Monitoring threatened, endangered, at-risk species (TES) across roughly 25 million acres that are, at times, inaccessible due to mission activities is challenging for the Department of Defense (DoD), especially when those species are by definition rare and exhibit secretive behaviors like snakes. Habitats managed on DoD lands support 131 snake species, five of which are currently listed as TES by the U.S. Fish and Wildlife Service, 2-3 more are awaiting a listing determination, and at least two have been petitioned for listing recently. These TES snakes require Endangered Species Act compliance monitoring at more than 30 installations and the number is growing. Traditional monitoring methods for these species (e.g., visual searches, traps) require repeated installation access, which increases opportunities for mission conflict and non-compliance. To mitigate this conflict, an automated monitoring approach was developed to detect snakes and track individuals remotely. The objective of this project is to demonstrate the full-scale potential of this emerging automated monitoring technology by measuring recovery of a reintroduced population of the federally threatened Eastern Indigo Snake (EIS, Drymarchon couperi).

The monitoring approach combines Automated Tag Recorders (ATR), camera traps, and drift-fence sampling arrays to detect both untagged EIS and those tagged with a Passive Integrated Transponder. Each ATR-camera array includes an inverted five-gallon (18.9L) bucket with a game camera mounted inside facing the ground, and two 100ft (30.5m) drift fences extending in opposite directions. Each bucket has two openings cut into the sides that align with the fences so snakes traveling along the fence can pass through the inverted bucket. The game camera mounted inside the bucket is programmed to take three pictures, one-second-apart, whenever the camera’s infrared sensor is triggered by the motion of a snake passing through. An ATR shallowly buried in the ground directly under the game camera allows tagged snakes to be detected and recorded while passing through the bucket. Because all EIS are tagged prior to release in the reintroduced population, the detection of any untagged EIS individuals with cameras would be evidence of wild-born individuals in the reintroduced population. The expectation of positive population growth within this automated monitoring framework would be an increase in untagged individuals detected over time and space.

The EIS is a high priority species under the DoD and Department of the Interior’s Recovery and Sustainment Program (RaSP), which identifies species whose recovery is critical to long term mission sustainment. Evidence of EIS population growth and spread in the reintroduced population provided by the automated monitoring approach described above would meet all of the RaSP objectives for this species. With EIS occurring or potentially occurring on as many as 31 DoD installations, the potential benefit of automated monitoring tools to DoD in terms of impact and cost is great. With respect to impact, the automated monitoring technology will reduce regulatory conflict with mission activities, because the ATR-camera arrays can continue to monitor in areas with heavy mission activity. In terms of cost, the ATR-camera arrays should decrease annual maintenance costs enough compared to traditional methods to compensate for greater implementation or start-up costs. The full-scale cost analysis will determine the return on investment, time to payback, and estimated life-cycle cost of the automated technology compared to traditional monitoring methods for this species.