Introduction

Coryi Foundation, Inc. is a non-profit scientific organization studying bobcat (Lynx rufus) population viability in intensely developed landscapes east of the St. Johns River. This is done, in part, by radio-collaring and monitoring bobcats to assess status and document movements through corridors. Based on its findings, the Foundation develops recommendations for the preservation of wildlife corridors and larger habitat areas to which they connect. The end goal of this effort is to insure the long-term persistence of bobcats in intensely developed counties like Brevard. The purpose of this document is to (1) Discuss the effects of the future Port St. John I-95 interchange and potentially associated development as related to local population survival, and (2) Provide landscape management recommendations that minimize these effects. Though the Foundation’s efforts span several coastal counties, this document addresses landscape problems that exist between Mims and Melbourne. This assessment and conservation recommendation is a summary of a more complete and detailed final version that the Foundation will release in January 1999.

Assessment of Landscapes in Brevard County and the Potential Threat to Bobcat Survival

Though the bobcat is not a listed species, there is the potential for its local loss in Brevard County. Development is enveloping and eliminating preferred bobcat habitat. Figure 1 depicts remaining preferred habitats. Out of the 203,858 acres of land that exists between Mims and Melbourne, 50% is developed. Another 25% consists of non-forested wetlands, specifically freshwater marsh, shrub wetlands, and wet prairie - types avoided by bobcats. These types are generally too wet for denning, lack sufficient numbers of preferred prey, and degrade the health of individuals. The bulk of these avoided habitats exist in the St. Johns River floodplain wetland system, 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. These types possess sufficient prey (rabbits and rodent) and suitable denning cover.

The remaining preferred 25% is extremely limited for bobcats. Bobcats are wide-ranging and solitary. Males and females defend territories that average 4800 and 2900 acres, respectively. 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. For bobcats, this equates to about 291,000 acres, far more than all of the land available between Mims and Melbourne.

This limitation of space is significant if development reaches 100% saturation from the St. Johns River floodplain to the Indian River Lagoon at several constricting locations. These locations include Mims, Port St. John, Lake Poinsett, and Lake Washington. The net effect of this saturation could be the creation of one to three small and isolated population cores as depicted in Figure 1. These cores are designated as Titusville, Cocoa, and Viera.

As an example, if the Mims and Lake Washington constrictions were to become fully developed from river to river, the population within would likely be isolated and have available to it only 50,964 acres of preferred habitat. This would limit the number of adults to about 42 to 75 individuals. This population would be far smaller than that required for long-term persistence. If, in addition, the Port St. John and Lake Poinsett constrictions were fully developed, the three cores of Figure 1 would have anywhere from 14 to 30 adults each. [Note: Isolation occurs because, additionally, the St. Johns River floodplain (wide channels and hostile wetlands) effectively prevents movement into the area from the west.]

Under the above isolation scenarios, a number of events will likely occur. Inbreeding rates will increase in the small population(s) 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 otherwise allow a population to adapt to the changes. 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). Furthermore, small populations are more susceptible to epidemics and catastrophies such as fires or hurricanes. Because of isolation, individuals will not be 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 lead to extinction. Thus, bobcats from Melbourne to Mims could disappear.

Furthermore, river to river development at any one of the above constrictions would likely isolate all bobcats east of the St. Johns River from the mainland, from that location north to Jacksonville. This is because the St. Johns River proceeds all the way to Jacksonville where it empties into the Atlantic Ocean. Such could set the stage for future extirpation on a regional scale.

Therefore, to prevent isolation and allow for a large continuous population that is less vulnerable to local extinction, corridors need to be retained, especially at the constrictions indicated in Figure 1. Corridors are linear habitats that facilitate successful movement by adult breeders and dispersing juveniles between population cores. They promote the gene flow required to offset inbreeding effects and help replenish individuals. A corridor that promotes successful movement mostly consists of preferred habitats, possesses minimal impediments like highways, is sufficiently wide, and is the shortest route between cores.

