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The Camas pocket gopher (Thomomys bulbivorus), also known as the Camas rat or Willamette Valley gopher, is a rodent in the genus Thomomys of the family Geomyidae. First collected in 1829, it is endemic to the Willamette Valley in the northwest part of Oregon in the northwestern United States. It is the largest member of the genus, commonly known as smooth-toothed or western pocket gophers. The herbivorous gopher forages for vegetable and plant matter collected in large, fur-lined, external cheek pouches. Surplus food is hoarded in an extensive system of underground tunnels. The dull brown to lead-gray coat, changes color and texture over the year. The mammal's characteristically large, protuberant incisors are well adapted for use in tunnel construction, particularly in the hard clay soils of the Willamette Valley. The young are born toothless, blind, and hairless. They grow rapidly and are weaned around six weeks of age. The females have four mammary glands. The gophers make chattering sounds with their teeth. Males and females make purring or crooning sounds when together, while the young may make twittering sounds. The Camas pocket gopher is fiercely defensive when cornered, yet may become tame in captivity. While population trends are generally stable, threats to the species' survival include urbanization, habitat conversion for agricultural uses, and active attempts at eradication through trapping and poisons. In addition, it may fall prey to raptors or carnivorous mammals, or become host to a number of parasitic arthropods and worms. Scientists believe that the evolutionary history of the animal was disrupted when the cataclysmic Bretz floods washed over the Willamette Valley at the end of the last ice age. The floods nearly entirely covered the gopher's geographic range, which may have caused a genetic bottleneck as survivors repopulated the region after the waters receded.