The first foray: Maternal influences in nest egression in the weanling rat

Abstract

A series of experiments was performed to examine the determinants of the rat pups' 1st excursions from the maternal nest into the novel environment outside the burrow. A standardized, nidic environment consisting of a maternal nest and adjoining open field was studied under a variety of structured test conditions. When the mother was outside the nest, pups readily ventured into the field. The early excursions were not stimulated by the mother's absence from the nest because when the mother was removed from the nest but not placed in the field the pups remained nestbound. Anesthetized dams elicited few excursions, suggesting that olfactory cues are less potent in this situation than behaviorally transmitted signals. Nonlactating adults were not attractive to pups but after induction of "maternal responsiveness" concaveated males facilitated egression. The data from a final experiment suggest that when in the nest, the dam stimulates egression by providing additional "permissive" stimuli that render the weanling more responsive to approach cues outside the nest.

Emergence of the exploratory motive in rats

“…Alberts and colleagues (Alberts & Leimbach, 1980;Gerrish & Alberts, 1997;Thiels, Alberts, & Cramer, 1990) originally proposed and investigated this idea in an elegant series of studies examining several factors in the social and physical environment that influence nest egression in infant rats. In most of these tests, infant rats were placed in a seminatural environment, which included a nest chamber adjacent to a larger chamber containing solid food and water.…”

“…These early departures from the home nest signal an important motivational shift in the life of the rat that prior to the onset of weaning has shown a strong affinity for the home nest (Leon, 1992;Thiels & Alberts, 1985). This affinity is adaptive to these altricial infants, who must depend on the mother for nutrition, thermoregulation, grooming, and protection from predators; however, the attraction to the home nest must be overcome if infant rats are to begin to forage for solid food and ultimately become self-sufficient adults (Alberts & Leimbach, 1980). Though hunger is a potential motivator for these early forays from the nest, other motivators may influence this behavior such as a drive to explore novel places (Gerrish & Alberts, 1997).…”

“…To this end, infant rats were given a choice between two identical contexts which differed only in terms of familiarity (manipulated by providing a brief preexposure to one context). We hypothesized that by removing the home nest as well as food and water sources from the testing chamber and by maintaining identical thermal and lighting conditions in each context, an exploratory motive could be more readily detected, perhaps at even younger ages than were reported in Alberts and Leimbach (1980); however, the trade-off of creating this more sensitive measure of the exploratory motive was a less naturalistic testing apparatus.…”

Warmth from skin‐to‐skin contact with mother is essential for the acquisition of filial huddling preference in preweanling rats

“…Starting approximately 2 weeks after birth, domesticated rat pups (Rattus norvegicus) can be observed to make brief excursions from the natal nest (Alberts & Leimbach, 1980;Galef, 1971;Gerrish & Alberts, 1996). At this stage, their eyes and ear canals are newly unsealed and they have recently achieved good postural control and varied gaits.…”

Huddling by rat pups: Ontogeny of individual and group behavior

“…Their behavioral repertoire expands to include playfighting and other social behaviors, but they nonetheless reliably aggregate and huddle together (Alberts & Leimbach, 1980;). …”