Houston ChandlerViews:
As many readers will know, Eastern Diamond-backed Rattlesnakes are currently the focus of significant conservation concern. The species has been petitioned for federal listing under the U.S. Endangered Species Act, and U.S. Fish and Wildlife Service is currently working on a Species Status Assessment to inform the listing process. This document will provide an overview of the species’ natural history and, more importantly, an assessment of current knowledge about the status and future threats to extant eastern diamondback populations.
Eastern diamondbacks have declined for many of the same reasons as other reptiles in the southeast (extensive loss of habitat, fragmentation of remaining habitat by roads, and loss of natural fire regimes). However, eastern diamondbacks also face additional pressures from widespread, wanton persecution by humans (both from individual incidents and targeted rattlesnake roundups). Although much of the targeted roundup pressure has been removed in recent years, eastern diamondbacks continue to face an uncertain future in much of their range. In addition to continuing habitat loss, degradation and persecution, emerging threats related to disease (Snake Fungal Disease; Steeil et al. 2018) and invasive parasites (pentastomes; Walden et al. 2020) are cause for concern.
The Orianne Society has worked with eastern diamondbacks in various capacities since 2010 when they were incorporated into our annual monitoring for Eastern Indigo Snakes (Bauder et al. 2017). Over this period, we have also marked eastern diamondbacks on the Longleaf Stewardship Center and sampled many individuals as part of our Snake Fungal Disease inventory across southern Georgia (Haynes et al. 2020). Perhaps more importantly, eastern diamondbacks have been one of our foremost venomous snake species displayed during countless education events.
To support current conservation efforts, we have been working with the Fish and Wildlife Service to develop a range-wide habitat suitability model for eastern diamondbacks (similar to our recent indigo snake project; Chandler et al. 2022). Such models can be important tools for making landscape-scale planning decisions. As part of this effort, we have been building a database with observations of eastern diamondbacks from across their distribution. Maybe you have submitted records for this process? We have also conducted extensive surveys on the Longleaf Stewardship Center in an effort to generate more mark-recapture data. Finally, eastern diamondbacks have a large range, expanding across a wide variety of public properties in the southeast. We have conducted surveys for eastern diamondbacks across a variety of properties in southern Georgia that should support populations but do not have any confirmed observations.
To date, we have acquired observational data from every state within the eastern diamondback range, including from state and federal agencies, museum collections, other NGOs, collaborators working at various sites, and through many submissions from the general public. The database currently has over 5,000 records, and we plan to collect additional records through October 2023. Excitingly, this includes records from two conservation properties in southern Georgia where eastern diamondbacks had not been previously documented. On the Longleaf Stewardship Center, we have marked 14 individuals over the last year, in addition to 22 individuals that were already marked. Despite significant survey effort (26 survey days), we have managed to recapture only 2 individuals! Unfortunately, low recapture probabilities makes it challenging to estimate important demographic parameters (survival, population size) that are the ultimate goal, but building a base of marked snakes should lead to increased recaptures over time. There are apparently more eastern diamondbacks present on the Longleaf Stewardship Center than any of us would have guessed when the project started.
Our focus is now shifting to building the habitat model using the data collected from the above efforts. This process involves collecting a lot of spatial data that we think is important for defining eastern diamondback habitat or lack thereof. Things like the amount of upland habitat, the amount of development, or the fire frequency in recent years will certainly be important. Environmental data collection will continue as our field efforts wind down, and we plan to finish the habitat model analysis by the end of 2023 or beginning of 2024.
Regardless of the outcomes of the federal listing process, eastern diamondbacks will likely continue to decline in many locations throughout their range, especially where populations are not supported by protected or managed landscapes. The recent disease and parasite issues (as well as continued persecution) also provide concern for populations in otherwise protected landscapes. Increased conservation focus on eastern diamondbacks can help to mitigate these and other threats. Unfortunately, venomous snakes face an uphill battle in the eyes of many, despite the benefits that such species provide (Kaby et al. 2013; Reiserer et al. 2018). Implementing effective conservation and protection measures will require long-term efforts to understand eastern diamondback ecology and work towards changing public perceptions on rattlesnakes. Eastern diamondbacks are, without a doubt, one of the most charismatic animals that call the southeastern U.S. home. They are an important part of our natural history, and we will continue to work towards the conservation of North America’s largest rattlesnake.
Literature Cited
Bauder, J.M., D.J. Stevenson, C.S. Sutherland, and C.L. Jenkins. 2017. Occupancy of potential overwintering habitat on protected lands by two imperiled snake species in the Coastal Plain of the southeastern United States. Journal of Herpetology 51:73–88.
Chandler, H.C., C.L. Jenkins, and J.M. Bauder. 2022. Accounting for geographic variation in species-habitat associations during habitat suitability modeling. Ecological Applications 32:e2504.
Haynes, E., H.C. Chandler, B.S. Stegenga, L. Adamovicz, E. Ospina, D. Zerpa-Catanho, D.J. Stevenson, and M.C. Allender. 2020. Ophidiomycosis surveillance of snakes in Georgia, USA reveals new host species and taxonomic associations with disease. Scientific Reports 10:10870.
Kabay, E., N.M. Caruso, K. and Lips. 2013. Timber rattlesnakes may reduce incidence of Lyme disease in the Northeastern United States: Ecological Society of America Annual Conference, 98th, Minneapolis, Minnesota, August 4–9, 2013.
Reiserer, R.S., G.W. Schuett, and H.W. Greene. 2018. Seed ingestion and germination in rattlesnakes: Overlooked agents of rescue and secondary dispersal. Proceedings of the Royal Society B 285:20172755.
Steeil, J.C., K.L. Hope, M. Evans, A. Peters, and A. Cartoceti. 2018. Multifocal Ophidiomyces ophiodiicola infection in an Eastern Diamondback Rattlesnake (Crotalus adamanteus) without the presence of skin lesions. Journal of Herpetological Medicine and Surgery 28:76–80.
Walden, H.D.S., M.E. Iredale, A. Childress, J.F.X. Wellehan, Jr., and R.J. Ossiboff. 2020. Case report: Invasive pentastomes, Raillietiella orientalis (Sambon, 1922), in a free-ranging Banded Water Snake (Nerodia fasciata) in North Central Florida, USA. Frontiers in Veterinary Science 7: 467.
