Figure 3.

Parallel effects for maternal hormones and pup experience on consolidation of maternal responsiveness and pup call recognition. Consolidation of maternal responsiveness is measured by the latency (in days) to express consistent maternal care for live pups weeks after an initial exposure to pups (or hormone treatment in the absence of pup experience). Without that exposure, or if that exposure is brief and occurs without maternal levels of hormones, the latency to express maternal behaviors on the retest is generally slow (i.e. longer than 3 days). However, in the presence of maternal hormones, an initial pup exposure as short as 30 minutes facilitates more rapid reinstatement of maternal care more than a week later. This pattern is mirrored for pup call recognition, which is measured in a two-alternative choice phonotaxis task between the playback of calls or a neutral sound. Artificially raising estradiol (E2) and progesterone (P) to maternal levels without exposure to pups is insufficient to acquire call recognition, as is brief exposure without hormones. Longer exposure without maternal hormones can be effective for establishing call recognition, but it is not maintained for the long-term, when tested a month later. The combination of maternal hormones during pup exposure appears sufficient to establish and maintain call recognition up to a month after weaning.