BIOLOGY AND HABITAT USE OF THE MAZAMA POCKET GOPHER (THOMOMYS MAZAMA)IN THE PUGET-SOUND AREA, WASHINGTON

The ecology and distribution of the Mazama pecker gopher is poorly und erstood and several subspecies are being considered for state and fede ral protection. We studied Mazama pocket gophers near Olympia, Washing ton from February-April 1992 and in April 1995 to describe their biolo gy and habitat use as part of a larger assessment of experimental popu lation control methods. Males were significantly larger than females i n mass and standard body measurements. Gophers from two sites, Lacey a nd Olympia, Washington, had similar physical measurements, although go phers near Lacey weighed more and had longer tail and hind foot length s, while gophers near Olympia had longer ear lengths. Olympia males ha d longer baculum lengths. The capture of pregnant and lactating female s and dual occupancy of some burrows by males and females indicated th at breeding activities were underway during this period. There was a n early 1:1 sex ratio of males to females. Densities were lower (10/ha) near Lacey in an orchard with mowed grass and forb understory and past population control than for an unexploited population at the Olympia site (60/ha), containing a Christmas tree plantation with an understor y of orchard grass and the invasive, introduced Scotch broom. Food cac hes occurred about 53 cm in depth and held about 200-250 g of root cut tings (2,500 g maximum), indicating that gophers in the area fed heavi ly on thistle and Scotch broom. Pocket gophers reinvaded 22 of 25 (88% ) burrow systems within 10 weeks after removal trapping. The conflicti ng goals of population control to reduce agricultural damage versus pr otection of rare or threatened pocket gopher subspecies requires bette r information on taxonomy, distribution, and population status of subs pecies. Limited home range sizes (108 m(2) for males; 97 m(2) for fema les), dependence upon common herbaceous and woody foods, and rapid rei nvasion rates suggest that rare subspecies may be readily managed if t axonomic and population issues are clarified.