Date of Award
Doctor of Philosophy (PhD)
Bennett G. Galef
It has long been assumed that animals select nutritionally adequate diets via innate and learned preferences for nutritious foods. However, animals typically fail to select a nutritionally adequate diet when a) more than two or three alternative diets are available, b) a needed nutrient is available only in a relatively unpalatable food. and c) recovery from nutrient deficiency is delayed. Because these three conditions are likely to occur in natural settings, the inability of animals to select adequate diets under such conditions suggests that our current understanding of diet selection in nature is in need of revision.
The present research indicated that failures on the part of animals to select adequate diets have been due to the artificial testing conditions used in previous diet-selection experiments. Animals in previous experiments were tested in isolation, and have therefore been denied a source of dietary information available to their wild counterparts: the diet selection behaviour of others. In the present research, rats rapidly developed preferences for a protein-rich food under the three conditions listed above when they were exposed to others feeding upon the protein-rich diet. Present data indicated that rats adopted the preferences of others by matching what other rats ate, rather than matching where others ate.
The responses of rats to the feeding behaviour of others seem well-matched to the goal of obtaining reliable and accurate dietary information from others. For example, rats were more likely to match a diet preference if several others arc displaying the same diet preference rather than if just one other exhibited that preference. Such a behaviour might serve to prevent rats from adopting an idiosyncratic, maladaptive preferences; it seems unlikely that several rats would display the same idiosyncratic maladaptive preference. Rats were also more likely to match the diet choices of large rats than small rats. Because large rats in the wild arc more likely to have acquired beneficial diet preferences than those of small rats, the tendency to preferentially match the diet choice of large rats would result in superior diet choices.
The degree to which rats match the diet choices of others while nutrient deprived and nutrient replete also suggests an adaptive interpretation. Nutrient-deprived rats matched the diet choices of others to a greater extent than did rats that were either recovering from nutrient-deprivation or completely recovered from nutrient-deprivation. The mechanism underlying the enhanced tendency of nutrient-deprived rats to match the diet choices of others did not appear to be an enhanced susceptibility to social influence. Rather, nutrient deprivation rendered rats more likely to restrict their diet choice to a single food. Thus, when nutrient-deprived rats were exposed to a demonstrator, they showed a greater tendency than non-deprived rats to restrict their feeding to the demonstrator's diet
Taken together, the results obtained in the present research indicated that social cues are a vital source of dietary information. In order to obtain a complete understanding of how rats, and, undoubtedly, other animals as well, select diets in natural settings, it is necessary to obtain a clearer understanding of the role of social influences in diet selection.
Beck, Matthew, "The role of social information in the development of preferences for nutritious foods by Long-Evans rats" (1990). Open Access Dissertations and Theses. Paper 3532.