Lingual Luring by Mangrove Saltmarsh Snakes (Nerodia clarkii compressicauda)

—Very few cases of predatory luring by squamate reptiles involve body parts other than the tail. Here, I report the use of the tongue by Mangrove Saltmarsh Snakes (Nerodia clarkii compressicauda) to lure prey, a behavior thus far adequately described for only one other snake species. Fishes are the only verified component of the diet of these snakes and are effectively attracted by the luring behavior. Lingual luring by these snakes is particularly unique in that the tongue is curled upon itself distally such that a conspicuous loop is formed at its terminus. The rapid oscillations typical of chemosensory tongue flicks are absent, though the terminal loop does exhibit some vertical and horizontal movement. The duration of luring tongue flicks is significantly greater than the duration of chemosensory tongue flicks. Predatory luring is a means of nutrient acquisition in which one organism (the predator) produces a stimulus that is attractive to another organism (the prey) that is consumable, in whole or in part, to the predator. This often occurs in the form of aggressive mimicry (Wickler, 1968; Vane-Wright, 1976; Pasteur, 1982; Pough, 1988) or feeding mimicry (Schuett et al., 1984) in which a deceptive signal transmitted by the predator (the mimic) resembles a stimulus produced by an entity (the model) that the prey (the dupe) would normally approach. In successful predatory luring, potential prey perceive the attractive stimulus and approach the predator more closely than they might in the absence of that stimulus. This may or may not result in capture and consumption of attracted prey in a given instance, but it should do so at least occasionally (Dawkins and Krebs, 1978). Predatory luring by nonavian reptiles is widely reported and is exhibited by members of several groups therein (Neill, 1960; Drummond and Gordon, 1979; Murray et al., 1991). The most common form of predatory luring among reptiles is caudal luring, which is exhibited primarily by snakes and involves motions of the tail tip that cause it to resemble a generalized invertebrate larva suitable as prey for frogs and lizards (Pough, 1988). Predatory luring by reptiles is also achieved through the use of the tongue (i.e., lingual luring), but the taxa involved are few. The most well known example of lingual luring comes from the Alligator Snapping Turtle (Macrochelys temminckii), which possesses a bifurcate, wormlike lingual appendage that attracts fish into its mouth (Drummond and Gordon, 1979; Spindel et al., 1987). Czaplicki and Porter (1974) reported lingual ‘‘fly-casting’’ by two watersnake species (Nerodia sipedon and Nerodia rhombifer) that flicked the surface of the water with their tongues, causing fish to approach and be captured. However, because the focus of their study was not the luring, the authors’ description of the behavior is limited. Some have speculated that the straight, rigid, long-lasting tongue protrusions exhibited by vine snakes (Ahaetulla, Oxybelis, Thelotornis, and Uromacer) serve to lure prey (Lillywhite and Henderson, 1993). However, Keiser (1975) provided an effective argument against such a function for this behavior as exhibited by Oxybelis and perhaps others, at least with respect to arboreal prey, and he found crypticity a more likely role. In addition, there is no evidence to date that those tongue protrusions are attractive to prey, a key component of predatory luring (Strimple, 1992). Recently, a more detailed and convincing account of lingual luring by a snake was provided by Welsh and Lind (2000). They observed neonate and juvenile Aquatic Gartersnakes (Thamnophis atratus) quivering the tips of their tongues on the water’s surface in streams where the snakes feed upon juvenile salmonid fishes. Thamnophis atratus’ tongue protrusions during luring are of far greater duration than normal, investigative tongue flicks and are effective at attracting prey (Welsh and Lind, 2000). Herein I describe lingual luring by another semiaquatic snake, the Mangrove Saltmarsh Snake (Nerodia clarkii compressicauda). These snakes are associated rather strictly with Red Mangrove (Rhizophora mangle) around the Atlantic and Gulf coasts of the southern half of Florida as well as northern coastal Cuba (Neill, 1965; Ernst and Ernst, 2003). Fish are the only Journal of Herpetology, Vol. 42, No. 1, pp. 9–15, 2008 Copyright 2008 Society for the Study of Amphibians and Reptiles