Bobcats, Corridors, and the Eastern Florida Flatwoods Ecoregion
The Regional Effects of Habitat Loss in Brevard County
By Tim Mallow
What is additionally disconcerting is the sequence of events leading up to these deaths. Making use of landscapes that have been subjected to intense habitat loss as a result of development, some adults do manage to defend severely fragmented or smaller than typical home ranges and find each other to mate. Within a year of birth, juveniles will disperse in search of space in which to establish their adult ranges. However, vacant ranges are rare in the severely fragmented landscape.
As a result, juveniles will range widely, exploring hostile terrain - often being harassed by larger and more experienced resident adults that occupy the landscape at or near carrying capacity, or being shot at as a nuisance. These factors force these younger cats into areas that are used less by bobcats, but areas that are also less suitable - the watershed marshes. There they frequently travel along a highway because it is one of the few available dry areas that possess appreciable cover - the shrubby vegetation adjacent the road. Unwarily, they wander onto the paved road where they are frequently killed by an automobile.
That the watershed is a cure-all for the needs of wildlife is a notion that fails to consider the life history traits and ecology of the bobcat. Bobcats prefer forested habitats. Marshes are not optimal habitat. They generally lack sufficient cover and are frequently too wet. Furthermore, bobcats are most fit when they have access to abundant rabbits and cotton rats. Though the marshes contain these prey items, they are more abundant in drier habitats.
Unfortunately, uplands in Brevard County, like anywhere else, are the targets of development. Brevard County is one of the fastest growing counties in Florida. Close proximity to many attractions and industry make it an idea area for growth. The Kennedy Space Center, high technology industries, seaside attractions, and nearby Orlando collectively act to increase residential and commercial developments in the county. As a result, Brevard County has experienced intensive habitat loss resulting in the loss of a significant amount of suitable bobcat habitat as shown in Figure 1 below.
Should the remaining uplands be developed, bobcat numbers will further decline and those remaining will be forced to exclusively occupy the less suitable habitats in the watershed. As these habitats are unsuitable for bobcats, population viability will probably decline. This is because poor quality habitats tend to decrease reproductive success and general individual health.
This situation presents a significant problem on a regional scale. Brevard County probably acts as a vital link for terrestrial wildlife populations to the north and may be considered the only avenue for gene flow into that area. That area is the northern part of the Eastern Florida Flatwoods Ecoregion - the area defined by the St. Johns River, the intracoastal waterway, Jacksonville, and Brevard County as shown on Figure 2 below.
Brevard County could be viewed as the only link into that area because the St. Johns floodplain probably acts as a virtual barrier to any significant immigration from the west. Thus, that block is vulnerable to genetic isolation. Should natural areas in Brevard County be developed to the extent that wide-ranging species such as the bobcat are no longer able to make a passage through the county from south to north, then gene flow could cease to occur from areas south of the county into that northern habitat block.
Though its natural areas are currently sufficiently large and continuous to promote bobcat population viability, future development in that northern area will likely fragment and shrink those populations. As a result, populations could genetically drift toward monomorphism - the loss of genetic variability. This is because population reduction can lead to an increase in the rates of inbreeding - matings between individuals of similar genetic make-up. A lack of genetic variation can lead to an expression of lethal recessive genes and a loss of genes important for survival and adaptation to changing environmental conditions. A host of biomedical problems can subsequently occur: a decrease in reproduction, an increase in physiologic impairments (some are fatal), and a decrease in immunity to diseases. These anomalies tend to weaken a population's demographic stability. Numbers decline and age and sex structures are skewed. The process tends to feed on itself and contributes towards increased biomedical problems and further population reduction. The end result is that bobcats in those eastern counties could eventually disappear in an extinction vortex associated with small populations.
The bobcat is the only large Florida carnivore remaining at population status in Brevard County. If bobcats disappear from this area, it will lose yet one more component of the food web and its old wild Florida heritage. It must be decided if this can be afforded. The bobcat is a keystone species and its absence as a top predator can induce erosion in animal community stability. This means that its presence determines what other species exist in the food web, as well as their abundance's. Its absence as a keystone predator can cause prey populations (rabbit and rodent) to increase, over-forage and deplete their own food sources.
This food depletion can increase competition between species that use the same foods. Some species may dominate the dwindling food supply and cause others to disappear.
