Preference for natural odors in rat pups: Implications of a failure to replicate

The results of the present experiment indicate that very minor changes in the diet on which a rat dam is maintained can have profound effects on the attractiveness of her feces to her pups. Rat pups exhibited a strong preference for the odor of feces taken from dams maintained on one sample of Purina Rodent Laboratory Chow No. 5001, but no preference for the odor of the feces of dams maintained on a second sample of the same diet. These data point to the need for very great care in the design of experiments employing, as independent variables, stimuli which are not under direct experimenter control. The results also suggest that experience of a natural odor during ontogeny may not be sufficient for the development of a preference for that odor in young rats.