Year

2006

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)

Department

Biology

First Advisor

Dr. Joseph A. Butler

Second Advisor

Dr. J. Mitchell Lockhart

Department Chair

Dr. Joseph A. Butler

Abstract

The purpose of this research was to study the potential negative effects that mesopredators have on their environment and to promote control of mesopredator populations. Overabundant predatory species such as the raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana) can have significant pernicious effects on populations of autochthonous prey species, particularly when super predators such as the red wolf (Canis rufus) and Florida panther (Felis concolor coryii) are absent. These overabundant species, coined as mesopredators, are often responsible for extreme levels of predation on prey species and/or their young. The mesopredator release hypothesis involves the "release" or increased density of a generalist/opportunistic consumer species. This release hypothesis has two main predictions: first the absence of top predators lowers nest success of prey populations; the second there is a subsequent positive relationship between hyperabundant mesopredators and nest/prey predation. This phenomenon occurs because super predators such as the wolves and big cats have been driven to extinction or extirpation.

To study the effects of mesopredators I used several approaches. Overabundant raccoons (29) were removed from a known diamondback terrapin (Malaclemys terrapin centrata) nesting beach to evaluate the reduction in terrapin nest predation. Next, I studied age structure, stomach content, and parasite load of the removed raccoons to determine several criteria. By determining the negative impacts such as over-predation of listed and ecologically important species and mesopredator potential to spread infectious diseases and parasites, I hope to promote population control of these animals.

Analysis of sex ratios showed that adult males dominant (6/23). Gut content analysis showed that raccoons partook in over 11 different prey items including terrapin hatchlings. The parasite load included five nematode species, one acanthocephalan, and one cestode, and two protozoan parasites. Several parasites found pose a threat to human health and the control of such species is a concern.

By studying mesopredator life history traits (population age, diet, and parasite population) we hope to understand the various negative effects it may place upon its environment. With this knowledge, further research and possible control methods may be proposed.

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