From Ambush to Activity: Using Accelerometry to Reveal Cryptic Behaviors of Rattlesnakes and Kangaroo Rats

Abstract

In my first chapter, I review the behavioral characteristics, functional morphology, biomechanics, and taxonomic diversity of ambush hunting in snakes. Specifically, I discuss and review the decision-making process and behavioral stages involved in choosing an ambush site, the functional morphology and biomechanics behind the predatory strike of an ambush hunting snake, and what is known about the prevalence of ambush hunting within and between snake taxa.

In my second chapter, I propose a new method to quantify key aspects of the feeding behavior of three species of viperid snakes (Crotalus spp.) and assess the transferability of classification models across those species. I used open-source software to create species-specific models that classified locomotion, stillness, predatory striking, and prey swallowing with high precision, accuracy, and recall. In addition, we identified a low cost, reliable, non-invasive attachment method for accelerometry devices to be placed anteriorly on snakes, as is likely necessary for accurately classifying distinct behaviors in these species.

In my third chapter, I provide a proof-of-concept approach to effectively quantify behavioral patterns of small bodied (< 50 g), nocturnal, and terrestrial free-ranging mammals using large acceleration datasets by combining low-mass, miniaturized animal-borne accelerometers with radiotelemetry and advanced machine learning techniques. We developed a method of attachment and retrieval for deploying accelerometers, a non-disruptive method of gathering observational validation datasets for acceleration data on free-ranging nocturnal small mammals and used these techniques on Merriam’s kangaroo rats to analyze how behavioral patterns relate to abiotic factors.

We found that Merriam’s kangaroo rats are only active during the nighttime phases of the diel cycle and are particularly active during later light phases of the night (i.e., late night, morning twilight, and dawn). We found no reduction in activity or foraging associated with moonlight, indicating that kangaroo rats are actually more lunarphilic than lunarphobic. We also found that kangaroo rats increased foraging effort on more humid nights, most likely as a mechanism to avoid cutaneous water loss. My dissertation collectively provides a synthesis of ambush hunting in snakes and highlights the power of biologging technologies to overcome traditional challenges in studying cryptic and nocturnal species.