Graduation Year

2004

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Biology

Major Professor

Peter Stiling, Ph.D.

Committee Member

Gary Huxel, Ph.D.

Committee Member

Gordon Fox, Ph.D.

Committee Member

Phillip Frank, Ph.D.

Keywords

Browse, Regeneration, Fire, Urban, Odocoileus virginianus clavium

Abstract

The Key deer (Odocoileus virginianus clavium) population has increased from less than 80 individuals in the 1950s to approximately 700 by 2000. Over two-thirds of the Key deer population resides on two islands out of a potential 26 islands within their range. The skewed distribution resulted in high deer densities on Big Pine, No Name, and Big Munson keys. The objective of the study was to evaluate the effects of Key deer herbivory in mangrove, buttonwood, hammock and pineland habitats between islands with low, medium, and high densities of deer. Host-plant choice trials were conducted to determine Key deer selection among plant species. Subsequent analyses on vegetation were then compared by deer preference categories: preferred and nonpreferred plant species. Vegetation quadrats, deer exclosures,nursery plant species, and baseline vegetation data were used to examine the effects of Key deer browsing on plant communities. For most analyses, browsing impacts were not evident for the entire plant assemblage (e.g. all plant species combined, diversity, species richness etc.), but were noticeable when plant species were dichotomized by deer preference. The strongest negative impacts of browsing were seen for highly preferred plant species, such as Bursera simaruba, Erithalis fruticosa, Bumelia celastrina, Rhizophora mangle, Jacquinia keyensis, and Guapira discolor, which all had very low densities on high deer density islands. Some nonpreferred species exhibited a positive relationship with high deer densities, such as Eugenia spp., Piscidia piscipula, and Coccoloba diversifolia among others. Urbanization also influenced Key deer herbivory in that Key deer tend to aggregate in urban environments, which increased browsing pressure in adjacent hammock habitats. Fire played an important role by increasing the percent cover of preferred herbaceous species in pinelands especially in deer exclosure plots. Fire and Key deer browsing also interacted by decreasing hardwood species invasion into pineland habitat. Key deer have a strong influence on plant community structure on islands with large deer herds. Management efforts, such as contraception, public education on the ramifications of feeding wildlife, and sustainable/suspended development of lands in the National Key Deer Refuge is warranted to benefit Key deer and to deter increased browsing pressure.

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