Snake prey odors

A square field (80 x 80 cm), with a milk-glass floor, marked off in 5 cm squares, opaque walls and a clear Plexiglas top was used. Snakes were placed in an open-ended cylinder and placed in the middle of the apparatus and the snake was allowed 1 minute to adapt. The cylinder was lifted and the snake was allowed to explore the apparatus for one minute during which tongue-flicks were videotaped. No prey or prey odor was ever placed in this apparatus. 

Odors can have delayed and unexpected effects. Garter snakes, T. sirtalis, were presented with either live earthworm or mosquito fish, Gambusia affinis, in a screen-covered bowl for several days. One day after transferring the snakes individually to a box free of prey odors, they were tested with aqueous extracts of fish and worms on cotton swabs. Snakes exposed to fish odor attacked fish extract less, and those exposed to worm attacked worm odor less. This is interpreted as habituation with a possible switch to other prey. This also demonstrates that in any experiment with chemical cues an odor not experienced for 22 hours may still have an effect (Burghardt, 1992). 

Timber rattlesnakes, Crotalus horridus, are ambush hunters. They assume the ambush posture after smelling prey odors. In the laboratory, these snakes recoil the front part of their body into the ambush posture after flicking their tongues... 

On land, snakes prey on salamanders and their eggs. The ringneck snake Diadophis punctata) and its prey, the salamanders Plethodon richmondi and Plethodon dorsalis provide an example. Salamanders were given a choice between a paper towel that had had a ringneck snake on it for 48 hours, and one with clean water. The salamanders of both species avoided the substrate with the odor of the ringneck snake (Cupp, 1988). 

FIGURE 12.4 Skatole, a prey odor used by snakes. 

Twenty-two cells, one from each snake, were monitored for activation by prey stimuli. All cells responded to at least one stimulus. We report here the results on nine of these neurons. These cells were systematically tested with different concentrations of stimulating substances and with appropriate control stimuli. In all cases, air delivery of prey odors activated MOB mitral cells but not AOB mitral/tufled cells. Conversely, liquid delivery of prey odors activated AOB mitral/tufred cells, but not MOB mitral cells. Control substances, pure air and snake Ringer s solution, failed to activate any cells (Figures 5-10). 

Halpem M., Halpem J., Erichsen E. and Borghjid S. (1997). The role of nasal chemical senses in garter snake response to airborne odor cues from prey. J Comp Psychol 111, 251-260. 

Traversing a maze in which no proximate odor cues are present, but in which snakes have previously received rewards was here defined as a foraging task. Such a task permits one to analyze tongue-flick patterns before and after prey consumption. 

Two phenomena of reptilian prey searching are well investigated responses of various snakes to the odors of invertebrates, and rattlesnakes trailing of envenomated small mammals. 

The rattlesnake C. viridis searches for the particular odor it had experienced when striking the prey. In one experiment, snakes were induced to strike perfume-treated mice. Then they were exposed to perfumed, but non-envenomated, carcasses. The snakes preferred a carcass with the same odor as the originally struck mouse. In a second experiment, snakes preferred the carcasses of mice on the same diet as the ones they had struck. Thus rattlesnakes form a... 

Snakes can learn to discriminate profitable from less-manageable prey. Naive garter snakes, Thamnophis melanogaster, attacked both the carrion-eating leech Erpobdellapunctata and the blood-sucking leech Haementeria officinalis even though naive snakes respond less to the odor of H. officinalis. The latter thwarted... 

In their predator avoidance, salamanders use complex odors that combine chemicals from both predator and prey. In the laboratory, red-backed salamanders, P. cinereus, avoid filter papers soaked with water extracts from garter snakes that had been preying on salamanders, while earthworm-fed snakes lacked this effect. Exudations from unfed snakes and extracts from homogenized salamanders had no such alarming effect (Madison etal, 2002). 

Blind snakes find their prey by using the prey s pheromones. The wormlike Texas blind snake, Leptotyphlops dulcis, of the southwestern United States leads a subterranean life and feeds on termites and ant brood. It finds ants by following their pheromone trails (Gehlbach etal, 1968). Other blind snakes such as the American blindsnake, Typhlops pusillus (Gehlbach et al, 1971), and the Australian blindsnake, Ramphotyphlops nigrescens (Webb and Shine, 1992), also follow odor trails of ants, their prey. Texas blind snakes are attracted to the simple alkaloid skatole (methyl indole Fig. 12.4), an amine with an unpleasant odor from the ant Neivamyrmex sp. (Watkins etal, 1969). 

Olfactory and vomeronasal bipolar neurons may differ in their responsiveness to stimulating substances and these differences in response characteristics could provide important clues to their differential functions. In garter snakes a spectrum of chemical stimuli (standard odorants, amino acids and prey products, including purified proteins from earthworms, a favored prey of garter snakes) applied to the vomeronasal epithelium modify unit responses in the AOB (Inouchi et al., 1993 Wang et al., 1993 Taniguchi et al., 1998,2000). 

Treatment 1 (substrate-only) was used as a baseline to test whether the snakes could use mouse-deposited substrate odors to relocate prey post-strike. To create substrate trails following the strike, the struck mouse was slid in one continuous motion, ventral surface down, along the base of the maze and out one of the two arms. The mouse was then removed from the maze so as not to present visual cues to the snake. Treatment 2 (airborne-only) presented snakes with airborne odors from struck mice to test whether snakes could relocate prey using only airborne information. To provide airborne cues, the struck mouse was placed in a wire-mesh basket, and that basket was placed on the intake side of one of the fans. The arm containing the odor was alternated fixrm one trial to the next. Treatment 3 (substrate vs. airborne) presented snakes with both substrate and airborne cues from struck mice to determine if there was a preference for one cue over the other. To present both substrate and airborne cues in concert, the substrate trail was deposited along the base and out one arm as in Treatment 1, and then the same struck mouse was placed in a wire-mesh basket on the intake side of the fan of the opposite arm. 

Lancaster, D. Wise, S. 1996. Differential response by the ringneck snake, Diadophis punctatus, to odors of tail-autotomized prey. HerpetoL, 52, 98—108. 

Identifying the specific cues which stimulate appetitive foraging behavior in snakes will enable the efficient development of an effective inanimate lure. Various snakes, including the brown tree snake, may use visual and/or chemical cues to locate distant prey (Eich-holz Koenig, 1992 Fritts, Scott Smith, 1989 Neal, Montague James, 1993 Rodda, 1992). For the brown tree snake, the cues that are reported as dominant vary between studies. Chiszar, Kandler Smith (1988) noted that visual cues alone would elicit attack behavior and that visual cues are important because if a lure container is visibly empty, attractive effects of chemical cues may be lost (Chiszar, 1990). However, Fritts et. al (1989) showed that brown tree snakes will enter traps baited only with bird odors (bird cage litter). 

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