Olfactory determinants of rat pup locomotion

Home cage odors, of which maternal droppings' odor comprises a central element, influenced locomotion in the day 15 laboratory rat even in the presence of its mother. In contrast, weanling age pups were mostly indifferent to these odors. In environments devoid of home cage odors, the day 15 pup locomoted little. However, when home cage bedding odor, or maternal fecal odor was presented to the isolated pup, or when the pup was placed on thoroughly disturbed home cage bedding, high rates of locomotion ensued. Clean bedding material elicited intermediate locomotor activity. These differences between groups exposed to various odor and bedding conditions were time-dependent -- strongest initially and decaying thereafter. Whereas initial contact with disturbed home cage bedding produced high velocity locomotion, isolation in the undisturbed home cage energized a strikingly different behavioral profile, with locomotion rare and vigorous digging predominating. These findings were interpreted under the rubric of strategies for dealing with threat given the pup's vulnerability, use of olfactory information and separation from the nest.