Effects of learned flavor avoidance on grooming behavior in rats

In Experiment 1, rats were conditioned to avoid saccharin in tapwater by pairing it with LiCl in carboxymethylcellulose (CMC) applied to the fur. Conditioned flavor avoidance (CFA) of saccharin was then assessed in drinking and grooming tests. In Experiment 2, rats were given saccharin CMC on their fur and NaCl in water (or vice-versa) as conditioned stimuli in a CFA paradigm. Two-choice tests (saccharin vs. NaCl) followed in drinking and grooming contexts. In Experiment 3, rats were given saccharin CMC on one flank and vehicle (CMC only) on the other. After grooming, animals were injected with LiCl and then given 2-choice tests, first between saccharin and water, then between saccharin-CMC and plain-CMC, and finally, between saccharin and water. Strong CFA was exhibited in drinking tests in all 3 experiments. This was not the case in grooming tests. Rats continued to groom when tastant was applied to only one flank (Experiment 1), and exhibited only weak CFA when a different tastant was applied to each flank (Experiments 2 and 3). We conclude that grooming can be directed to minimize the ingestion of noxious substances, but that such ingestion is not sufficiently reduced to affect the efficacy of grooming as a delivery method for unpalatable substances (e.g., rodenticides, chemosterilants). We speculate that grooming represents a weakness in rodents' defenses against dietary poisoning, and that it might be used to deliver toxicants as part of crop protection schemes that make use of CFA.