Summary: Fleming & Luebke (1981)

Nulliparous female rats initially actively avoid pups, whereas parturient females readily respond maternally. Nulliparous females are known to show different behavioural responses to pups, including cannibalism, covering of pups with nesting material and retrieval, although this is rare. More often, nulliparous females seem to treat pups as aversive stimuli. Fleming & Luebke (1981) tested whether nulliparous females are indeed fearful of pups, predicting that these females would show more fear-mediated responses, such as active avoidance, than parturient females. In the first study, they investigated tolerance of nulliparous females and the temporal relationship between pup-avoidance and maternal responding. They found that nulliparous females initially avoided an area with pups, but began responding maternally after 5 days, suggesting that close proximity of pups facilitates maternal responding. In the second study, they investigated that nulliparous females are, in general, more fearful to novel situations than parturient ones. They found that nulliparous females have longer emergence times, spent less time in the open and investigated less, suggesting that they show greater timidity than parturient females. Fleming & Luebke (1981) indicated that reduced emotionality in parturient females could be hormonally mediated. In the third study, they investigated whether this greater timidity was reflected in their social interactions with intruders. They found that nulliparous females were chased more often by intruders. The functional significance of heightened fear and pup avoidance is not clear, however, nulliparous females may respond more cautiously in order to minimize time and investment on young that are not their own.