Synaptomys cooperi cooperi. Cooper Lemming-vole.—In October, 1883, George B. Sudworth took one near Ann Arbor. February 13, 1903, E. H. Frothingham found one under a corn shock about four miles south of Ann Arbor. In a runway in a small tamarack stand in Steere's Swamp, near the same place, I trapped an adult female and four nearly grown young, October 8 and 9, 1903. In February, March, and April, 1921, H. B. Sherman trapped six in a field containing a little brush, a short distance south of Ann Arbor. A number of their remains were found by J. Van Tyne in the winters of 1921 and 1922 near Ann Arbor, in pellets of the long-eared owl.
Microtus pennsylvanicus pennsylvanicus. Pennsylvania Vole.—Was formerly found in beaver meadows, but with the clearing of the forests it has extended its range to the fields of grass and grain, and has become the most numerous of all the mammals of the county. Records are at hand for Ann Arbor, Pittsfield Township, and Portage Lake.
Microtus pinetorum scalopsoides. Pine Vole.—July 15, 1921, A. G. Ruthven found an adult male in the oak-hickory woods on his grounds near the outskirts of Ann Arbor.
Fiber zibethicus zibethicus. Muskrat.—In spite of persistent trapping, muskrats are still numerous in the county. Records are at hand for Ann Arbor, Pittsfield Township, Portage Lake, Saline, and Ypsilanti.
Rattus norvegicus. Norway Rat.—This injurious rodent became common soon after the settlement of the county. Its omnivorous food habits and adaptability have enabled it to increase greatly.
Mus musculus musculus. House Mouse.—The house mouse did not reach Washtenaw County until several years after the settlement of the district. It has become a serious pest, not only to household effects and stored food, but it has taken to the grassy fields and the woods bordering grain fields, and is commonly found in shocks of corn. The amount of damage done by it in this county must be very great.
Zapus hudsonius hudsonius. Jumping Mouse.—A few occur in the county. We have records for Ann Arbor, Portage Lake, and Whitmore Lake. In October, about 1880, in Lodi Township, a female jumped from a shock of corn that was pulled over, and when caught, after several jumps of two feet or more, was found to have three small young attached to her teats.
Erethizon dorsatum dorsatum. Canada Porcupine.—The first settlers found porcupines were common in the county. My father killed one in 1855 in Lodi Township, and the last one known in the county was killed near Saline in October, 1868, by John H. Bortle.
The porcupine lives on the buds and bark of several species of trees, and also eats the stems and leaves of water lilies. It is a clumsy and stupid animal, knowing under natural conditions neither fear nor haste. Its coat of sharp-barbed quills affords almost complete protection from nearly all enemies except man, who alone is responsible for its extinction in the county. Although large and clumsy, it climbs readily, and often lives in the same tree for days. It also swims quite readily, sometimes entering the water voluntarily. It makes a number of noises; it sniffs, grunts, whines, chatters, and sometimes shrieks and cries like a child.
Marmota monax refuscens. Woodchuck.—Before the settlement of the county woodchucks were not very common, a few living on the prairies as well as in the woods. With the clearing of the forests it found a congenial habitat about the fields and gardens of the settlers, and there found also choice food easily gathered. With these conditions it has greatly increased and has become a pest, so that many townships in southern Michigan pay a bounty of 25 to 50 cents each for woodchucks.