In a recent paper, in the Wildlife Society Bulletin, we compared three external transmitter methods for snakes: [1] glue-only (top left), [2] tape-and-glue (top right), and [3] the subdermal stitch method (bottom).
Radio telemetry is a widely used research tool that has allowed us to learn a lot about animal ecology, behaviour, and how to conserve them. Radio telemetry is used to track animals through habitats where researchers would otherwise loose them - mainly because most animals are sneaky, cryptic, and strive to exist in their habitats undetected.
In April 2012, we were planning a project that would involve us trying to learn about the habitat use and spatial ecology of Massasauga Rattlesnakes (Sistrurus catenatus) partnering with Magnetawan First Nation in Ontario. Before this we only had experience with radio tracking turtles, which are easy to attach transmitters to - you simply glue them to their shell! But, snakes presented a unique problem. They don't have shoulders, and no hips! So, a transmitter on a harness or belt would likely just fall off! Typically snake researchers internally implant transmitters, which requires anaesthesia and surgery. Yet, recent research has shown that internal implantation methods can increase snake mortality and infection rates, which may alter their natural behaviours or cause harm. So, as our study species of interest is a species-at-risk, we wondering if there were other options out there?
After some research, and chatting with colleagues, we came across a couple of methods to try out. During our first field season (2012), we began by using glue to attach transmitters to rattlesnakes. Unfortunately, we quickly learnt that the glue would dissolve in water! As you can imagine it was a poor option for this semi-aquatic snake that spends a large amount of time in wetlands. Luckily, we also tested another attachment method that used both tape and glue. Unfortunately, the tape-and-glue was also not as reliable as we hoped - transmitters often fell off snakes during skin shedding. Furthermore, this method resulted in skin irritations (see photo below) and slightly impeded snake movements. At the end of the first field season, we were still on the search for a viable alternative to internal transmitter attachment.
During the winter months, we came across another paper that described what seemed to be another promising external attachment method. This paper described the subdermal stitch method, which basically created a small piercing under the skin of the tail of the rattlesnake, threading a tie through this piercing, and then tying on the transmitter like a 'backpack'. Due to the issues we ran across in the last field season, we ran a pilot study over the winter in captivity using Corn Snakes. Then, due to the success of the pilot study - especially because the transmitter remained attached during the shedding - we used this method during our second field season (2013).
The subdermal stitch method, in both the pilot captive study and the field study, appeared very promising. The method did not cause significant skin irritation, rattlesnake movements and ability to rattle was maintained (see video below). Also, one of the female's with a transmitter attached successfully gave birth during our study (see photo below), which provided some evidence that this transmitter method does not effect rattlesnake mating, gestation, and parturition. Overall, our results suggest that the subdermal stitch method may be a viable external attachment method for snakes. But, it is important to note that our study was restricted in sample size, and we also did not test to see if any of these external attachment methods trigger immune responses, infections, or effects on snake fitness.
Can you find the mother rattlesnake above? [Hint: She is to the right of the grass tuft.] What about her 4 babies? The fact that this female rattlesnake successfully gave birth, while having a transmitter attached to her, suggests that the subdermal stitch method may not effect natural snake behaviours.
All in all, it was quite the journey learning about methods of externally attaching radio transmitters to snakes. And, one might ask, why you would ever want to follow a rattlesnake anyway? But, it is truely the only way to learn about the biology and behaviour of these really secretive, but fascinating creatures. It is very important to make sure that the information we are learning about these snakes is accurate, because it will be used to conserve these at-risk animals. So, internal implantation presents a problem for snake researchers - if the research method is making snakes sick, is the data collected viable? We are hoping that our, and future studies, about externally attaching transmitters to snakes may give snake researchers an alternative tool to use to get an accurate glimpse into the lives of the secretive, scaley creatures.
A Massasauga Rattlesnake
Article reference: Riley, J.L., Baxter-Gilbert, J.H., and Litzgus, J.D. 2017. A comparison of three external transmitter attachment methods for snakes. Wildlife Society Bulletin (doi:10.1002/wsb.748)
Detailed supplementary video that demonstrates the subdermal stitch attachment procedure we assessed in a pilot study & in the field, and appears to be a potential viable alternative for attaching transmitters to snakes.
