The overwintering ecology of a cold-adapted and refugia-dependent rattlesnake

My dissertation examines several behavioral strategies used by refugia-dependent reptiles, focusing on imperiled Timber Rattlesnakes (Crotalus horridus), to successfully navigate and survive harsh temperate winters. My findings expand on previous work on the overwintering strategies of C. horridus and provide insights into the ecology of refugia-dependent snakes valuable for conservation, management, and further study. In the first data chapter (chapter two), I identified the overwintering habitat characteristics of C. horridus in Illinois and determined the distribution of likely hibernacula habitats throughout the state. Using habitat suitability modelling, I identified slope angle, topographical position index, forest patch area, and aspect as important drivers of hibernacula habitat. Together, the variables and site surveys suggest suitable overwintering habitat for C. horridus in Illinois is distributed primarily in southern Illinois and throughout the Mississippi and Illinois River border counties. My findings add to the current understanding of the species' overwintering requirements and provides a foundation for future ecological studies, management, and survey efforts to find new hibernacula throughout Illinois. In the second data chapter (chapter three), I identified environmental cues of spring emergence for C. horridus to determine the species' emergence phenology and examined the applicability of identified cues in predicting emergence across the species' range. The most parsimonious model for predicting spring emergence included the additive effects of maximum daily temperature, accumulated degree days, and latitude. With notable exceptions in the southeastern U.S., the model accurately predicted the average emergence day for eight other populations range-wide, emphasizing the importance of temperature in influencing the phenological plasticity observed across the species’ range. The apparent broad applicability of the model to other populations suggests it can be a valuable tool in predicting spring emergence phenology. In the third data chapter (chapter four), I demonstrated the existence, phenology, and likely purpose of the fall and spring transient periods— “transitional” periods between summer and overwintering periods— for C. horridus in west-central Illinois. My results suggest the transient periods can last upwards of a month, are phenologically flexible in response to variable annual temperatures, and serve as necessary buffers to ensure snakes have reliable and swift access to refugia when temperatures surpass lower thermal tolerances. Spring transient periods result from post-emergent snakes waiting at overwintering sites for a second thermal trigger—alongside the initial cue for egress—which signals the arrival of consistently warm temperatures appropriate for summer activity. Fall transient periods result from snakes intentionally arriving at refugia at higher temperatures to avoid being caught in summer habitats when temperatures fall below thermal limits. My findings complement and expand previous work on the overwintering strategies of C. horridus and provide further insights into an understudied, but important, aspect of the annual life cycle of refugia-dependent and migratory snakes.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Jesper, Andrew Charles Ben

Contributors dc:contributor

• Dreslik, Michael J
• Ward, Michael P
• Suski, Cory D
• Crawford, John A
• Eckert, Scott A

• Hibernation
• Brumation
• Pitviper
• Crotalus Horridus
• Timber Rattlesnake
• Habitat Suitability Model
• Species Niche Model
• Hibernacula
• Refugia
• Transient Habitat
• Stopover Habitat
• Spring Emergence
• Spring Phenology

Statement dc:rights

• Copyright 2024 Andrew Jesper

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/125579

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F125579