Table 1.

Intruder Challenge Behavioral Ethogram

Behavior	Description
Aggression	Focal subject gives/receives aggression to/from the intruder/cagemates. Contact (e.g., bites, slaps) and non-contact (eg, threats, lunges) are counted.
Latency to approach intruder	Time from the start of test until the focal subject first enters proximity (1m) to the intruder.
Approach intruder	Number of times the focal subject enters proximity (1m) to the intruder.
Activity	Focal subject moves across the substrate (eg, walking, running, swinging across cage, etc.).
Environmental exploration	Focal subject engages in active manual, oral, or pedal examination, exploration, or manipulation of the environment.
Social contact	Focal subject is within arm’s reach of the cagemates.
Behavioral withdrawal	Focal subject remains motionless, and does not engage in social interaction, activity, or environmental exploration.
Stereotypy	Focal subject engages in repetitive, nonadaptive, rhythmic movement (e.g., pacing, flipping, saluting).
Threat vocalizations	Focal subject emits aggressive barks.

Note. Behaviors were scored as duration (seconds), with the exception of threat vocalizations, aggression, and approach intruder, which were scored as frequencies.