A comparative study of facial grooming after prey ingestion in colubrid snakes

For a comparative study of facial grooming behavior, we selected five speci es of colubrid snakes (Thamnophis sirtalis, T. butleri, T. melanogaster, St oreria dekayi, and Cyclophiops semicarinatus) based upon their phylogenetic relationships and natural diets. In an initial descriptive study, head-rub bing behavior reliably followed ingestion of earthworms in all five species . Three forms of head rubbing were identified, including two forms of labia l rubbing and one form of rostral area rubbing. The latter occurs during fo raging as well as grooming. Two additional controlled experiments were then performed. One experiment assessed the effects of multiple feedings with e ither normal or immobilized earthworms. The second tested the effects of al lowing snakes to contact surface secretions of earthworms and purified muci n without physically contacting the worm. The snakes showed a significantly greater number of head rubs when consuming active earthworms than when con suming immobilized worms, and this increased over the five trials. The snak es also head rubbed more frequently in response to earthworm mucus than to either earthworm surface wash or diluted mucin. The physical properties of earthworm mucus (adhesiveness) thus seem to stimulate head-rubbing behavior . Differences in head rubbing among the species are discussed in relation t o natural diet and phylogenetic relatedness. Furthermore, mouth gaping ofte n occurred with head rubbing and can be distinguished from yawning. Tactile and kinesthetic cues associated with this gaping behavior may aid in regul ating the occurrence of head rubbing. Neonate snakes head rubbed in a speci es-typical manner.