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.

The purpose of my research was to test the hypothesis that the availability of fresh, naturally occurring water may limit the distribution of Florida Key Deer (Odocoileus virginianus clavium). More specifically, I was trying to determine if there was enough fresh, drinkable water for the deer on each of the islands. To test the hypothesis, I developed a model that simulated likely seasonal fluctuations in fresh water availability in naturally occurring waterholes within the Key Deer range. I estimated 60 scenarios representing different weather (precipitation and evaporation) conditions, different literature estimates of the daily water requirement of Key Deer and also different upper salinity thresholds for drinkable water. Results showed that 1) even under the most favorable conditions in terms of fresh water availability, there was not enough fresh, drinkable water for the deer on any of the islands. Results also showed that 2) high salinity was important in determining the fresh water availability to the deer, in addition to the lack of water volume. Although these results suggest a prolonged seasonal shortage of fresh, naturally occurring water on each of the islands, deer were present on all of the islands during all seasons. One possible reason for the lack of correlation between Key Deer distribution and naturally occurring waterholes is the availability of man-made water sources (e.g. birdbaths, swimming pools).

The purpose of my research was to test the hypothesis that the availability of fresh, naturally occurring water may limit the distribution of Florida Key Deer (Odocoileus virginianus clavium). More specifically, I was trying to determine if there was enough fresh, drinkable water for the deer on each of the islands. To test the hypothesis, I developed a model that simulated likely seasonal fluctuations in fresh water availability in naturally occurring waterholes within the Key Deer range. I estimated 60 scenarios representing different weather (precipitation and evaporation) conditions, different literature estimates of the daily water requirement of Key Deer and also different upper salinity thresholds for drinkable water. Results showed that 1) even under the most favorable conditions in terms of fresh water availability, there was not enough fresh, drinkable water for the deer on any of the islands. Results also showed that 2) high salinity was important in determining the fresh water availability to the deer, in addition to the lack of water volume. Although these results suggest a prolonged seasonal shortage of fresh, naturally occurring water on each of the islands, deer were present on all of the islands during all seasons. One possible reason for the lack of correlation between Key Deer distribution and naturally occurring waterholes is the availability of man-made water sources (e.g. birdbaths, swimming pools).

Recent improvements in genetic analyses have paved the way in using molecular data to answer questions regarding evolutionary history, genetic structure, and demography. Key deer are a federally endangered subspecies assumed to be genetically unique (based on one allozyme study), homogeneous, and have a female-biased population of approximately 900 deer. I used 985bp of the mitochondrial cytochrome b gene and 12 microsatellite loci to test two hypotheses: 1) if the Moser Channel is a barrier to gene flow, I should expect that Key deer are differentiated and have reduced diversity compared to mainland deer and (2) if isolation on islands leads to a higher probability of extinction, I should expect that Key deer exhibit a small population size and a high risk of extinction. My results indicate that Key deer are genetically isolated from mainland white-tailed deer and that there is a lack of genetic substructure between islands. While Key deer exhibit reduced levels of genetic diversity compared to their mainland counterparts, they contain enough diversity of which to uniquely identify individual deer. Based on genetic identification, I estimated a census size of around 1,000 individuals with a heavily skewed female-biased adult sex ratio. Furthermore, I combined genetic and contemporary demographic data to generate a species persistence model of the Key deer. Sensitivity tests within the population viability analysis brought to light the importance of fetal sex ratio and female survival as the primary factors at risk of driving the subspecies to extinction.