Habitat selection of northern Pacific rattlesnakes

Habitat selection of northern Pacific rattlesnakes

For my Master's program I attended Humboldt State University and under the supervisor of Dr. Sharyn Marks I developed a project studying the habitat selection of northern Pacific rattlesnakes (Crotalus oreganus oreganus) at multiple spatial scales. I used the knowledge of a local expert, the late Dr. Lowell Diller from Green Daimoind Recourses Company, to locate a couple of rattlesnakes hibernacula (rocky outcrops that rattlesnakes lay dormant in during the winter months). Later, after scouring the surrounding hillsides on my own I located a total of 22 hierbancula. I conducted most of the fieldwork on my own and relied on the assistance of volunteers in my first season and four undergraduates working for me for credit during my second season. I had my fair share of adventure including close encouters with elk, bears, mountain lions, illegal cannabis growers, and of course rattlesnakes. Once field data were collected, I use paired-resource selection functions to analyze microhabitat differences between hibernacula and nearby outcrops that were unoccupied. I found rattlesnakes preffered outcrops that faced due south (180 degrees from North), had more large talus (rocky rubble surrounding the outcrop), and less vegetative cover. At one point, I brought a committee member, Dr. Mark Hemphill-Haley a professor in geology, with a team of undergraduates to conduct geological surveys of the outcrops. They immediately noticed that all hibernacula were located within the head scarps of landslides, which ended up being a significant result form my research.

To assess habitat selection at a regional scale I used Maximum Entropy (MaxEnt) modeling methods. I generated a series of MaxEnt models at two spatial scales: northern California and just the northern California coast. I showed that maximum annual temperature in March, mean precipitation in March, and elevation were the key physical and climatic features influencing rattlesnake habtiat selection. These models also showed that the northern coast of California was significantly less suitable than the rest of northern California, making it a marginal habitat. Together with my analysis of hibernacula selection I concluded that common occurrence of landslide triggers (e.g., heavy rainfall, earthquakes, construction activitied) along California's north coast creates an abundance of suitable hibernacula providing rattlesnakes an escape for the marginal conditions of the macroclimate.

During my Master's I developed my analtical foundation that has allowed me to develop an eleborate analytical toolbox including both spatial and non-spatial statistical methods. I was also asked to serve as a Teaching Assistant (TA) in my first semester and discoverd I had a knack and passion for education. I ended up teaching more and more each semester until in my final semester I was teaching four lab sections for two lasses. Every year I would lead field trip with Dr. Marks and Dr. Diller to my hibernacula to give demonstrations to the Herpetology class on rattlesanke handling, sexing, pit-tagging, and taking general body measurements. My passion for education spilled out of the classroom and I found myself giving lectures at the Eel River Society's Earth, Water, and Fire day in 2016 and led field trips to my rattlesanke hibernacula for boy scout troops and firefighters. I was also blessed with cooperative landowners, which made my fieldwork possible. Green Daimond owned some of the land, but three private ranches, (Bing Bend, Clouds Rest, and Hunters) in Maple Creek, CA provided land access. The ranchers at Big Bend were beyond generous, feeding me after long field days, providing me with housing in the field, and employment opportunities around the ranch.

Visit Humboldt County, California at least once in your life.

Hecker, L.J., W.T. Bean, and S.M. Marks. 2020. Compensatory microhabitat selection by Northern Pacific Rattlesnakes (Crotalus oreganus oreganus) in an atypical rattlesnake habitat.Journal of Herpetology. 54(1):39-49.

My showing a Humboldt State University Herpetology student how to insert pit-tags into a northern Pacific rattlesnake (Crotalus oreganus oreganus).