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 5 largest subpopulations in Florida of just under 3,000 bears was done in 2002 and, therefore, the FWC conducted a 2 year study in 2014-2015 to 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) (i.e., 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 (e.g., 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, lack distinguishing characteristics, 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 June and July, a period of time when bears are normally active, 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 in 2014 and the Eglin, Apalachicola, and Big Cypress subpopulations in 2015.

RESULTS

Our results indicate bear numbers have increased considerably since 2002, having more than doubled in the North BMU and increasing significantly in the Eglin, Apalachicola, and Big Cypress subpopulations.

Average number of Florida black bears in five subpopulations from 2002 and 2014-2015 estimates.  Analysis is continuing and estimates may change slightly.
 

Subpopulation

2002 estimate

2014-2015 estimate1

 Change

Eglin

82

140

70%

Apalachicola

568

1,080

89%

Osceola

256

620

114%

Ocala/St Johns

1,025

1,230

27%

Big Cypress

697

1,150

65%

Totals2

2,628

4,220

60%

1Totals rounded to nearest 10. 2Does not include approximately 30 bears in the Big Bend region or the approximately 100 bears in Glades and Highlands counties.

 

Much of the increase we documented occurred from range expansion by bears since the 2002 estimate.  Bears are now abundant or common in approximately 45% of Florida which represents a significant increase in range since 1993 when FWC estimated bears occupied 17% of Florida.  The new range map can be seen below, with a detailed description here Adobe PDF.

BearRange2016.jpg 

Bears are usually found where food, cover and security are available and some parts of their habitat provides more food (is higher quality) than other places and so bears do not occur evenly across the landscape.  Maps from 2014 reveal where the model estimates bears are more (red to orange colors) and less numerous (yellow to green colors) in the Osceola and Ocala/St Johns subpopulations.  Further analysis of 2015 data will allow us to map bear density in the Eglin, Apalachicola, and Big Cypress subpopulations later this year.    

You can read or download the full technical reports online:
2014 Report PDF Adobe PDF (1MB)

2015 Report PDF Adobe PDF (1.4MB)

 

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). 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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