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CASCADING EFFECTS OF PREDATOR REMOVAL ON THE ECOLOGY OF SEA TURTLE NESTING BEACHES
Title
CASCADING EFFECTS OF PREDATOR REMOVAL ON THE ECOLOGY OF SEA TURTLE NESTING BEACHES.
Creator
Barton, Brandon, Roth, James, University of Central Florida
Abstract / Description
Traditional views of food web dynamics have characterized species interactions as linear and direct. However, modern food web theory suggests that interactions can also be nonlinear and indirect, so that disturbance at one trophic level is transmitted throughout the community. Many previous studies have demonstrated that the removal of top predators from terrestrial ecosystems can have broad-scale impacts on community ecology. I examined the direct and indirect effects of raccoon removal from...
Show moreTraditional views of food web dynamics have characterized species interactions as linear and direct. However, modern food web theory suggests that interactions can also be nonlinear and indirect, so that disturbance at one trophic level is transmitted throughout the community. Many previous studies have demonstrated that the removal of top predators from terrestrial ecosystems can have broad-scale impacts on community ecology. I examined the direct and indirect effects of raccoon removal from sea turtle nesting beaches in east-central Florida during the summers of 2003 and 2004. Raccoon and ghost crab predation are among the highest causes of egg mortality for sea turtles in Florida and raccoons are intraguild predators of ghost crabs. Because of the damage done to sea turtle nests, raccoons have been removed from some beaches during the sea turtle nesting season. I compared the diet and demography of a raccoon population that had experienced two decades of raccoon removal to a population that had previously been unmanipulated. I found that long-term raccoon removal had created a significantly male-biased sex ratio in that population. I also examined the indirect effects of raccoon removal by comparing the abundances of raccoons and ghost crabs at four study sites using passive tracking plots. My data suggest intraguild predation by raccoons limits ghost crab abundance and that reduced raccoon abundance allowed ghost crab abundance to increase, resulting in a net increase in sea turtle egg predation. These results support my hypothesis that intraguild predation of ghost crabs by raccoons is an influential interaction on sea turtle nesting beach community dynamics.
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Date Issued
2005
Identifier
CFE0000521, ucf:46466
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000521
FACTORS AFFECTING PREDATION OF MARINE TURTLE EGGS BY RACCOONS AND GHOST CRABS ON CANAVERAL NATIONAL SEASHORE, FL
Title
FACTORS AFFECTING PREDATION OF MARINE TURTLE EGGS BY RACCOONS AND GHOST CRABS ON CANAVERAL NATIONAL SEASHORE, FL.
Creator
Brown, Justin, Roth, James, University of Central Florida
Abstract / Description
Changes in abundance of interactive species can have cascading, community-wide effects (Soulé et al. 2003). Raccoons (Procyon lotor) prey on a competitor for marine turtle eggs, the Atlantic ghost crab (Ocypode quadrata). Conservation of marine turtles often includes managing raccoons--the most obvious egg predator--which may have broader ecological effects, and unknown effects on egg predation. Neither the relationship between raccoons and ghost crab density nor the effects of ghost...
Show moreChanges in abundance of interactive species can have cascading, community-wide effects (Soulé et al. 2003). Raccoons (Procyon lotor) prey on a competitor for marine turtle eggs, the Atlantic ghost crab (Ocypode quadrata). Conservation of marine turtles often includes managing raccoons--the most obvious egg predator--which may have broader ecological effects, and unknown effects on egg predation. Neither the relationship between raccoons and ghost crab density nor the effects of ghost crab density on egg predation are well understood. I studied raccoon-ghost crab interactions and the effects of environmental variation on their activity during the 2007 marine turtle nesting season on Canaveral National Seashore, FL. My goal was to model predator activity and identify efficient management strategies to reduce egg predation. Raccoon activity increased with increasing habitat diversity and edge of the dominant cover type, coastal strand. Raccoon activity increased locally and became less variable near segments of beach accessed for human recreation, but activity was greater on undeveloped beach, where habitat diversity and edge were greater. Ghost crab density and size were primarily affected by sand characteristics and recreation but decreased with increasing raccoon activity in June, which may have contributed to sustained declines in ghost crab density. Hatching success of marine turtles decreased with increasing ghost crab egg predation, suggesting ghost crabs are an important cause of egg mortality and not merely scavengers on unhatched eggs. Egg predation by ghost crabs was unrelated to ghost crab density or size, likely a result of monitoring limitations, but raccoon activity increased with increasing egg predation by ghost crabs, supporting previous research and experimental evidence suggesting ghost crabs can facilitate secondary nest predation by raccoons. This indirect interaction has strong implications for marine turtle conservation, because its strength may increase with increasing ghost crab density, potentially negating the effects of raccoon removal.
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Date Issued
2009
Identifier
CFE0002667, ucf:48235
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002667
Estimated diets, diet overlap, and winter habitat associations of four grassland sparrows in Florida dry prairie
Title
Estimated diets, diet overlap, and winter habitat associations of four grassland sparrows in Florida dry prairie.
