Rate of Tongue Flicking by Cottonmouths (Agkistrodon piscivorus) during Prolonged Exposure to Various Food Odors, and Strike-Induced Chemosensory Searching by the Cantil (Agkistrodon bilineatus)

Abstract

Experiment I showed that cottonmouths (Agkistrodon piscivorus) explored a clean novel environment with a higher tongue flick rate than can be attributed to the effects of handling which attend transportation to the novel environment. Furthermore, exploration of the novel environment was accentuated if it contained odors derived from fish mucus but not if it contained mouse odors. Experiment II showed that high rates of tongue flicking are emitted by cantils (Agkistrodon bilineatus) after striking rodent prey. We conclude that fish odors are capable of directly activating chemosensory searching in Agkistrodon but that mouse odors only do so when they are perceived in the course of striking. Fish odors may be more salient to these snakes than mouse odors. 1979. Trans. Kansas Acad. Sci., 82:1, 1979. Burghardt (1969, 1970) has shown that chemical cues arising from potential prey activate tongue flicking and attack behavior in garter snakes. Rattlesnakes, however, do not appear to respond to chemical cues until after they have struck prey. Striking seems to be released by visual and thermal stimuli, and something about the act of striking then releases a high rate of tongue flicking and trailing behavior (Chiszar, Radcliffe and Scudder, 1977; Chiszar, Radcliffe and Smith, 1978; Scudder, Short and Chiszar, 1978). It is noteworthy that garter snakes feed extensively on worms, fish and amphibians, whereas rattlesnakes feed on lizards and mice. Perhaps the This content downloaded from 157.55.39.215 on Tue, 30 Aug 2016 06:22:43 UTC All use subject to http://about.jstor.org/terms TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCES difference in chemical cue utilization shown by these snakes is somehow related to their respective prey preferences. Direct activation of tongue flicking and other feeding responses by mucus cues (as in garter snakes) may be related to potency of such chemical stimuli and/or to the relative harmlessness of prey organisms possessing such cues. The fact that rattlesnakes must first strike rodent prey before tongue flicking is activated may be based on the subtlety of chemical cues arising from mice and/or on insensitivity to them. It is possible that chemosensation is better developed in garter snakes than in rattlesnakes and that the former are, therefore, better able to detect chemical cues arising from the environment whereas rattlesnakes may require a burst of input directly into Jacobson's organs concommitant to striking in order to become atuned to chemical cues associated with prey. These possibilities are not mutually exclusive and may act in concert to produce the differences we have observed between garter snakes and rattlesnakes. We have tried to assess these factors by a variety of procedures. For example, we have presented rattlesnakes with mucus derived from fish and have observed fairly high levels of tongue flicking even when no strike has occurred prior to chemical presentation. This never has been observed in our laboratory when mouse odors were presented, suggesting that mucus cues are indeed more potent than mouse odors. However, it is possible that mucus cues were novel stimuli to our rattlesnakes, and that high rates of tongue flicking represent facultative exploration rather than some obligate effect of chemical potency. Moreover, since rattlesnakes do not feed on fish it is difficult to interpret the significance of tongue flicking directed to such stimuli (i.e., this tongue flicking may or may not be related to feeding mechanisms). Cottonmouths feed on fish and amphibians as well as on mice. We regularly offer all of these prey types to our cottonmouths; hence, none of them should be novel to these animals. It would be interesting to see if tongue flicking can be equally activated by mucus odors and mouse odors in cottonmouths. If garter snakes evolved acute chemosensitivity because of their feeding preferences, cottonmouths would be expected to show the same trait. Furthermore, this ability might also allow cottonmouths to exhibit high tongue flick rates in the presence of mouse odors even without striking. On the other hand, if mucus cues are more potent than mouse cues, then we might expect cottonmouths to behave like garter snakes in the presence of mucus cues but like rattlesnakes in the presence of mousederived odors. The following experiments provide confirmation for the latter possibility.