Specific Threat: The Port St. John I-95 Interchange and the Potential for Development

There is a potential threat to movement through the Port St. John constriction. Brevard County is considering developing portions of sections 28 and 27 of Township 23S, Range 35E (Figures 2 and 3). This development is associated with the future I-95 interchange between Port St. John and Canaveral Groves. Habitats that occur in these sections are part of a corridor that skirts the west side of Port St. John and connects the Titusville and Cocoa cores as shown in Figure 2. Our telemetry data suggests that this corridor provides the quickest, shortest and most preferred route that facilitates successful passage around Port St. John, and that it is consistently selected for such movement above the wetlands to the west. Compared with isolated blocks of preferred habitats to the west, this corridor possesses the most continuously forested configuration. The landscape to the west not only lacks forest continuity, but largely consists of unsuitable grass and shrub wetlands that lack forest cover and sufficient prey within their interiors. That landscape discourages passage and drains energy budgets. Bobcats are less likely to penetrate them deeply, let alone make a passage through them. Rather, they possess a greater need for and seek the preferred types located to the east. Animals need the most encouraging route that facilitates passage to a distant population. This is the true function of a corridor. The highly preferred pine flatwoods of section 28 form the beginning of the corridor. Abundant in preferred cover and prey, these flatwoods strongly encourage movement into the corridor.

The interchange project has several aspects that could diminish or destroy the corridor’s ability to foster movement (Figure 3). First, the interchange is massive. The long lengths of the access ramps will add a significant impediment to movement by increasing the rate of road kills, and therefore, decreasing the rate of successful passage. The majority of road kills in the county are those of young males (42%) 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. Young males have the greatest need for corridors since they disperse the farthest and thus, promote the greatest gene flow across a landscape. Juvenile road kills in this corridor will decrease gene flow between the cores. Secondly, the connector road that goes east to Grissom Parkway cuts through a significant portion of preferred habitat, again increasing the rate of road kill of animals accessing the corridor. Depending on the extent, associated commercialization of those lands could prevent immediate passage to the east. Third, the paving of Pine Street from Canaveral Groves to Port St. John is being considered as part of the west connector. Paving would encourage the development of properties in section 28. This is a great threat to the corridor. Telemetry data suggests that development that is more intense than 1 - 2.5 acres per dwelling is unsuitable. Such would likely eliminate forest connectivity and render the corridor useless. Finally, concern expressed by residents regarding routing interstate traffic into the section 33 portion of Pine Street has prompted the consideration of taking a southern extension over to Satellite Boulevard. This too would attract development of lands with the potential for eliminating most of the forest in section 28.

Recommendations for Habitat Conservation

In light of the above, it is strongly recommended that the following occur, as shown in Figure 4:

(1) Shrink the interchange’s size to that as found at State Roads 520 and 50;
(2) Keep the east connector to Grissom Parkway as close to Port St. John as possible;
(3) Limit commercial development to the east connector and only within 200 feet of it;
(4) Keep the Port St. John west access close to Adele Street and Baltimore Avenue on a run that takes it to Golfview Avenue;
(5) Do not provide any access from the west side of the interchange south to Canaveral Groves,
(6) Do not provide any other extension to the west;
(7) Preserve the corridor in section 28 via the implementation of a linear park via Metropolitan Planning Organization funding and a southern  
            expansion of Fay Lake Wilderness Park;
(8) Preserve section 27 via the implementation of the current CARL Project that has been designated for that area and that which may be         
            funded by The Nature Conservancy.
(9) Preserve the TICO Scrub Core via the current CARL Project.

Summary

The bobcat is the last of Florida’s three large carnivores in the area. If bobcats disappear from this area, we will lose yet one more component of our old wild Florida heritage. More importantly, it must be decided if we can afford this loss. 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, overforage 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. 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. 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.

__________________________________

Timothy John Mallow    
Director