Managing Forests with Rattlesnakes in Mind

This week we have a guest writer, Andrew Hoffman, a Ph.D .student at Ohio State University. Andrew is part of the Peterman Lab, led by Dr. Bill Peterman. The Peterman lab is conducting research on timber rattlesnakes. We are excited to share their story with you. 

And now a word from our guest…

Persecution and unregulated forest clearing resulted in the near-extirpation of Ohio’s timber rattlesnakes. Ironically, regulated timber harvests may be the very thing that kept them around. Timber rattlesnakes once occurred in suitable habitat throughout most of Ohio, but populations are now centered on only a handful of State and Federal Forestry lands. These properties are the largest remaining forested lands in the state, but they exist because of timber resource needs. The fate of the timber rattlesnake in Ohio is now intricately linked with forest management practices, a situation that is mirrored in many other states.

​During 2016, we began capturing and implanting radio-transmitters into timber rattlesnakes in southeastern Ohio to study their movement patterns and habitat use in a landscape with a long history of varied management practices. We are now in our third field season with movement data collected for 35 snakes (currently tracking 27) and have learned quite a lot! Below, I’ve listed a few of our findings:

One of our largest males catches some sun on a fallen log

Denning Behavior – Timber rattlesnakes are known for congregating at large, communal overwintering dens in and around rocky outcrops and cliffs, but snakes at our site behave quite differently. The 27 snakes we are currently tracking use 18 different den sites, and many appear to den alone. Moreover, most of these dens are nondescript holes on forested slopes with variable aspects. We also rarely see snakes at our study site basking near their dens (even on remote, time-lapse cameras). Though this may mean overwintering habitat is not limiting in southern Ohio, it makes it difficult to predictively model and locate unknown dens. We are also interested in when spring emergence happens and how snakes use the landscape during April, as this is the time when foresters conduct prescribed burns.

A nondescript rattlesnake den at our study site on a forested slop

Snake Fungal Disease (SFD) – The emerging fungal pathogen Ophidiomyces ophidiicola is, at best, a stressor on many North American snake populations and, at worst, a real threat to many species, especially pit vipers. We confirmed the presence of this pathogen in 2017 and again in 2018. Of the eight snake mortalities we’ve observed, four tested positive for this pathogen prior to death. Though some of these snakes were not symptomatic and were presumably predated, we are confident that SFD played a role in the death of at least two snakes. Though SFD clearly is a stressor in our population, five SFD-positive snakes remain healthy and have not shown symptoms of the disease. One large SFD-positive male was healthy during 2016, emerged during 2017 with numerous lesions, and went on to seemingly fully recover from the disease by the fall after a year of reduced movements and repeatedly shedding. We will continue swabbing our study animals biannually for SFD and monitoring the movements and habitat use of affected snakes in hopes of better understanding the effects of this disease on timber rattlesnakes in the wild.

A female in our study displays the characteristic facial lesions of Snake Fungal Diseas

Habitat Use – The question at the core of our study is how do different forest management practices affect the way timber rattlesnakes use the landscape? This is a multi-faceted and complex question that requires data on important resources for the snakes (e.g. food and thermally suitable sites), movement and habitat use data, and landscape/habitat metrics for the property. Though much of this work is still under way, our preliminary analyses are beginning to paint a picture for us. The figure below is taken from one of our recent poster presentations and highlights the variability we see at our site. Most snakes appear to be using disturbed habitats (sites that were previously cut or burned) more often than expected given their availability, but some snakes appear to avoid disturbed sites. In the future, we plan to use more detailed GIS data and more extensive telemetry data to determine whether certain management regimes result in habitat that snakes use preferentially and to what degree sex, body condition, and time of year dictate patterns of habitat use.

Though we still have a long way to go to better understand how forest management is affecting rattlesnakes in Ohio (and beyond), we are encouraged by how robust our study population appears to be and that snakes use both heavily disturbed, young woods and relatively mature forests extensively. We also try to engage in as many outreach events as we can, including programs to help educate the general public, landowners, and forest managers about this remarkable species! If you want to follow the lives of the snakes we are tracking, check out our Twitter feed @TimberTweets.

An adult female catches some rays in the waning days of fall 2017