Behavioral choice and demographic consequences of wood frog habitat selection in response to land use

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on February 28, 2008)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2007.Land use is a pervasive form of disturbance affecting natural systems on Earth. My dissertation research is set within the context of a large scale project referred to as Land-use Effects on Amphibian Populations (LEAP), where researchers in Maine, Missouri, and South Carolina are determining the effects of timber harvest on the persistence of amphibian populations. The purpose of my dissertation research was to define adult wood frog nonbreeding habitat in continuous oak-hickory forest and in response to timber harvest. I asked research questions that address the two components of habitat selection: 1) the behavioral choice, and 2) the demographic consequences of that choice. To document behavioral choice, I allowed adults to move freely throughout the circular experimental timber harvest arrays (164 m radius) by using standard radiotelemetry techniques. Prior to timber harvest, I found that wood frogs were not distributed equally throughout oak-hickory forest. Adults used drainages as non-breeding habitat. In addition, the number of frogs that migrated to a specific drainage correlated with the distance between the pond and the drainage. Following timber harvest wood frogs avoided clearcuts and increased movement rates in response to timber harvest. Further, I confirmed the consistency of this behavioral response by conducting experimental displacements and found that adults exhibit site fidelity to non-breeding habitat. Frogs displaced to the center of clearcuts evacuated the clearcuts in one night of rain and 20 of 22 frogs displaced back to the pond returned to the same drainage.To determine demographic consequences, I estimated survival of frogs constrained within microhabitats. Desiccation risks for frogs located on forested ridgetops or in exposed areas within clearcuts were severe. Brushpiles within clearcuts provided microhabitats with similar desiccation risks as microhabitats within forested drainages. I also determined survival of transmittered frogs that moved freely among microhabitats by radio-tracking 117 frogs over 3 years. I documented 29 predation events, 13 desiccation events, and 8 mortalities of unknown cause. Using Coxproportional hazard models, I found that survival within the timber harvest array was 1.7 times lower than survival within continuous forest. Survival was lowest during the drought year of 2005 when all desiccation events occurred. My results indicated that predation and desiccation risks near the breeding ponds are ecological pressures that explain why adult amphibians migrate away from breeding habitat during the nonbreeding season.Includes bibliographical references

Desiccation rates of Rana sylvatica, Rana clamitans, and Bufo americanus in a fragmented forest

Abstract only availableHabitat loss and fragmentation are the primary causes in the declines of amphibian populations. Farming, urban sprawl, and logging have created a mosaic of developed and undeveloped land that may create barriers between aquatic breeding sites and terrestrial refuges. While ponds and wetlands are important in early development and breeding, many species spend their adult lives foraging in the terrestrial environment surrounding a breeding site. An amphibian's ability to move and forage in a terrestrial environment is determined by their capacity to remain hydrated. We compared desiccation rates of wood frogs (Rana sylvatica), green frogs (Rana clamitans), and American toads (Bufo americanus) juveniles in different microhabitats of a forest and a clear-cut to determine how they might affect the terrestrial activity of amphibians. Using the experimental arrays created by LEAP (Land use Effects on Amphibian Populations) at Daniel Boone Conservation Area we set up cylindrical wire mesh enclosures in forest drainages, forest ridges, brush piles in clear cuts, and open areas in clear cuts at two ponds. Animals were placed in the enclosures during the evening and weighed every six hours for twenty-four hours. Soil moisture, and soil temperature were also measured every six hours. Analysis of variance with repeated measures was used to compare percent water loss in the habitat treatments. All frogs lost water; however, water loss was greater in the day compared to night. Brush piles within the clear cut slowed water loss compared to open areas in the clear cuts, and animals on forest ridges lost more water than those in forest drainages. Our results reinforce the need to protect forest drainages as terrestrial refuges and illustrate that clear cutting, even with brush piles as cover, may negatively affect the delicate balance of mortality and survivorship in juveniles, therefore threatening the future of a population.Life Sciences Undergraduate Research Opportunity Progra

Effects of Timber Harvest on Amphibian Populations: Understanding Mechanisms from Forest Experiments

Accompanying appendix may be accessed at: http://hdl.handle.net/10355/1365Harvesting timber is a common form of land use that has the potential to cause declines in amphibian populations. It is essential to understand the behavior and fate of individuals and the resulting consequences for vital rates (birth, death, immigration, emigration) under different forest management conditions.We report on experimental studies conducted in three regions of the United States to identify mechanisms of responses by pond-breeding amphibians to timber harvest treatments. Our studies demonstrate that life stages related to oviposition and larval performance in the aquatic stage are sometimes affected positively by clearcutting, whereas effects on juvenile and adult terrestrial stages are mostly negative

Effects of Timber Harvest on Amphibian Populations: Understanding Mechanisms from Forest Experiments. Appendix

Appendix only of an article to be published in BioScience by the American Institute of Biological Sciences.The Appendix provides a summary of results for four forest management treatments according to region, species, and response variables

Pond-Breeding Amphibian Community Composition in Missouri

Description of data: Site location data and amphibian species and numbers per life stage encountered at each research site in Missouri. Collected: 2002, 2005, 2006, 2012. Collection site: Missouri. Method: Collected from drift fences around ponds in 2002, 2005; dipnet and funnel traps in 2006, 2012