Voluntary and involuntary maternal separation in guinea pig pups with mothers required to forage.

Lactating guinea pigs required to leave a nest box to obtain food were observed to be separated from their pups almost 10% of the time on Days 13-15 postpartum. The duration of separation was greater in the dark than in the light, and was not different for mothers/litters exposed to low (LFD) versus high (HFD) foraging demand. Subsequently, LFD and HFD pups as well as pups reared under standard laboratory conditions (SLC) all exhibited vocalization and plasma cortisol responses to involuntary maternal separation. However, several effects of rearing were also observed. HFD pups vocalized less during separation and had higher resting cortisol levels than did SLC pups; LFD and HFD males spent less time in contact with the mother in a test cage than did SLC males. These effects are discussed in terms of the importance of the physical environment in shaping infant-mother interactions and the infant's perception of control.