Read summaries from the Florida black bear abundance study.

Florida Black Bear Abundance Study

INTRODUCTION

 The Florida black bear (Ursus americanus floridanus) historically occurred throughout the state but was reduced to an estimated 300–500 bears in the 1970s due to loss of habitat and unregulated hunting.  As a result, the Florida Fish and Wildlife Conservation Commission (FWC) classified the black bear as a Threatened Species throughout most counties in 1974. 

In 2011, FWC conducted an evaluation of species listed as State Threatened using criteria developed by the International Union for Conservation of Nature (IUCN).  The Florida black bear was found not to be at high risk of extinction and was therefore recommended to be removed from the state list.  As part of the removal process, the Florida Black Bear Management Plan Adobe PDF was developed and approved. The goal of the plan is to manage the black bear so that it never meets the criteria of a threatened species again. One of the high ranking priority needs in the Management Plan is to estimate bear numbers every 10 years.  The last estimate of bear numbers for the five largest subpopulations in Florida of just under 3,000 bears was done in 2002, and therefore, the FWC began a two-year study in 2014 to again estimate bear numbers.

HOW WE ESTIMATED BEAR NUMBERS

Today, bear range in Florida is comprised of seven distinct subpopulations each assigned to its own Bear Management Unit (BMU): Apalachicola in the East Panhandle BMU; Eglin in the West Panhandle BMU; Osceola in the North BMU; Ocala/St. Johns in the Central BMU; Chassahowitzka in the Big Bend BMU; Highlands/Glades in the South Central BMU; and Big Cypress in the South BMU.  Some of these subpopulations are small (for example, Chassahowitzka) and all are impacted to various degrees by habitat fragmentation which restricts movements and genetic interchange.  Some subpopulations seem to be increasing.  A key component of sound conservation and management of bears is knowing how many bears live in each subpopulation.  However, bears are generally secretive, live in dense vegetation, exist at low densities, and wander over large areas; characteristics that make a direct count of bears impossible.  Instead, the FWC used a common method to statistically but indirectly estimate bear numbers known as mark-recapture.  To illustrate this method, imagine a large bucket of red marbles for which we need to estimate the number.  The only marbles visible are the ones on the surface so a direct count is not possible. However, if we removed – say 100 marbles, marked them with white paint, put them all back in the bucket and shook up the bucket we could remove a second sample of marbles, some of which would likely be white.  By observing the proportion of white (marked) marbles in the second sample we could estimate the proportion of marked marbles (100) in the bucket to unmarked marbles in the bucket.  The estimate may be off the true number somewhat on the first attempt,  but if repeated enough times, the average estimate will get closer and closer to the actual number.  This, in a nutshell, is how we estimated bear numbers. We attracted bears to a small barbed wire enclosure called a hair snare, obtained tufts of hair left behind, and analyzed the DNA in the hair follicles to identify individual bears.  These were our “marked” bears. We repeated this process six times in 2014 and, with the help of some sophisticated population models that took into account the probability that a bear was detected, bear home range characteristics, behavioral differences among bears, and habitat types surrounding the hair snare, we generated population and density estimates for bears in the Osceola and Ocala/St. Johns subpopulations.

RESULTS

Our results indicate bear numbers have increased considerably since 2002, having more than doubled in the North BMU and increasing by a third in the Central Bear Management Unit.

The average number of bears in the Osceola and Ocala/St Johns subpopulations from 2002 and 2014 estimates:


Abundance Estimate

Average number of bears in 2002

Average
number of bears in 2014


% Increase

Osceola

256

549

114%

Ocala/St. Johns

1025

1297

27%


The increase in Osceola was due, in part, to the wider area surveyed in 2014 compared to 2002 and the model’s use of percent forest cover to estimate numbers. Much of the area surveyed is covered in forest.

It seems likely that the apparent increase in the Ocala/St. Johns subpopulation was influenced by the timing of the 2002 estimate because it was only a few years after the 1998 wildfires that destroyed so much bear habitat in Volusia and Flagler counties. Sixteen years after the fire, vegetative conditions are much better and bears have responded.

Bears are usually found where food, cover and security are available and some parts of their habitat provide more food (are higher quality) than other places and so bears do not occur evenly across the landscape.  The two maps reveal where the model estimates bears are more (tan to grey colors) and less numerous (yellow to green colors).

Fieldwork to estimate bear numbers in the East and West Panhandle Bear Management Units began in May 2015, and we expect to have those estimates completed by July 2016. 

You can read the full technical report for the 2014 results here Adobe PDF

 

Bear density map, caption below

Estimates of bear density in the Osceola and Ocala/St. Johns bear subpopulations, measured in bears per square kilometer (about 247 acres); black squares represent hair snares. Note that the scale of bear density on this map is the same for both study areas, 0.02 bears per km2 for each shade of color. This standardization allows comparisons between subpopulations and shows the higher bear densities that occur in the Ocala. St. Johns subpopulation.

 

 



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