Mapping Florida Bear Range

In the most recent range maps, FWC biologists used objective, data-driven methods to map Florida black bear range statewide and compared it to range from the prior decade. They used multiple data sources and subsampling techniques to reduce potential biases and sophisticated spatial analyses to draw range boundaries and differentiate several levels of occurrence. The methods and results were published in Scheick, B. K., M. A. Barrett, and D. Doran-Myers. 2023. Change in black bear range and distribution in Florida using two decadal datasets from 2001–2020. Journal of Wildlife Management 87(4):e22394.

To summarize that publication, bear researchers first collected location data from multiple sources across the state in a 10-year period (2011-2020). Each data point included a known bear location and date. Datasets included:

FWC Bear Management Data
1. Reported bear mortalities (e.g., vehicle strikes)
2. Bear-related incidents (e.g., human-bear conflicts, injured bears)
3. Orphaned cubs

FWC Bear Research Data
Genetic samples collected for mark-recapture abundance studies

Opportunistic Observations
1. Sightings by wildlife professionals (e.g., FWC staff, reported by other agencies to the Florida Natural Areas Inventory)
2. Sightings by members of the public (e.g., FWC Bear Sightings Registry, iNaturalist)

Researchers inspected the data to remove duplicates or errors as well as to reduce biases (subsampling). They then plot occurrences and conducted spatial analyses. To define areas of frequent and common bear range, they used a “kernel density estimator” (KDE) which identifies areas of highest bear occurrence based on the number and distribution of bear occurrences. The narrower area estimated from the 90% KDE defined the frequent occurrence range and the 97.5% KDE defined the common occurrence range. The occupied range is the common occurrence without the frequent occurrence cut out.

To define occasional bear range, they used a “concave hull”, which outlines areas of general bear occurrence coarsely. The hull included all KDE areas, so the range extent used in the publication is equal to the frequent, common and occasional areas combined. The remainder of Florida not included within the frequent, common, or occasional range delineations was considered rare bear range.

FWC research methods produced detailed, reproducible, and reliable bear range maps to inform the FWC Bear Management Program, Florida residents, and all interested stakeholders. Maps are both visually and quantitatively comparable over time so that trends in range extent can be identified.