Radio-telemetry has, for years now, been one of the most essential tools for studying the natural history and spatial ecology of snakes (Ward et al. 2013). However, this technique is limited in various ways. Tracking is dependent upon being within a close range of the animal, and then visually locating the animal. There is evidence that coming into close proximity with radio-tracked snakes affects behavior (Parent and Weatherhead, 2000; Ward et al. 2013). Radio-telemetry is also limited to gathering data at times when snakes can be tracked, making it very difficult to collect data at night and between tracking events. Most studies using radiotelemetry track snakes every one to three days, and even when tracking there is often a physical limit to how many snake locations can be accessed. Another down side to radiotelemetry is that signal transmission can only reach so far.
Radio tracking still produces valuable data, however advances in technology have provided other tools for wildlife tracking that have the potential to resolve some of the above mentioned limitations. Among these, the use of GPS has emerged as a viable option for wildlife tracking. (Cognacci et al. 2010; Tomkiewicz et al. 2010; Ward et al. 2013). GPS tracking has several advantages over radiotelemetry. One such advantage is continuous data transmission through a number of mediums (cellular, bluetooth, and wi-fi). Moreover, the ability to obtain position time series data representing movement paths affords biologists more data and greater insights into the spatial ecology of organisms (Nathan et al. 2008). Position time data can now be obtained from a distance without disturbing the animals being tracked. Some GPS units, such as those that I will be using, have a “smart GPS” function, which logs position time data only when the animal moves a specified distance! The possibilities for field based applications are endless with this type of technology.
Automated receiving units (ARU) have been used as an alternative to radiotelemetry in several snake studies, but have, in some cases, reported estimated accuracy of positions to 42 meters (Ward et al. 2013). Furthermore ARU is extremely expensive and can produces unreliable data as a result of “postural” changes in snakes and more.
Currently, GPS has been miniaturized to the point of telemetry, and thus is an option for tracking much smaller animals. This method has been applied to various mammalian and avian taxa (Tomkiewicz et al., 2010), however very little GPS tracking has been done with Squamates. Ashleigh Wolfe, a PhD student at Curtin University, recently tested GPS tracking on Pseudonaja affinis and experienced relative success in obtaining data (Wolfe personal correspondence, 2016). Wolfe implemented an attachment technique following that described by Ciofi and colleagues (1991), who also successfully gathered data from snakes with externally attached tracking units (radiotelemeters in this case). Ernst (2003, 2004) attached radio transmitters to the rattles of Prairie Rattlesnakes, Crotalus viridis. Rattle attachment is not a novel technique, but it’s never been done with GPS transmitters! GPS has the potential to once again revolutionize the field of wildlife biology. Now that the technology exists, the next step in snake tracking is to incorporate GPS.