Nature Notes

Volume X No. 3 - August, 1937

Mammals On Wizard Island
By R. R. Huestis, Ranger Naturalist

Mammals of Wizard Island

ground squirrel

Three of four species of diurnal mammals have been reported as living on Wizard Island in Crater Lake. The mammals are, the brown coney, Ochotona princeps brunnescens Howell; the golden-mantled ground squirrel, Callospermophilus chrysodeirus chrysodeirus (Merriam); and a chipmunk. The latter might be Allen's Chipmunk, Eutamias townsendii senex (Allen), or the smaller Eutamias amoenus amoenus (Allen), the Klamath Chipmunk. Both species of chipmunks may have been seen.

On July 28, 1937, twenty delusion (live) mouse traps were set along the trail leading to the top of Wizard Island. The traps were set among lava rocks and under logs. These traps took two adult female Mazama red-backed mice, Clethrionomys californicus mazama (Merriam). These mice are relatively rare specimens in trap-lines and very little is known about their life history. It is an interesting fact that the type specimen of this subspecies was taken by C. Hart Merriam and Vernon Bailey on the south side of Crater Lake, August 15, 1896. The two trapped specimens closely resemble in color and measurements the specimens described by Bailey.* The measurements tabulated below are in millimeters.

Total LengthTail Vertebrae FootEar
162.851.5 19.011.2
157.253.7 18.412.0

It may be seen from the above that the two specimens of Mazama red-backed mice have tails about one-half the length of the body and small ears. They also have small eyes. They are bright reddish brown along the back with greyer flanks and a pale cream-colored ventral surface.

On August 8 twenty delusion mouse traps and twenty large and small snap traps were set on the north slope of Wizard Island. The delusion traps took four deer mice, Peromyscus maniculatus ssp., and the snap traps took one Peromyscus, some coneys and golden-mantled ground squirrels. Only one Peromyscus was an adult. It measured 172.3 x 81.8 x 22.3 x 18.4. These measurements are duplicated by specimens taken along the rim; in color the specimen presented no obvious differences from the mainland type. No chipmunks were taken at this time nor in a previous night's trapping, and none have been seen on the island this year (1937).

The mammalian fauna of Wizard Island is interesting because no one knows how the animals got there. Coneys are common inside the rim of Crater Lake but they never venture any distance from the home rock slide. Swimming Skell Channel, the narrowest arm of water between the island and the mainland, would be quite out of character for them. It seems improbable that they would venture out of their winter retreats and cross the island on ice. Golden-mantled ground squirrels are in hibernation in the winter. It seems quite improbable that they would swim across although this method of transportation may be possible. Peromyscus swim readily. They could easily have been transported by a boat, a method of travel which would also be open to squirrels and chipmunks. The habits of red-backed mice are insufficiently know to venture comment on how they got to Wizard Island.

While visiting the island during the summer months Dr. R. M. Bond found signs indicating the presence of either a fox or a bobcat. It seems quite possible that a more extended investigation might show, in addition to deer mice, Mazama red-backed mice, ground squirrels, and coneys, the presence of which has already been determined, or past occupancy, of still other mammals of Wizard Island.

*Bailey, Vernon, The Mammals and Life Zones of Oregon, N. Amer. Fauna No. 55, U.S.D.A. Bur. of Biol. Sur., June 1936.

Wizard Island

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