What threatens the blue racer snake on Pelee Island, ON?
Posted onOctober 1, 2023by, , ,
A blue racer snake. Photo: Gabriel Evans-Cook
This is the third installment of our series on the many facets of the blue racer conservation project on Pelee Island. You can check out the plight of the blue racer, what habitat blue racers prefer, and what is being done to build habitat.
Though once found elsewhere in Southern Ontario, blue racers in Canada are now restricted to Pelee Island in Lake Erie. This species is listed as endangered in Canada, primarily due to the impacts of habitat loss and degradation. Though there are other potential threats to the remaining blue racer population, such as road mortality and wild turkey predation, it isn’t fully understood how these potential threats impact the population and at what severity. This is an important knowledge gap to address for the recovery of blue racers in Canada, because once threats to the population are fully realized, mitigation strategies can be implemented where necessary to address them.
Assessing the threats of road mortality and turkey predation to the Pelee Island blue racer population.
As the name implies, road morality occurs when animals are struck on roads by passing vehicles. This is a common threat to reptiles and amphibians (known as herpetofauna) in Canada, especially in densely populated areas such as Southern Ontario. There are many reasons why herpetofauna use roads, some of which include:
To determine where and to what degree road mortality is occurring for blue racers and other reptiles and amphibians on Pelee Island, surveys have been conducted since 2020 by Scales Nature Park, University of Toronto, Natural Resource Solutions Inc. (NRSI), Ontario Nature, and Wildlife Preservation Canada. Road surveys consist of bicycling roads throughout the known blue racer range and recording the species, GPS location, and behaviour of any reptiles and amphibians observed. Surveys are carried out daily during the peak periods of activity for blue racers, including spring when snakes emerge from hibernation, and late summer when blue racers eggs typically hatch. The road survey data will be mapped and analyzed to identify road mortality hotspots for blue racers and other species at risk on Pelee Island.
Though native to North America and a common site on the Ontario mainland, wild turkeys are non-natives to Pelee Island and were introduced in 2002. As omnivores, the diet of wild turkey includes plant matter, invertebrates, and small vertebrates. Wild turkeys have even been documented preying on herpetofauna, such as salamanders, lizards, and small snakes! Given their generalist diet, it is possible that wild turkey negatively impact the Pelee Island blue racer population by preying on hatchlings and juveniles. However, whether wild turkeys on the island are eating blue racers is unknown.
To start to answer this question, a multi-disciplinary team from Wildlife Preservation Canada, Natural Resource Solutions Inc. (NRSI), African Lion Safari, and Queens University developed a technique to test wild turkey scat for the presence of blue racer DNA. Since all the food a turkey has eaten will be present in its scat, these samples should contain traces of blue racer DNA if the turkey has been eating blue racers. During the 2022 season, 8 samples of turkey scat were collected. In order to identify blue racer DNA from the other matter stored in the crops or scat, the researchers developed a specific set of primers (short DNA segments) and probe (short DNA segment with a reporter dye) designed to target and emit fluorescence when binding to a unique section of blue racer DNA. The number of copies of that DNA is therefore proportional to the fluorescence signal and was estimated using an approach called droplet digital Polymerase Chain Reaction (ddPCR). When tested with the DNA of other Ontario snake species, the primers and probe worked and successfully identified blue racer DNA, even at low amounts.
When the contents of the 8 scat samples were tested, no blue racer DNA was found, however, this does not necessarily mean that wild turkeys are not preying on blue racers. There are many other reasons that could explain why no blue racer DNA was found in the samples, including:
Ideally, with continued funding, many more scat samples could be collected throughout the field season in more targeted areas, capturing turkey diets at various times of the year. Evidence of blue racer DNA in these samples will allow researchers to determine if wild turkeys are in fact predators of blue racers. This new DNA-based tool can also be applied for investigating other factors affecting blue racers. For example, it can be used on water or soil samples in the future to help quantify blue racer habitat suitability and site occupancy to help preserve the imperiled Canadian blue racer population.
Wild turkey in a field. Photo: Orianne Tournayre
Assessing the threat of road mortality and turkey predation to blue racers on Pelee Island is an important step in protecting the remaining population. This work will answer several key questions, including what is affecting the persistence of blue racers on Pelee Island, where it is occurring, and at what severity the population is impacted. With this information, targeted mitigation strategies can be implemented to lessen the impact of these threats to the Pelee Island blue racer population and help prevent further declines.
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