Postsuckling behavioral arousal in weanling rats (Rattus norvegicus)

Twenty-day-old litters and their dams were observed in seminatural habitats consisting of a nest compartment and adjacent open field that contained powdered rat chow. It was found that pups displayed marked bursts of activity after suckling. Independent feeding reliably followed nursing bout termination (Experiment 1). Nipple withdrawal, with or without milk transfer, induced behavioral arousal whereas withdrawal of thermotactile and conspecific odor cues did not (Experiments 2-3). Increased thermogenesis was observed following milk transfer (Experiment 4). Finally, preweanling pups (10- to 12-day-olds) also displayed postsuckling arousal within the confines of the nest; full locomotor expression of this arousal was not evident until weaning age (Experiment 5). It was concluded that postsuckling arousal in weanlings functions to stimulate activities performed away from the nest and suckling, propelling pups into the field where feeding begins.