Thus, bobcats help maintain natural balance and their loss can induce the loss of other species. Such is the nature of cascading degradable effects associated with the disappearance of top predators from the biosphere. This is a theme that has already occurred in Florida. With the extirpation of the panther, red wolf, and black bear from east central Florida, raccoons have increased in numbers and so has their rate of depredation on sea turtle eggs. This increased depredation is likely one of the causes that sea turtles are now endangered. One can easily guess what will happen to rabbit and rat populations when the bobcat disappears and can only imagine what ecological problems will follow. The bobcat is also an umbrella species. Because bobcats require lots of forested land, efforts to maintain them automatically umbrella the preservation of the many other species that need less land, without duplicated cost.
Finally, people benefit from their presence. As a symbol of old Florida that enhances the aesthetic quality of an area, its exciting to see a bobcat and habitat protection provides natural areas for people to enjoy and travel back in time. To prevent local extinction of the bobcat and these cascading effects, Coryi Foundation, Inc. is conducting radio-collar and biomedical research on bobcats to determine how habitat loss and fragmentation have effected bobcat populations in Brevard County and the ecoregion. With the use of radio-telemetry, the Foundation is also identifying the corridors and core tracts they use.
The Foundation will use this information to develop a corridor-core reserve network habitat conservation plan that can be used to promote ecoregion-wide connectivity. This connectivity will insure that freedom of movement is retained throughout Brevard County and the ecoregion so that genetic links stay open. It will insure that a metapopulation network of population cores exist, possess sufficient protected habitat, and are connected with each other via corridors. These measures will insure genetic variability and a viable persistence of the bobcat and its community throughout the ecoregion. The plan will target corridor and core lands that are deemed essential for long term persistence as priorities for conservation. The plan will be used as a vehicle to encourage organizations involved with land acquisition and habitat protection to work towards preserving the targeted lands.
Related Material:
Bobcat Metapopulation Research and Conservation Project Summary of Goals
Bobcat Population Dynamics in Fragmented Landscapes Research
The Potential Threats to Bobcat Population Viability in Brevard County
Figure 1. Map of Current Suitable Bobcat Habitat in Brevard County.
The map reveals that north-south connectivity in Brevard County is minimal at best.
BACK TO MAIN TEXT
IMPORTANT FACTS TO KEEP IN MIND WHEN VIEWING THE MAP:
This map merely shows what currently exists as suitable bobcat habitat. It does not provide information about how bobcats are actually using the landscape. Because of this, the map cannot be used by itself to develop habitat conservation plans. What is needed is real-time scientific evidence of how bobcats are actually using the landscape. This evidence is currently being obtained through the research being conducted by Coryi Foundation, Inc.
A Habitat Conservation Plan for the landscape depicted in the map below is of little value without direct evidence of what locally works for animals in terms of landscape patterns. Landscape patterns vary from locale to locale. Patterns strongly influence habitat selection. Even if a parcel of land contains preferred habitats, it may never be used by a certain species if it does not fit into the landscape in a pattern that the species favors. What looks good on a map that merely depicts all preferred habitats does not necessarily reflect how animals will actually use the landscape. Furthermore, models, extrapolations from literature, etc., need to be tempered with local field-derived research data because they are either largely theoretical or applicable to other landscapes or populations. The direct evidence can only be obtained from radio-telemetry research. Likewise, reserve network design factors in a habitat conservation plan can only be obtained from radio-telemetry. These factors include the appropriate size and shape of corridors, the range of tolerated spatial habitat heterogeneity, the effects of roads and other anthropogenic structures, etc. As such, a habitat conservation plan and any simple map of preferred habitats in this case is generally useless until the scientific evidence obtained from radio-telemetry produces the real data on how animals actually use the particular landscape. This evidence is currently being obtained through the research being conducted by Coryi Foundation, Inc.
Coryi Foundation, Inc. will be developing the Habitat Conservation Plan based on the research findings and other criteria.
GREEN - SUITABLE HABITATS - upland forests, wetland forests (nongrass stages of the sere), limited agriculture, etc.
WHITE - UNSUITABLE HABITATS - urban development, agriculture, barren lands, non-forested wetlands.
BLUE - WATER.
Figure 2. The Eastern Florida Flatwoods Ecoregion.
BACK TO MAIN TEXT
Great information. I will check out the rest of your blog.lion fighting dog
ReplyDelete