Creator
Korosy, Marianne, Noss, Reed, Quintana-Ascencio, Pedro, Roth, James, Hinkle, Ross, Bowman, Reed, University of Central Florida
Abstract / Description
North American grassland birds show long-term population declines that generally exceed the declines of other bird groups. Efforts to conserve grassland birds require knowledge of diet and habitat requirements during both the breeding and nonbreeding periods of annual life cycles. This dissertation investigated sparrow habitat associations within two defined plant communities of the dry prairie ecosystem, the dry-mesic and wet-mesic prairie, for four prescribed fire treatments over two...
Show moreNorth American grassland birds show long-term population declines that generally exceed the declines of other bird groups. Efforts to conserve grassland birds require knowledge of diet and habitat requirements during both the breeding and nonbreeding periods of annual life cycles. This dissertation investigated sparrow habitat associations within two defined plant communities of the dry prairie ecosystem, the dry-mesic and wet-mesic prairie, for four prescribed fire treatments over two consecutive winters. Grasshopper and Henslow's sparrows showed higher relative abundance in wet-mesic prairie and Bachman's Sparrows were more abundant in dry-mesic prairie across all fire treatments. Abundances of Grasshopper and Bachman's sparrows were best predicted by plant community association and secondly by time since fire; whereas for Henslow's Sparrows, habitat and time since fire were equally important. Fall molt-period diets and diet overlap were modeled for resident Florida Grasshopper and Bachman's sparrows using stable carbon and nitrogen isotope ratios of bird feathers and potential food sources, e.g., arthropods and seeds. Grasshoppers (Orthoptera, including a variety of species foraging on both C3 and C4 herbs), spiders, dragonflies, flies, beetles and weevils comprised the majority of the diets of adult and juvenile Florida Grasshopper Sparrows and Bachman's Sparrows, but in differing proportions. Despite the similarity in reconstructed diets for the two sparrow species, analysis of diet overlap suggested that approximately half of the Florida Grasshopper Sparrows had diets consisting of higher trophic level prey than Bachman's Sparrows. Winter diets and diet overlap among Grasshopper, Henslow's, and Bachman's sparrows were reconstructed using stable carbon and nitrogen isotope ratios of feathers and potential arthropod and seed food sources. Sparrows were captured and recaptured in winter 2007-2008 using systematic flush-netting, removing a tail feather at first capture and then removing the regrown feather when birds were recaptured. Winter diets of all three sparrows included a variety of arthropods, grass seeds, and sedge seeds, but Bachman's Sparrow winter diets spanned greater trophic diversity than either of the migratory sparrows. Estimated diets of Henslow's and Grasshopper sparrows differed from that of Bachman's Sparrow but Henslow's Sparrow diets did not differ from Grasshopper Sparrow diets. This is the first study of fall and winter sparrow diets in Florida based on stable isotopes and the first study in peninsular Florida on habitat associations of ground-dwelling sparrows.
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Date Issued
2013
Identifier
CFE0005363, ucf:50475
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005363
Migratory connectivity and carry-over effects in Northwest Atlantic loggerhead turtles (Caretta caretta, L.)
Title
Migratory connectivity and carry-over effects in Northwest Atlantic loggerhead turtles (Caretta caretta, L.).
Creator
Ceriani, Simona, Weishampel, John, Ehrhart, Llewellyn, Walters, Linda, Quintana-Ascencio, Pedro, Roth, James, Valdes, Eduardo, University of Central Florida
Abstract / Description
Migration is a widespread and complex phenomenon in nature that has fascinated humans for centuries. Connectivity among populations influences their demographics, genetic structure and response to environmental change. Here, I used the loggerhead turtle (Caretta caretta, L.) as a study organism to address questions related to migratory connectivity and carry-over effects using satellite telemetry, stable isotope analysis and GIS interpolation methods. Telemetry identified foraging areas...
Show moreMigration is a widespread and complex phenomenon in nature that has fascinated humans for centuries. Connectivity among populations influences their demographics, genetic structure and response to environmental change. Here, I used the loggerhead turtle (Caretta caretta, L.) as a study organism to address questions related to migratory connectivity and carry-over effects using satellite telemetry, stable isotope analysis and GIS interpolation methods. Telemetry identified foraging areas previously overlooked for loggerheads nesting in Florida. Next, I validated and evaluated the efficacy of intrinsic markers as a complementary and low cost tool to assign loggerhead foraging regions in the Northwest Atlantic Ocean (NWA), using both a spatially implicit and spatially explicit (isoscapes) approach. I then focused on the nesting beaches and developed a common currency for isotopic studies based on unhatched eggs, which provide a non-invasive and non-destructive method for more extensive sampling to elucidate isotopic patterns across broader spatiotemporal scales. Lastly, I found that intra-population variations in foraging strategies affect annual and long-term reproductive output of loggerheads nesting in Florida. Understanding geospatial linkages is critical to the fostering of appropriate management and conservation strategies for migratory species. My multi-faceted approach contributes to the growing body of literature exploring migratory connectivity and carry-over effects.
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Date Issued
2014
Identifier
CFE0005470, ucf:50390
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005470