JACKSON APPARENT EFFECT OF WINTER INACTIVITY 
63 
having been shot on the ice were given. The minimum distance between 
the mainland and the nearer islands is approximately 1^ miles, which 
would by no means be excessive even for some of the smaller mammals. 
Into the second category (B), those mammals which are active in 
winter and frequently found among logs and driftwood near the beach, 
fall the Canadian white-footed mouse, red-backed mouse, meadow 
mouse, masked shrew, and short-tailed shrew. These mammals were 
probably carried to the islands on driftwood, particularly with the ice 
floes and jams- in the spring. The power of these floes to carry debris 
and vegetation can be appreciated only by one who has seen the results 
of the impacts of this ice along the shores of the islands. 
Turning now to the mammals of the mainland as represented by 
observations made at Bayfield, and collections and observations made 
at Herbster and Orienta, Wisconsin, we find present all of the species 
of mammals found on the islands and in addition the following rela- 
tively common: gray chipmunk (Tamias striatus griseus), little striped 
chipmunk (Eutamias borealis neglectus), striped ground-squirrel (Citellus 
tridecemlineatus tridecemlineatus) , Canada woodchuck {Marmota monax 
canadensis) j jumping mouse {Zapus hudsonius hudsonius), porcupine 
{Erethizon dorsatum), Mearns cottontail rabbit {Sylvilagus floridanus 
mearnsi), Minnesota skunk {Mephitis jnephitis minnesotoe), and the 
black bear {Ursus americanus americanus). A glance at this list and 
we note that with the exception of the cottontail all of these mammals 
are inactive in winter. The cottontail has only recently ingressed the 
region, having made its first appearance near Bayfield within the last 
ten years. The same applies to the striped ground-squirrel. Of the 
other mammals not found on the islands the gray chipmunk, little 
striped chipmunk, Canada woodchuck, jumping mouse, and black 
bear are known to hibernate; the skunk, while not in a true state of 
hibernation, remains in a state of lethargy during the winter in a den 
in the ground; and the porcupine at this season is inactive, spending 
weeks at a time in the top of a single tree or in a hollow log in the forest. 
The hibernating mammals spend their dormant periods in nests in the 
ground and are well protected from the effects of ice erosion which 
takes place in the early spring. The point of course can be raised that 
only negative evidence is supplied as proof of the absence of these 
mammals on the islands. But this negative evidence is so strong that 
it is fairly conclusive. Special effort with approved means of collecting 
was made to obtain each of these species on the islands. Methods of 
calling chipmunks, ground squirrels, and woodchucke v/hich never 
