Feral swine are among the top one-hundred worst alien invasive species in the world (Lowe et al., 2000). We know that they have the potential to destroy natural ecosystems and agricultural crops. Feral swine also pose a significant risk for transmission of domestic, transboundary and public health diseases. Feral swine are able to invade and then occupy remote habitats that have relatively low human densities. Recent expansion of feral swine into new territories in Northern Europe and Asia has made it clear that feral swine could rapidly expand and establish populations in the northern United States and Canada.
Unfortunately, low density populations of feral swine are difficult to detect in the northern latitudes of North America .Standard techniques for detecting feral swine rely on reports from the public and through field investigations including aerial surveys, trail camera monitoring, baiting, radio-telemetry, and intensive field searches for signs such as tracks, feces, wallows, and rooting. To make matters worse these traditional surveillance methods are labor intensive, costly, and do not consistently produce reliable information about the status of feral swine at low densities.
Satellite telemetry data collected from collared feral swine documented large-scale and frequent movements, large home ranges, and extensive use of wetlands, including animals frequently wallowing near open water as well as crossing open water (Gray, 2019). Environmental DNA (eDNA) has been used quite a bit to detect aquatic species in waterways and has occasionally been used for detection of terrestrial species such as coyote. These Michigan researchers wanted to determine if environmental DNA sampled from a water shed could detect feral swine in downstream water samples. This would be very useful in thickly wooded areas that are difficult to access even with the use of an ATV. A novel E-DNA assay was developed incorporating molecular methods. From August 2017 to April 2018, water samples and stream data were collected along 400 meter transects in two different stream types where swine DNA was artificially introduced to investigate potential factors affecting detection.
Detection probability for swine DNA negatively related to water temperature (β = – 0.21, 95% CI [-0.35 to -0.09]), with the highest detection probability (0.80) at 0 °C and lowest detection probability (0.05) at 17.9 °C water temperature. Results indicate that sampling for swine eDNA in free-flowing stream systems should occur at lower water temperatures to maximize detection probability.
Take Home Messages:
- Techniques for utilizing eDNA are showing potential as a viable alternative to traditional methods of monitoring a terrestrial invasive species such as feral pigs in northern regions of the United States and Canada.
- Currently there are fewer issues with feral pigs in Ontario than there are in the USA and Western Canada. Keeping it that way will require early detection of change.
Ref: Hauger AN, Hollis-Etter KM, Etter DR, Roloff GJ, Mahon AR. Use of environmental DNA (eDNA) in streams to detect feral swine (Sus scrofa). PeerJ. 2020 Jan 2;8:e8287. doi: 10.7717/peerj.8287. eCollection 2020.