The peeping response of pigeons (Columba livia) to isolation from conspecifics and exposure to a novel environment

The present study examined the acute behavioral responses of pigeons to separation from conspecifics and exposure to an unfamiliar environment (UE). The effects of (1) repeated exposure to the UE; (2) visual isolation from surroundings, or saline injections; and (3) diazepam treatment (i.p., 0.25, 0.75, 2.5 or 7.5 mg/kg) before the trial were also examined. UE exposure evoked intense ballistic head movements (peeping), gradually replaced with angular head movements (AHM), both associated with immobility of the trunk and legs. These behaviors failed to habituate after three trials (7-day intertrial intervals). Visual isolation from the surroundings and saline injection prior to exposure to the UE increased the AHM and reduced peeping. Doses of diazepam (0.25 and 0.75 mg/kg) that have demonstrated anti-conflict effects in other tests did not affect the behavioral responses to the UE. Diazepam at 2.5 and 7.5 mg/kg doses consistently increased time spent in immobility. These data suggest that peeping, although expressed in potentially threatening or harmful situations appears not to be a fear-motivated behavior or, alternatively, this specific behavioral response is not diazepam sensitive.