Immobility reactions in socially behaving rabbits: Relation to hippocampal electrical activity

The presence of an intruder conspecific of the same sex caused a series of conflict reactions in rabbits living in a semi-natural environment. In some animals, defensive responses were predominant and two immobility reactions were observed. One consisted of freezing when the intruder was exploring at a distance; the other consisted of subdued posture in close contact with the intruder. Hippocampal EEG, recorded by telemetry, showed two different profiles. During freezing, rhythmic slow activity prevailed and during subdued posture an irregular pattern was predominant. Frequency increased when the intruder was in close contact with the resident. Aspects such as distance or behaviour of the intruder were found to affect both behavioural strategies and hippocampal electrical responses.