The use of off-road vehicles (ORVs) has been a popular recreational activity in Big Cypress National Preserve (BCNP) for many years, and recently more than 2000 individuals per year have received ORV permits (National Park Service 2000). The repeated rutting of marl prairies due to ORV use has caused extensive damage to many areas within the preserve. A management plan has been implemented to mitigate this damage (National Park Service, 2000).

Although the degree of ORV use is well documented in the marl prairies of BCNP, the impact of ORVs on wildlife species is not well known. However, human recreation may result in alterations in behavior and reduce survival (Swarthout and Steid, 2001) or fitness (Parent and Weatherhead, 2000) of wildlife populations.

ORVs in the prairie habitats of BCNP may also have indirect effects on wildlife species. ORV use can impact the vegetation, hydrology, water quality, and soil structure of prairies (National Park Service, 2000). Duever et al. (1981) documented changes in plant species composition and abundance in prairies with high ORV use. The extent to which these environmental changes affect wildlife populations in the prairies of BCNP is poorly understood.

Amphibians and small mammals may be affected directly and indirectly by ORV use in prairies. Further, these animals are particularly suited for this study on the impacts of ORV use on wildlife because they are likely to spend their entire lives completely within or near the same homogenous prairie habitat. Also, they are easily sampled with traps and should occur in great enough abundance to allow the estimation of a variety of population parameters like abundance and survival using mark-recapture analysis.

We will investigate the effects of ORVs on amphibians and small mammals by using mark-recapture techniques to estimate population parameters at sites with varying degrees of ORV use. The two most important population parameters used in this study will be survival and abundance. Our efforts will focus on two groups of species: treefrogs that will be captured in PVC pipe refugia and rodents that will be captured with Sherman live traps.

Grids of 3.5cm PVC pipes will be erected in prairie habitat in BCNP. These pipes are very effective at capturing treefrogs (Boughton et al. 2000). Approximately 50 pipes will be used per site at as many as nine locations. These locations will be classified as having light, moderate, or heavy ORV use. Three replicate sites will be used for each category of ORV use.

PVC pipes will be examined for treefrogs once every two weeks. Captured animals will be carefully removed from the pipe to avoid harm. They will also be identified to species, age, and sex whenever possible, measured snout-to-vent (SVL) and massed using a Pesola^TM hanging scale. Frogs will be marked using a commonly accepted toe-clipping scheme (Donnelly et al. 1994). Toes will be removed quickly with a pair of sharp scissors. No more than two toes per limb will be removed, and the first toe on any limb will not be removed. Scissors and other equipment will be cleaned with alcohol to avoid disease transmission. All methods used have been approved by the American Society of Ichthyologists and Herpetologists and the Society for the Study of Amphibians and Reptiles (http://www.asih.org/pubs/herpcoll.html [site no longer active]). Each frog will be released as soon as possible after capture to minimize stress on the animal.

Mammals will be trapped and handled in a similar manner. Grids of Sherman live traps will be baited with rolled oats to capture rodent species. The grid design will allow us to calculate a density of the animals (Jones et al. 1996). Trapping will be conducted one week each month at each site. Each captured rodent will be identified to species, sex, and approximate age. The body length, tail length, and the mass of each captured animal will also be noted. Finally, each captured rodent will be uniquely marked with an individually numbered ear tag.

In addition to providing important information about ORV impacts on key wildlife species of the prairie habitat, these data will be used with hydrologic data to determine how hydrology affects these species. Specifically, changes in abundance and survival across seasonal hydrological gradients will be observed on sites stratified by ORV use. The presence, abundance, and behavior of the amphibian and small mammal species changes with the transition from dry season to wet season in this habitat will also be examined. Collectively, this information will be valuable for evaluating hydrologic and human-use impacts during Everglades restoration.

REFERENCES

Boughton, R. G., J., Staiger, and R. Franz, 2000, Use of PVC pipe refugia as a sampling technique for hylid treefrogs. American Midland Naturalist 144:168-177.

Donnelly, M. A., C. Guyer, J. E. Juterbock, and R. A. Alford, 1994, Techniques for marking amphibians. in W. R. Heyer, M. A. Donnelly, R. W. McDiarmid, L. C. Hayek, and M. S. Foster, editors. Measuring and monitoring biological diversity: standard methods for amphibians. Smithsonian Institution Press, Washington, D.C.

Duever, M. J., J. E. Carlson, and L. A. Riopelle, 1981, Off-road vehicles and their impacts in the Big Cypress National Preserve. National Audubon Society, Ecosystem Research Unit.

Jones, C., W. J. McShea, M. J. Conroy, and T. H. Kunz, 1996, Capturing mammals. Pages 115-155 in D. E. Wilson, F. R. Cole, J. D. Nichols, R. Rasanayagam, and M. S. Foster, editors. Measuring and monitoring biological diversity: standard methods for mammals. Smithsonian Institution Press, Washington D.C.

National Park Service, 2000, Final recreational off-road vehicle management plan supplemental environmental impact statement. U.S. National Park Service, Big Cypress National Preserve, Ochopee, FL, 603 pp.

Parent, C., and P. J. Weatherhead, 2000, Behavioral and life history responses of eastern massasauga rattlesnakes (Sistrurus catenatus catenatus) to human disturbance. Oecologia 125:170-178.

Swarthout, E. C., and R. J. Steidl, 2001, Flush responses of Mexican spotted owls to recreationists. Journal of Wildlife Management 65:312-317.

White, G. C., and K. P. Burnham, 1999, Program MARK: survival estimation from populations of marked animals. Bird Study 46 supplement: 120-138.

Contact: J. Hardin Waddle, Florida Cooperative Fish and Wildlife Research Unit, Box 110430, University of Florida, Gainesville, FL 32611, Phone: 353-392-2861, hardin_waddle@usgs.gov

(This abstract was taken from the Greater Everglades Ecosystem Restoration (GEER) Open File Report 03-54)

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