Enclosure Size and Hormonal State Affect Timing of Nest Return in Female Meadow Voles (Microtus pennsylvanicus)

We investigated 2 aspects of the hormonal regulation of maternal behavior in meadow voles (Microtus pennsylvanicus): (a) when the transition in maternal responsiveness front primarily hormonal control to regulation by pup cues occurs and (b) the effect of housing enclosure size on maternal nest attendance in votes injected with a prolactin suppressant, cysteamine hydrochloride (150 mg/kg) oil Postnatal Day 2. In Experiment 1, meadow voles required 96 hr of pup contact to finish the transition from hormonal to pup-mediated maternal behavior; a period longer than found in other rodents. lit Experiment 2. females housed in larger enclosures spent less time with pups after drug injection, primarily because they increased the amount of time they stayed away front the nest each time they left. lit contrast, drug-treated females in standard cages Showed no chan,,e in their patterns of nest attendance possibly due to the presence of salient Cues from nearby pups. Under naturalistic conditions. a female vole's hormonal stale may regulate nest approach. and help establish the necessary alternation between leaving the nest (e.g., to forage) and attending pups.