Florida is growing rapidly in terms of numbers of people and new developments. With its population increasing at an exponential rate, it could be predicted that east central Florida is soon to attain the same extent and degree of development as Los Angeles, California. Unless proactive steps are aggressively taken, most of the remaining upland habitats could disappear. Brevard County is experiencing such a threat between Mims and Melbourne, between the St. Johns River and the Indian River Lagoon. Habitat loss in this area is trending to a complete depletion of functional upland habitats and avenues of travel for many terrestrial species. This is significant because this long and narrowly shaped area is the only link for gene flow between the northern and southern areas of the county. The barrier Islands are no longer functional for movement on this scale - saturating development from Port Canaveral to Indiatlantic Beach has already occurred. Thus, the mainland of Brevard carries a heavy burden when it comes to regional gene flow east of the St. Johns River.

Though the bobcat is not a listed species, there is the potential for its local loss in mainland Brevard County due to aggressive and enveloping development. Out of the 203,858 acres of land that exists between Mims and Melbourne, 50% is developed. Another 25% consist of non-forested wetlands, specifically freshwater marsh, shrub wetlands, and wet prairie - types avoided by bobcats (Wassmer et al. 1988, Maehr 1997, Mallow and Klinkowski 2000, Mallow 1999, Mallow 1998). These types are generally too wet for denning, lack sufficient numbers of preferred prey, and degrade the health of individuals (Mallow 1999). The bulk of these avoided habitats exist in the St. Johns River flood plain, toward which development is pushing and which is quickly becoming the last natural area of appreciable size. The remaining 25% (50,964 acres) constitutes the only amount available as preferred bobcat habitat and consists of wetland forests and development-vulnerable upland types. These include pine flatwoods, upland hardwoods, upland brush stages, and mixed forest wetland (Mallow and Klinkowski 2000, Mallow 1999, Mallow 1998, Griffith and Fendley 1986). These types possess sufficient prey (rabbits and rodent) and suitable denning cover (Golley et al. 1965, Maehr and Brady 1986).

The remaining preferred 25% is extremely limited for bobcats because they are wide-ranging and solitary. Males and females defend territories that average 4800 and 2900 acres, respectively (Wassmer et al. 1988, Mallow 1999). Both sexes do not allow other adults of the same sex to occupy their ranges. These territory sizes and this social structure dictate that populations require extensive tracts of land. In order to be free of the extinction-yielding effects associated with small populations, a population requires at least 200 adults (Cox et al. 1994). This equates to about 291,000 acres, far more than all the land available between Mims and Melbourne.

This limitation of space is significant if development reaches 100% saturation from the St. Johns River flood plain to the Indian River Lagoon at locations such as Port St. John and Lake Poinsett. The net effect could be the creation of an isolated population in the Cocoa area depicted in the map of Figure 1. This population would be far smaller than that required for long-term persistence (Cox et al. 1994) since it would have no more than 30 adults, given the size of the area. (There are other portions in the county where such isolation is in progress, but for the purpose of this report, I am focusing on the Cocoa area.)

Under the above isolation scenario, a number of events will likely occur. Inbreeding rates will increase in the small population and lead to a reduction in genetic diversity. Loss of genetic diversity can limit a population’s ability to respond to changes in the environment. This is because some of the loss in variation could be due to a loss of genes that would otherwise allow a population to adapt to the changes (Franklin 1980, Allendorf and Leary 1986). Inbreeding depression can allow the expression of harmful genes that can debilitate offspring. These effects include reduced immunity to diseases, lowered reproductive success, and the onset of physical impairments (some of which are fatal) (Ralls et al. 1988). These effects have already been documented in other species whose numbers have been reduced either by natural isolation, persecution, and/or habitat loss (Packer et al. 1991, Packer 1992, O’Brien and Evermann 1988, Roelke 1988 and 1989). Furthermore, small populations are more susceptible to epidemics and catastrophies such as fires or hurricanes. Because of isolation, individuals are not able to move into an isolate to replenish losses that arise from mortalities. Additionally, the gene flow that is needed to offset the effects of inbreeding will not occur. These events typically spiral into an extinction vortex in which the factors that effect a small population tend to drive its size progressively lower (Gilpin and Soule 1986). The end result is extinction. Thus, if the landscapes of Brevard County fall victim to the aforementioned scenario, bobcats from Melbourne to Mims could become locally extinct, with areas like Cocoa being the first to experience the extinction process.

