Diversity of diet influences the persistence of conditioned taste aversion in rats

Conditioned taste aversion (CTA) occurs when an animal associates the taste of a food with illness, and subsequently avoids consuming that food. CTA can be a significant obstacle to the cost-effectiveness of poison-baiting campaigns when baits contain toxicants that cause symptoms to develop before a lethal dose is ingested. In other circumstances, such as preventing rat predation on birds’ eggs, inducing CTA may be preferred to carrying out risky rodenticide treatments. Understanding the factors that influence CTA is necessary to formulate strategies for practical applications. The present study investigated whether exposure to either a diverse number of foods (varied food diet) or to one food only (single food diet) affected the strength and persistence of CTA in laboratory rats (Rattus norvegicus). Freshly weaned rats were raised on a diet of one food item or multiple food items for 17 days before being conditioned to avoid a novel food. On conditioning day, all rats ingesting a novel food (biscuits and cinnamon) were administered with a single dose of CTA-inducing thiabendazole via oral intubation. Biscuits and cinnamon were offered again to all rats once per week for 8 weeks and the consumption recorded for each rat. No rats from either group consumed the biscuits and cinnamon during the initial post-test indicating no difference in CTA strength. However, a lower proportion of rats in the single diet group consumed the novel food post-conditioning, and consumed a lesser amount of biscuits as a percentage of the total food eaten than the varied diet group indicating that the rats raised on a single food diet acquired more persistent CTA to the novel food than rats raised on the varied food diet. This suggests that the persistence of CTA and learned aversion to a particular food are likely to be greater in animals living in environments with low food diversity. Additionally, laboratory CTA studies based on animals raised on a single food should consider dietary diversity when estimating the persistence of CTA-inducing compounds.