Protecting the Midget Faded Rattlesnake

Historically, the Midget Faded Rattlesnake was known to be a rare species across their range which includes Utah, Colorado, and Wyoming (see range map for the Midget Faded Rattlesnake). More recent studies indicate that while they may not be particularly rare, they do exist at lower population densities and seem to be more vulnerable to disturbances associated with land use and development especially since their geographic range is rich in fossil fuels, wind energy, and recreational use. What makes them so vulnerable are their fundamental differences in habitat use compared to other rattlesnakes due largely to their habitat specialization. Midget Faded Rattlesnakes would best be described as a high elevation, canyon species. As a high elevation species, the climate is more extreme with short activity periods and long, cold winters. For the midget faded rattlesnake, this means less time to grow, less time to find food and mates, and less habitat suitable for hibernation (cracks deep enough to stay below the frost line for 6-8 months).

The Wyoming Game and Fish Department and the Wyoming regional Bureau of Land Management have had a special interest in the conservation of Midget Faded Rattlesnakes since the mid-1990s when one of their concerned biologists questioned the sustainability of a collection permit application asking for 200 gravid females. Since then, both the Wyoming Game and Fish Department and BLM have taken the initiative to determine their population status, to ensure their protection against such collection as well as protection from the deleterious effects of energy development and recreation. The species is now permanently protected from collection across their range in all three states.

In 2009, the Orianne Society began its conservation efforts in Wyoming for the Midget Faded Rattlesnake with the Wyoming Game and Fish Department in partnership with Idaho State University, Clayton State University (Morrow, GA), and the University of Idaho. The goals of this study were to develop predictive models that could accurately predict the presence of Midget Faded Rattlesnakes and their denning habitat, as well as use landscape genetics modeling to better understand their population dynamics and status. We are pleased to announce the completion of our models last year that will serve as a powerful tool for conservation and management decisions in Wyoming. The final predictive model proved to be 85% accurate in predicting the presence of Midget Faded Rattlesnake denning habitat so that managers can better evaluate land use and development that could have negative impacts on their populations. Also, the landscape genetics revealed just how susceptible they are to disturbance in general and that roads are likely the greatest threat (including small dirt roads that service energy development facilities). Our next goal was to secure funding to extend our models down into the Colorado portion of their range. Their range includes much of the western slope of the Rocky Mountains in CO. Regional BLM offices in that area teamed up and came forward with their interest and funding for a 2-year study that will allow us to realize this goal.

The Wyoming models were generated with copious amounts of habitat use data collected across the range of Midget Faded Rattlesnakes in Wyoming. There are elevational and latitudinal differences in the CO range that could mean variation in habitat and habitat use but the Wyoming data will serve as a good starting point to develop preliminary models based on the similarities in CO since there have been no formal studies of the species in this part of their range. Any differences in habitat use, landscape and climate can be accomodated in the model with the data we will collect in CO over the next 2 years. We will begin preliminary model development as we did in Wyoming, but applying the Wyoming habitat use data to the CO range. These preliminary models will provide us with random points across the CO range with a spectrum of probability scores that we will then validate in the field. The probability scores represent how likely it will be that Midget Faded Rattlesnakes are present at the random points and then we will report back to the model whether we found snakes or not. We generate the models using GIS layers that represent those features of the habitat and climate most correlated to the presence of Midget Faded Rattlesnakes. In all, we will be developing 4 candidate models based on these variables and so that we can test them all at the same time, we will use these 4 models to create a single ensemble model with 5 categories. Those 5 categories are based on how many of the 4 models predict the presence of Midget Faded Rattlesnakes between 0-5 (0 meaning that none of the 4 models predicted presence and 5 meaning that all 4 models predicted presence). Also, we will be focusing on denning habitat since this is the most critical habitat for a population.

One of the challenges in this study is the fact that the range of Midget Faded Rattlesnakes in CO is an order of magnitude greater than that in Wyoming (see range map for the Midget Faded Rattlesnake). This means much more land to cover, more man hours, and a longer period for data collection (but who can complain when that translates to a lot of hiking in the beautiful Rocky Mountains of Colorado all the while looking for my favorite little rattlesnake!). As a result, we plan to collect an order of magnitude more data compared to the data we collected for the Wyoming models. This will ensure that the predictive power of the CO model rivals that of our Wyoming models. This study will focus entirely on the development of predictive models so that managers can have a powerful tool to help protect Midget Faded Rattlesnakes against increasing energy and land development as in Wyoming. As long as we will be encountering Midget Faded Rattlesnakes, we will obtain permits to collect morphometric data, and blood or other non-invasive tissues for genetic analysis at a later time.

We will also be collaborating with Dr. Stephen Mackessey of the University of Northern Colorado in a venom study. Dr. Mackessey studies the composition of snake venoms for a variety of reasons from the ecological to its application in cancer research. Like most of us, Dr. Mackessey has a fondness for Midget Faded Rattlesnakes and jumps at any opportunity to see them in the field and extract their venom. We will be using some of their venom for a population level analysis to determine differences in venom composition across their range. We collected a good sampling of venom across their range in Wyoming last year and it will be nice to do the same in CO for a more comprehensive study.

Our future goals of course will be to extend our predictive models into the greatest part of the Midget Faded Rattlesnake range, Utah. Over the next 2 years we will be seeking interest and partners there to complete our modeling of the entire range of the species! All 3 states are receiving increasing interest in energy development and our models will help them minimize any direct and/or indirect threats to Midget Faded Rattlesnake populations.