prey, and
because it is an agile climber and able to squeeze through any openings
large enough to accommodate a woodrat, it would seem to be a formidable
enemy.

The pilot black snake (_Elaphe obsoleta_) is an important enemy of this
woodrat on the Reservation and probably throughout the rat's geographic
range except for the extreme western part. Although this snake occurs in
every habitat of the Reservation, it has been found most often along
rock outcrops of wooded hilltop edges in the type of habitat most
favored by the rat. Most often pilot black snakes have attempted to
escape into crevices of the outcrop. These snakes are also skillful
climbers and often have escaped by climbing out of reach along branches
or even vertical tree trunks. On several occasions these snakes have
been found on or beside woodrat houses, or have escaped into them. Over
a seven-year period 143 pilot black snakes have been recorded, 53 of
which were adults.

On September, 1948, a large pilot black snake found basking on a rock
ledge, distended by a recent meal, was palped and contained a subadult
female woodrat. On June 19, 1953, one of us, approaching a live-trap set
under an overhanging rock ledge, saw a four-foot pilot black snake on
top of it. The snake struck repeatedly at the rat in this trap, but was
unable to reach it. At each stroke the rat would dash about the trap
frantically.

These snakes hunt by stealth, and might catch woodrats by entering their
nests, or by lying in wait along their runways, but are not quick enough
to catch them in actual pursuit. Young in the nest would seem to be
especially susceptible to predation by the pilot black snake. These
snakes hunt by active prowling, either by night or by day, and much of
their food consists of the helpless young of birds and mammals found in
the nests. While only well-grown or adult pilot black snakes would be
able to swallow an adult woodrat, any but first-year young probably
would be able to overcome and swallow the small young. The female
woodrat's habit of dragging the young attached to her teats as she flees
from the house at any alarm must save many litters from predation by the
pilot black snake. First litters of young, born in early March, are
already well grown, and past the age of greatest susceptibility to
predation before the snakes emerge from hibernation in late April or
early May.

The timber rattlesnake is another potentially destructive enemy, but on
th