odrats in live-traps in winter rapidly weaken unless a
large supply of food is available. If food supplies became sealed over
by ice, woodrats would have died by starvation or by falling an easy
prey to predators. The rats were more accessible to several predators
than were smaller mammals such as meadow voles which were difficult to
obtain because of the coating of ice over the fields.

The decimated population surviving into the breeding season of 1949
failed to make substantial gains. In fact, during the following
four-year period the general trend of the population over the
Reservation as a whole seemed to be one of gradual further decline.

In November, 1949, the rats were almost gone from the area of north
slope and hilltop in oak-hickory-elm woodland where the most intensive
live-trapping and other field work had been done the previous year. The
following descriptions of houses remaining on the area at that time give
some idea of the habitat, and of the course of events correlated with
the fluctuations in numbers of woodrats.

No. 1. At the hilltop outcrop, partly on a substrate of
limestone boulders, built around an elm of two-foot DBH,
which lent support to one side. A hackberry sapling one inch
in stem diameter grew through the middle of the house,
providing further support. The house was two feet high and
six feet in diameter, and was in obvious disrepair, with a
hole several inches in diameter in its top. It had been
occupied in the autumn of 1948. It was constructed mainly of
sticks, ranging in diameter from approximately one inch to
straw size. Many of the sticks, from .4 to .5 inches in
diameter and one to two feet long, seemingly would have been
heavy burdens for a rat, although they were of light-weight
wood, sumac and elm. Mixed with the sticks were quantities
of dry leaves, bark, and chips of wood, all material
appearing old and weathered. This house was in
elm-oak-hickory woods 50 feet from a cultivated field on the
hilltop to the east and south. To the north and west the
escarpment sloped away abruptly. There was a coralberry
thicket beneath the trees on the adjacent hilltop.

[Illustration]

FIGURE 1

(A) Map of part of University of Kansas Natural History Reservation,
showing first-capture sites for all woodrats live-trapped in the autumn
of 1948. Because of the short time involved and the few tr