In both systems, our initial focus has been on natural interactions, finding out how rattlesnakes and small mammals respond to each other during unmanipulated encounters.  We then use these findings on natural interactions to inform our experimental work.  Some of our initial findings are described in several recently published scientific papers:

GROUND SQUIRREL TAIL-FLAG DISPLAYS ALTER BOTH PREDATORY STRIKE AND AMBUSH SITE SELECTION BEHAVIOURS OF RATTLESNAKES

Barbour MA, Clark RW. 2012.  Proceedings of the Royal Society B Biological Sciences, 279:3827-3833.

ABSTRACT. Many species approach, inspect and signal towards their predators. These behaviors are often interpreted as predator-deterrent signals—honest signals that indicate to a predator that continued hunting is likely to be futile. However, many of these putative predator-deterrent signals are given when no predator is present, and it remains unclear if and why such signals deter predators. We examined the effects of one such signal, the tail-flag display of California ground squirrels, which is frequently given both during and outside direct encounters with northern Pacific rattlesnakes. We video-recorded and quantified the ambush foraging responses of rattlesnakes to tail-flagging displays from ground squirrels. We found that tail-flagging deterred snakes from striking squirrels, most likely by advertising squirrel vigilance (i.e. readiness to dodge a snake strike). We also found that tail-flagging by adult squirrels increased the likelihood that snakes would leave their ambush site, apparently by elevating the vigilance of nearby squirrels which reduces the profitability of the ambush site. Our results provide some of the first empirical evidence of the mechanisms by which a prey display, although frequently given in the absence of a predator, may still deter predators during encounters. [tail_flag_displays.pdf]

FIELD RECORDINGS REVEAL FACTORS THAT INFLUENCE PREDATORY STRIKE SUCCESS OF FREE-RANGING RATTLESNAKES (CROTALUS SPP.)

Clark RW, Tangco S, Barbour MA. 2012. Animal Behaviour 84:183-190.

ABSTRACT. Research on predator-prey interactions often focuses largely on prey behavior, treating predators as static danger, rather than as active behavioral participants that can respond adaptively to prey choices. A complete understanding of the functional significance of both predator attack behaviors and prey escape behaviors can only come from examining the interaction between both parties. For example, although the predatory strike of venomous snakes has been studied extensively in the laboratory, we have little understanding of the proximate factors influencing snake strike behavior under natural conditions. Here, we report details of the analysis of predatory strikes of free-ranging rattlesnakes (Crotalus spp.) towards their natural prey. We found that over half of strike attempts were unsuccessful, and the most significant factor influencing strike success was the ability of prey animals to initiate a rapid evasive dodge maneuver in the fraction of a second after snakes initiated strikes, but before snake strikes contacted them. Snakes, in turn, initiated strikes most frequently towards the flank of laterally moving prey, which is probably an attempt to counter the ability of prey to dodge strikes. [field_snake_strikes.pdf]

DIEL CYCLES IN CHEMOSENSORY BEHAVIOR OF FREE-RANGING RATTLESNAKES LYING IN WAIT FOR PREY

Barbour MA, Clark RW. 2012. Ethology 118:480-488.

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 surround- ing 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. [diel_cycles.pdf]

ROBOTIC SQUIRREL MODELS:  STUDY OF SQUIRREL-RATTLESNAKE INTERACTION IN LABORATORY AND NATURAL SETTINGS

Joshi SS, Johnson R, Rundus A, Clark RW, *Barbour M, and Owings DH. 2011. IEEE-RAM 18:59-68.

ABSTRACT. We describe a series of biorobotic squirrel models developed for the study of ground squirrel- rattlesnake interaction, both in the laboratory and in natural environments. These biorobotic models are unique in that they must interact with live, potentially hostile animals. Here, we describe our laboratory and field-ready robotic squirrels. Each of the models was built around taxidermically-prepared California ground squirrels, and contained separate control systems for tail flagging, body temperature maintenance, and tail temperature maintenance. The laboratory model was used for closed- loop laboratory experiments with 14 northern Pacific rattlesnakes, and helped confirm the first discovery of animal communication using infrared signaling. The field- ready robotic squirrels were redesigned for portability and deployment in rugged terrains, as well as enhanced video and data-logging capability. These models were field tested with live red diamond and northern Pacific rattlesnakes at two California field sites. Our robotic models are significant in that they have enabled controlled squirrel-rattlesnake studies of multi-modal communication. Some of these studies would be difficult, if not impossible, to perform without the robotics technology. [robosquirrel.pdf]

CURRENT STUDIES

We are now beginning to experimentally test some of the hypotheses and predictions laid out in the above papers.  To do this, we are conducting playbacks towards snakes using our biorobotic models, as well as simulating snake encounters toward small mammals and examining how their behavior shifts when they are in different behavioral states (e.g., either informed of the presence of a snake or not).  We are also working on several more publications that document additional findings.  These papers will be added to the site as they are published.