It must be mentioned that the above isolation scenario is compounded by another factor: urban sprawl that is pushing westward to the flood plain as the developments of the Cocoa area increase, as they are throughout the rest of the county. Sprawl itself will create isolated pockets. Worse, it will impose a less forgiving situation by effectively eliminating and fragmenting large blocks of upland habitats within the Cocoa area that are better left undisturbed. Habitat loss associated with the westward sprawl will force remnant individuals to retreat to the wetter flood plain areas to the west. Forest animals (such as bobcats) can make little use of those areas simply because they are not well adapted to a vast marsh landscape. Thus, what we are ultimately addressing here is not only the potential loss of the bobcat from much of central portion of the county, but the loss of other species that are as dependent on forested or upland communities.

Habitat loss in the Cocoa area is not only reducing carrying capacities and leading to isolation. Fragmentation of the otherwise intact habitat blocks resulting from the increase in the number of roadways that bisect functional habitats and the subsequent increase in vehicular traffic are putting more animals at risk of being killed by automobiles. This cause of mortality may be the leading cause of death for individuals in the county and may significantly weaken demographic stability. From 1993 to 1998, this Foundation documented 28 road kills (mean of 5.6 per year) between Mims and Melbourne. It is estimated that there is a 13.3 % annual mortality rate due to a road death portion alone. Surely, more road deaths are occurring than documented. What is alarming is that the majority of road kills in the county are those of young males (41%) that are in the process of dispersing from a birth range. Young females, adult males and adult females account for 9, 25, and 25%, respectively (Mallow, unpublished data). This is significant because young males disperse the farthest (Griffith and Fendley 1986) and hence, promote the greatest gene flow across a landscape. Thus, road kills decrease gene flow as well as contribute to a weakening of demographic stability.

As shown in Figure 1, the Cocoa area consists of a large block of functional habitat as shown by the dark shaded areas. This area can be considered what is referred to as a ‘core’ area in that it provides residence for a moderate number of bobcats. It is estimated that as many as 30 bobcats reside within the core. Figure 1 also shows the home ranges of several bobcats, as documented via Foundation radio-telemetry monitoring. Such gives one an idea of relative numbers compared to the available amount of suitable habitat. I.e., there is not much available space in the Cocoa core.

There is great variation in apparent home range sizes among the 4 cats. The largest range (B035) is 6570 acres in size, which is 25% larger than the average for a male. Based on this figure and the state average (4800 acres), the adult males in the area are using a lot of space compared to what’s available. This fact alone demonstrates the need to protect the habitats of the Cocoa core from further destruction. Also, the location of his range suggests he used an appreciable amount of non-preferred habitat. On the contrary! He used the preferred habitats that laced the developed matrix in a connective way as links across the landscape of his territory; for indeed he was always located in forested habitats and not developed areas. The ranges of B056 and B057 are smaller for a couple reasons. In the case of B057, he had been shot within a few months of capture and therefore his range size is an underestimate since insufficient data points had been collected. As for B056, it is suspected he was preying on domestic animals in the Canaveral Groves subdivision (typical behavior for juvenile males) and therefore was not exhibiting a normal size range typical for wide-ranging predators that normally have to travel wide in order to conserve natural prey resources. With regards to B060, this cat was a 6 month old kitten that was still dependent on his mother. Thus, his travels were mostly confined to areas around den sites. It is encouraging and interesting to note that he and his mother were occupying habitats nearly as far east as US1. Developments increase dramatically as US1 is approached from the west. Yet, pockets of undisturbed land remain.

The fact that there is a lack of radio-collared representation in the center part of the core does not nullify its use by bobcats. Documented road kills throughout core attest to that. What’s being demonstrated in this map is the fact that there is limited space compared to relative bobcat density, based on home range sizes. More importantly, the landscape is more than less isolated (i.e., pinch-off points of Port St. John to the north and Rockledge to the south). Thus, gene flow in and out of the core is somewhat impeded. All that being said, the residences of the core need all remaining upland and forested space. Any further reduction of habitat can significantly weaken demographic stability in the core.

