Diel Cycles in Chemosensory Behaviors of Free‐Ranging Rattlesnakes Lying in Wait for Prey

Abstract

The sensory ecology of foragers is fundamentally influenced by changes in environmental conditions such as ambient light. Changes in ambient light may hinder the effectiveness of particular senses (e.g., impaired vision at night), but many predators rely on multiple sensory systems and may continue to forage despite changes in light availability. Exactly how predator behaviors and sensory systems compensate under changes in light availability in the field is not well understood. We used radio telemetry and portable video surveillance cameras to quantify the sit‐and‐wait chemosensory foraging behavior of free‐ranging red diamond (Crotalus ruber) and northern Pacific (Crotalus oreganus oreganus) rattlesnakes during day and night periods. The two most common behaviors we observed were chemosensory probes, a behavior we describe in detail for the first time, and mouth gapes. During chemosensory probes, rattlesnakes extend their head beyond their coil, explore the surrounding area while tongue‐flicking, and subsequently return to a stationary position inside their coil. Foraging rattlesnakes probed at significantly higher rates during nocturnal vs. diurnal hours. Similarly, mouth gaping occurred during a higher percentage of nocturnal vs. diurnal hours for foraging snakes. Nearly half of all mouth gapes were followed immediately with a chemosensory probe, suggesting that mouth gaping also serves a chemosensory function in this context. Our results suggest that chemical cues play an increasingly important role in mediating rattlesnake foraging behavior at night. Examining how abiotic factors, such as light availability, influence the sensory ecology of free‐ranging predators is essential for accurately characterizing their interactions with prey.

Activity cycles and foraging behaviors of free-ranging sidewinder rattlesnakes (Crotalus cerastes): the ontogeny of hunting in a precocial vertebrate

“…For our analyses, we classified rattlesnakes into one of four behavioral states as follows: 1Ambush hunting: snake is coiled tightly on the surface or just inside the entrance of a burrow; snake remains motionless, with the exception of occasional chemosensory probing (movement of the head and neck out of the coiled position accompanied by tongue flicks, sensu Barbour and Clark, 2012a), mouth gaping (Burghardt, 1969;Graves and Duvall, 1983), non-rattling tail undulation (slow, rhythmic waving or wiggling of the tail in an otherwise motionless coiled snake, similar to caudal luring behavior employed by many viperid snakes sensu Heatwole and Davison, 1976), or striking at prey. (2) Moving: snake is actively moving on the surface between ambush sites.…”

“…Both adult and juvenile sidewinders exhibited a generalized mobile ambush foraging behavior typical of other Crotalus spp. (Clark, 2006;Barbour and Clark, 2012a;Putman et al, 2016), wherein individuals hunted via sit-and-wait ambush at a site for prolonged periods, interspersed with long-distance movements between sites (see Video 1 in Table 1; videos also available in the supplementary online Appendix). Snakes at our site, which were all monitored during the hotter summer months (May-August), sought refuge during the day, almost always in lizard or rodent burrows (we could not reliably distinguish between burrow types) and rarely in thick vegetation.…”

Does short-term provisioning of resources to prey result in behavioral shifts by rattlesnakes?

“…Individual ecological flexibility may be fixed in the neonatal or juvenile dispersal phase by genetic cues, imprinting based on experiences with different quality habitats and/or body condition; this may affect future development of behavioral syndromes (e.g., Madsen and Shine a , Davis and Stamps , Stamps et al ). The populations of adult western diamond‐backed rattlesnakes that we studied exhibited strong annual fidelity to foraging locations and had stable core‐use areas (Nowak ), a pattern observed in many desert rattlesnakes (e.g., Brown et al ; Barbour and Clark ; G. W. Schuett, Georgia State University, unpublished data). In our study sites, telemetered rattlesnakes often traveled from hibernacula in upland habitats to foraging locations in mesic or bajada habitats over fixed and predictable migration routes (Nowak and van Riper , Nowak , Nowak and Schuett ).…”

“…The lack of a group response to food and water provisioning may also reflect fundamental differences in energetic requirements and efficiencies between ectotherm and endotherm predators (Pough , Spotila and Standora ). These differences are expressed in life‐history parameters (Shine ), foraging strategies (e.g., Clark , ; Barbour and Clark ), and a lack of territoriality (Duvall et al , but see Huang et al ), which have important consequences for the ability of vipers to mount functional responses to changes in prey abundance (Nowak et al , Willson ). In the face of conditions demanding extreme energetic efficiency, snakes, and particularly large‐bodied vipers, have shown physiological and behavioral adaptations to tolerate extended periods of fasting (Lillywhite et al , McCue et al ).…”

A frontier in the use of camera traps: surveying terrestrial squamate assemblages

“…For example, to understand various rattlesnake ( Crotalus spp.) behaviours, authors of several studies first radio‐tracked target specimens to refuge locations (Clark , ,b; Barbour and Clark ,b; Clark et al. ).…”