Author: Jody Tucker, U.S. Forest Service, Pacific Southwest Region Carnivore Monitoring Program
Figures below text in order (Fig 1 first)
For over 20 years, the biologists in the western United States have used track plates as a simple and cost-effective method to survey for carnivores, in particular fisher (Pekania pennanti) and Pacific marten (Martes caurina). Both are species of conservation focus in the region with the southern Sierra Nevada fisher population recently listed in June 2020 as endangered under the federal Endangered Species Act
Figure 1 (Clockwise from top left). A fisher detection at a baited trail camera station; Closeup of a fisher front foot; Track-sheet from a fisher detection at a track plate station; and a baited track plate station including a barbed wire hair snare to collect genetic samples.
Track plate surveys use metal plates covered partially with some type of ‘ink’ (such as printer toner, chalk, or soot applied with a torch) placed inside a baited box to collect high quality animal tracks as an individual walks across the plate to access the bait. Tracks are collected on white contact paper which can be easily stored long term to provide an archive of detections.
While fisher and marten tracks can be reliably identified to species there is currently no accepted method to identify sex or individuals limiting data analytics to only presence/absence methods (i.e. occupancy estimation). Recently the U.S. Forest Service has partnered with Wildtrack to develop Footprint Identification Technology (FIT) to identify sex and individuals using track plate footprints.
FIT is a species specific tool. Each species has a unique foot structure and footprint, and the first step in developing FIT for a new species is to develop a reference or training library of footprints to build a species-specific FIT classification algorithm. While FIT usually involves collecting a reference track set from captive animals, few fisher and marten are present in zoos. Consequently, we are using a novel, non-invasive approach for our reference data by using genetic identification of individuals from hair snares deployed at track plate sites. Individual track images from genetic recaptures are imported to a feature extraction tool in JMP developed for fisher by Wildtrack.
Figure 2. Example of the Wildtrack feature extraction tool for fisher using JMP software. Reference points are applied to the centroids of fisher trackpads to derive a suite of morphological measurements for each track to use in FIT analysis.
FIT offers the potential to expand the scope of both archived and newly collected track plate data from only species presence/absence to individual and sex providing more detailed data to inform wildlife management and conservation. Additionally, as many management guidelines are focused on protection of reproductive females, being able to identify females is a critical tool needed to better inform management decisions. FIT can also be used to match individual animals to their unique footprints providing an opportunity for ongoing monitoring of individual movement and thus population demographics and ecology.
Figure 3. Example of hierarchical clustering analysis identifying the number of fishers based on track ID and which tracks belong to the same or different individual.
More information on fisher and marten monitoring by the U.S. Forest Service in California can be found at: https://www.fs.usda.gov/detail/r5/plants-animals/wildlife/?cid=FSEPRD590791