Behavioral interactions of Norway rat pups and their dams during maternal anogenital licking (AGL) were observed. Regularities in posture and orientation that may facilitate AGL were noted, and age-related changes in the pup's postural adjustments that may contribute to the decline of AGL in the 3rd postpartum week were described. It was found that cutaneous stimulation of the perineum, such as that provided by AGL, stimulates a characteristic leg extension response from pups. It was concluded that this response, which includes immobility and extension of all limbs, may permit maternal licking to continue long enough to stimulate the pup to eliminate and to allow the dam to ingest the urine. Males and females were found to exhibit similar responses and similar age-related changes. However, the latency from onset of AGL to performance of the leg extension response was shorter in males.
The behavior of young animals often differs from that of adults of the species, and may have specialized features that can best be thought of as adaptations to selective pressures that operate only during early developmental stages (Oppenheim, 198 1). The processes involved when an altricial mammal, such as a rat, locates a nipple, attaches, and sucks are prime examples of behavioral adaptations to the ecology provided by a lactating dam to her neonates (Drewett, 1983;Pedersen & Blass, 1981;Rosenblatt, 1976). A specialized behavioral pattern that facilitates maternal transport has also been described in rats (Brewster & Leon, 1980). In both of these instances, there are reciprocal adaptations in maternal behavior: The crouching of dams facilitates location of nipples, and dams grasp pups so as to elicit the transport posture.
Maternal licking is another regular feature of early life in rats. It enters the maternal repertoire during parturition (Rosenblatt & Lehrman, 1963) and is maintained at high levels into the 3rd postpartum week before beginning a gradual decline (Gubernick & Alberts, 1983;Moore & Morelli, 1979). Anogenital licking (AGL) differs both functionally and causally from maternal licking or grooming of other body regions. It serves to stimulate elimination of urine and feces from the pups and, because the dam ingests these substances, it also serves to recycle salts and fluids to the lactating dam (Friedman, Bruno, & Alberts, 1981; Gubernick & Alberts, 1983). Males receive more AGL than females (Moore & Morelli, 1979), and the stimulation pups receive during AGL also contributes toward the later development of masculine sexual behavior (Moore, 1984).