Comparing density estimates of panthers on public and private lands

Trail camera.

Our state mammal of Florida is also one of our most elusive – the Florida panther (Puma concolor). Rarely seen, the Florida panther is listed as Endangered under the Endangered Species Act. Considering how fragile, due to small size and geographic footprint, the panther population still is in Florida, accurate data are needed on population density estimates. Deriving population estimates or density for panthers is notoriously difficult due to their reclusive nature and their wide-ranging movements. In 2014, FWC initiated a previously-designed project to assess whether data collected on panthers via trail cameras could be utilized within a spatial mark-resight model framework to determine the density of panthers at a study sight.

Through the 19th and early 20th Century, the Florida panther was hunted extensively throughout Florida, with a dwindling population of around 30 panthers in the early 1980s. Severe inbreeding resulted in many health and physical problems for the panthers during this time. A genetic restoration project initiated in 1995 was deemed successful in improving genetic health and vigor of the panther population. From only around 30 panthers in the 1980s to an estimated population of 120-230 currently, managers and conservationists remain cautiously optimistic. Florida panthers are still a delicate population, however, and human-related mortalities like car-strikes and pressure from shrinking habitat, still occur too frequently.

Assessing the density of panthers across a range of habitats on both public and private lands has the potential to inform managers on how to better manage habitat. Knowing how many panthers are living in any given area allows managers to assess progress on recovery criteria for this endangered animal. Although Florida panthers have been sighted throughout peninsular Florida – particularly males – this study focused on the breeding population in areas of Collier and Hendry counties in southwest Florida. If we can better manage the landscapes these panthers call home, and improve prospects for panthers living in these areas, we are helping with the recovery of this graceful and powerful predator. Deriving a methodology that is standardized and repeatable will allow researchers to continually reassess how the panther population is faring over time.

Over several years, FWC researchers captured and marked Florida panthers with unique radiocollars and ear tags on three different study areas during the winter, then deployed 50 study-cameras each across an approximately 162 square kilometer study grid in the spring. The cameras were deployed for various time periods, but a minimum of five months of data were used for the analysis at each study area. The photographs from the cameras were then analyzed by identifying marked individuals (collared, ear tags and unique traits) verses  unmarked/unknown Florida panthers. Using these data, researchers are then able to derive estimates of population density.


 

The lead FWC researchers with this project are Dave Onorato and Marc Criffield, although other researchers worked on this project as well. FWC researchers discovered that while this methodology will allow managers to derive estimates of panther density at study sites with acceptable levels of precision, it may not allow them to extrapolate said information across the breeding range to obtain a range-wide population estimate for panthers. The question is something researchers will continue to assess with quantitative ecologists since range-wide estimates are often necessary to monitor recovery and desired by the public for endangered animals. “It was interesting for us to watch our collared panthers through the chronological photographs.” Criffield said, “Most panthers we collar we rarely see again and usually just monitor their location with the radiocollars.”

While the cameras captured high-quality images of several panthers, sifting through the data proved time-consuming for the researchers. “Collecting and analyzing data for this project took considerable effort.” Onorato said, “On the private ranch alone, we accumulated over 1 million photographs, but only a small percentage of which were actual panthers.”

This project was funded primarily by the Florida Panther Research and Management Trust Fund, which are derived from donations associated with the purchase of “Protect the Panther” Florida license plates. The FWC programs that were involved with this project were the Fish and Wildlife Research Institute’s Wildlife Research program, and HSC’s Imperiled Species Management. There were several key partners associated with this program, including a mix of state and federal land managers within FWC, DEP, Florida Department of Forestry, US Fish and Wildlife Service and the National Park Service. Researchers also collaborated with private landowners to utilize this study design on large parcels of private land.

  • An uncollared, male Florida panther captured on a trail camera on April 15, 2014 in northern Big Cypress National Preserve.

  • Female Florida panther FP226 captured on a trail camera on May 28, 2014 in northern Big Cypress National Preserve.

  • Female Florida panther FP226 captured on a trail camera on June 5, 2014 in northern Big Cypress National Preserve.

  • An uncollared, male Florida panther captured on a trail camera on July 23, 2014 in northern Big Cypress National Preserve.

  • Female Florida panther FP199 and her two kittens captured on a trail camera on August 4, 2014 in northern Big Cypress National Preserve.

  • Florida panther FP216 was captured on a trail camera on November 9, 2014 and identified even though he had dropped his radiocollar because multiple making techniques were used including unique ear tags.

  • Uncollared Florida panther “captured” on a trail camera traversing though high water on September 22, 2017, 12 days after the landfall of Hurricane Irma.