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 was a loud squeal. He ran outside and paused under some limbs approximately 15 feet from the house, and remained there for 15 minutes before clipping off an ironweed 12 inches long, which he carried to the house. He did not enter the house but stopped beneath overhanging sticks at the edge, eating leaves from the plant. He made another attempt to enter the house but loud squeals and rustling followed and he returned to the ironweed plant and was still eating when observations were halted. In another instance, squeals and rustling indicated that the occupant and intruder were in combat. [Illustration: FIG. 2. Diagram illustrating spacing (due to territoriality or intolerance of the rats) in twelve woodrat houses in a hedge row extending south from south boundary of the Reservation at the middle.]