To allow for a large continuous population that is less vulnerable to local extinction and provide a measure of safeguard for biodiversity, core habitats (the large blocks of habitat such as that which exists within the Cocoa core) need to be protected – that is, kept from further reduction in size. The Cocoa core is extremely important since it serves as a breeding ground and ‘source’ population from which individuals can move to outlying areas in the county. It goes without saying that Brevard County is rapidly losing these types of "berthy" habitats. Because further reduction in habitat in the Cocoa core can weaken demographic stability, it can also diminish the core’s value to the rest of the county as a source of genetic material. For this reason, development trends need to decrease to prevent further loss of habitats.

Also, corridors need to be retained in the Cocoa area – within the core and also those that lead to areas to the north and south of the core. Corridors facilitate successful movement between population cores by adult breeders and dispersing juveniles (I.e., movement between the Cocoa core and the cores existing to the north of Port St. John and south of Rockledge). They promote the gene flow required to offset inbreeding effects and help replenish individuals within other cores. Corridors within a core provide animals with routes that allow them to move between developed areas in order to make passage to various habitat blocks within the core. All four males in the Cocoa core made use of these intra-core corridors in this way. Animals will favor a corridor that possesses the plant communities they prefer (Noss and Cooperider 1994). For the bobcat such habitats are invariably forested.

Corridors are useless if there are insufficient core areas in which animals can live and reproduce. Hence, the need to protect the Cocoa core from further habitat loss. Obviously, core tracts are the units on which corridors terminate. Since interconnecting core lands via corridors is intended to virtually assimilate a single large virtual conservation area that meets the genetic and life history needs of wildlife, habitat berthiness and robustness are the paramount needs in the Cocoa area and in the county at large.

Conclusion and Implications to Biodiversity

The bobcat is the last of Florida’s three large carnivores (Maehr 1997) in the area. The other two (now absent) large carnivores are the Florida panther (Felis concolor coryi) and black bear (Ursus americanus floridanus). If bobcats disappear from this area, it will lose yet one more component of its old wild Florida heritage. More importantly, it must be decided if the loss can be afforded. The bobcat is a keystone species. This means that its presence determines what other species exist in the food web, as well as their abundances. 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. And because the bobcat is all that remains of the three large carnivores in the area, it could be considered the last best defense in terrestrial prey regulation. We have already witnessed the cascading effects of predator removal. When Florida panthers and red wolves (Canis rufus) were extirpated from the barrier islands, raccoon (Procyon lotor) populations increased. So significant was this increase, that the subsequent increase of predation by raccoons on sea turtle eggs is likely a major reason for sea turtle endangerment (Breininger et al. 1994). One cannot help but speculate what will happen if the bobcat disappears. That is, what kind of animal community structure erosion will follow.

The bobcat is also an umbrella species. Because bobcats need lots of forested land, efforts to maintain them automatically umbrella the preservation of the many other species that need less land, without duplicated cost. This aspect has far reaching implications for biodiversity. Except for the Florida panther and black bear, the bobcat is the only terrestrial animal that collectively spans the largest area and makes use of the greatest number of different habitat types (Mallow and Kharbanda 1998). Because of this, the bobcat is an excellent model for large-scale biodiversity and barometer of ecoregion health. That it is often referred to as a focal species has its roots in just this very thing. Its presence implies true wilderness in a landscape. If a population can survive in the long term, then it is because there is a vast amount of wilderness that likely encompasses a full spectra of habitats – habitats that benefit an extremely large number of different species (Mallow and Kharbanda 1998). Thus, when we speak of bobcat conservation, we are really speaking of large-scale biodiversity conservation. And when we speak of protection of the Cocoa core habitats, we are also speaking of the same.

The Cocoa core sits at the apex of large-scale biodiversity in the county. As one of the largest core areas in Brevard County, it serves as a valuable natural resource and as a source of genetic material for outlying areas. As part of the county-long link east of the St. Johns River, it serves as an important node in the hierarchy of large-scale movement - a vital ‘way station’ for animals that are en route. Every effort needs to be made to minimize further loss of habitats that are not only important for the bobcat, but for other forest species. Any further destruction of the core’s forest communities by development will weaken the core’s vitality as a resource that is needed for a self-sustaining bobcat population. And what will follow will be a further degradation of biodiversity, beyond which recovery eventually becomes impossible.

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