, she was back at the
original location. On November 9, and 21, 1951, she was
again at the site 70 feet south, and was still there at her
last capture on February 3, 1952.

Ordinarily each house that is in use harbors only a single woodrat. To a
greater degree than any other kind of mammal on this area woodrats show
intraspecific intolerance. On various occasions when captives were
placed in the same or adjacent cages, they focused their attention on
each other with evident hostility, the more powerful or aggressive
individuals attacking or pursuing. Several times the confinement of two
rats in the same live-trap or cage resulted in the death of the weaker
individual, and seemingly this is the normal outcome unless the attacked
rat is able to escape. On various other occasions two or more rats have
been caught in the same trap simultaneously but in every instance these
were either: a pair of adults, the female appearing to be in oestrus; a
lactating female and one or more of her young; or young less than
half-grown, that were obviously litter mates. Older woodrats, especially
males, often have their ears torn and punctured from fighting.

Territoriality involves, primarily, defense of the house itself. An
individual that ventures into an occupied house may be quickly routed by
the occupant even though the latter is smaller. Chasing has been
observed occasionally, but it is doubtful whether any individual is able
consistently to defend the entire area over which it forages. Because
each rat spends most of its time within the shelter of its house, an
intruder might venture onto its home range unchallenged and undetected,
so long as it did not enter the nest cavity.

An adult female was live-trapped on October 14, 1951, beside her house
at the outcrop. As soon as she was released, she disappeared within the
house. After approximately two minutes, a soft, high pitched whine was
heard and immediately another woodrat dashed into view closely followed
by the female. The chase continued for several seconds in the vicinity
of the house, but the woodrat being chased soon left the area _via_ the
outcrop. Probably this intruder had moved into the house in the night
while the female was in the trap.

On June 17, 1952, an adult male was found in a live-trap set at one of
the brush pile houses in the woodland area. This house was occupied by
an adult female. He ran into the house after release, and immediately
there