes may pursue them underground. Other predators include skunks, owls (some species of which survive primarily by eating them), bobcats and hawks.
Habits and Habitat
Pocket gophers generally live where they can find good soils for excavation, which could mean any environment from the desert up into the mountains. They may be especially common in riparian areas, washes, farms and golf courses. They are active year round. One sure sign of a gopher is a mound of pushed up soil, which marks a temporary den opening.
Tunnel systems stretching for over 150 yards are not unusual. One study in Utah estimated that a single gopher moved as much as 1,130 kilograms of soil per year (a bit over 1 ton of soil). A typical one will resemble a complicated subway system with numerous forks, side branches for food storage, fecal matter and refuse repositories, and for nesting. The deepest parts of the tunnel system are between one and three yards underground. Gophers block tunnel entrances with dirt, to prevent predator entry.
They use their forelegs, elongated claws and occasionally their teeth for digging. Soil is then pushed behind and when enough loose material accumulates, the gopher turns around and shoves the dirt up to the surface. A sensitive tail facilitates rapid reversal, when necessary.
Gophers are solitary, territorial and pugnacious. The only time this changes is during breeding season, which occurs in spring. Males, which are most likely polygamous (there are generally more females in an area than males), seem to go in search of females. One to seven hairless, blind young are born 19 days later. They disperse in late summer, hoping to avoid predation. Females can mate more than once per year.
Notes
Ecologists have described roughly 150 subspecies of Botta’s pocket gopher. Subspecies designation is based mostly on geographic distribution. While all of these subspecies can interbreed successfully at this point in time, this geographic variaton is one of the first steps leading toward new speciation.
For a movie of the gopher at work click here, or on the picture below:
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