Spontaneous mouse killing rats: gentling and food deprivation result in killing behavior almost identical to that of rats with medial hypothalamic lesions.

Rats that were found to kill a mouse spontaneously were divided into two groups. One group was left untreated and allowed free access to food while the other was gentled for 15 min/day and given only 15 g of food/day. Nonkilling rats were induced to kill mice by lesions of the medial hypothalamus. Seven to ten days after being divided into groups or subjected to brain lesions, each rat's behavior toward a series of stimuli was observed. The stimuli were a live mouse, a second live mouse, a freshly killed mouse, and a cotton wad. Food-deprived/gentled spontaneous killers and rats induced to kill by medial hypothalamic lesions each tended to attack with higher intensities and lower latencies than control spontaneous killers. The food-deprived/gentled spontaneous killers and lesion-induced killers (but not the control spontaneous killers) also attacked a dead prey moved vertically and then held onto the prey with sufficient intensity that their feet would leave the floor of the cage before they would release their grip on the prey. It is argued that the behavior of food-deprived spontaneous killers may constitute a more valid model of spontaneous mouse killing than that of sated spontaneous killers. The close correspondence between behavior toward a prey by lesion-induced killers and food-deprived spontaneous killers suggests that the lesion-induced killers fit this model of mouse killing remarkably well.