Behavioural displays to gustatory stimuli in newborn rabbit pups

Motor displays in the face and head regions of 33 neonate rabbits (less than 24 hrs post partum) in response to taste stimulation were examined. A droplet of taste solution was placed medially on the pup's lips and the ensuing behavioral repertoire was tallied over a 60 sec period in a double blind situation. Tastants included 2 concentrations each of sucrose, saccharin, citric acid and quinine. Distilled water was used as a stimulant and for intertrial rinses. Response characteristics to the various taste stimuli were differentiable, specific and reproducible within and across animals. Certain response features were more often associated with one stimulus than with another. Quinine often produced mouth opening (gaping) and head movements, whereas sucrose was associated with a quiet animal licking and making characteristic mouth movements. Sour reactions often resembled those to sweet, but other features helped distinguish those responses. Reactions proved to be concentration-dependent and different from those to water. Quality and hedonic value were usually accurately judged and corresponded to adult preference behaviors. It was inferred that rabbits at this early age are already equipped with a functioning taste system up to the brainstem level. Cross-species comparisons of stereotyped reactions were discussed.