Date of Award

5-2007

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Malcolm L. Hunter Jr.

Second Committee Member

Aram J. K. Calhoun

Third Committee Member

James P. Gibbs

Abstract

Changes in forest habitat have been linked to global declines in amphibian populations, but little research has been conducted into the mechanisms causing these declines. This study evaluated the effects of changes in forest habitat on the spatial distribution of a Maine amphibian community, focusing on juvenile wood frogs, Rana sylvatica. Juvenile wood frogs emerging from artificial ponds did not orient towards preferred habitat and a significant number of animals maintained the same directionality documented at the site from which larval individuals were collected. Abundance and habitat use differed among adults of 9 species of amphibians in a replicated landscape (n = 4, each 10 ha in size) of 4 forestry treatments (clearcut with coarse woody debris [CWD] removed, clearcut with CWD retained, partial-cut of 50% of canopy cover, and an uncut control) centered on a breeding pool. Lower captures of juveniles of all species (statistically significant for 7 of 9 species) were seen in clearcuts compared to forested treatments. Juvenile wood frogs marked as they emerged from the breeding pools preferred forested treatments to the clearcuts, but patterns of captures within each treatment at different distances from the pond’s edge did not differ. The response of juvenile wood frogs to habitat heterogeneity (in the 10 ha landscapes, a 12x16 m area of hexagonal patches, 1x4 m pens, and a 10x10 m pen) changed from coarse scale habitat selection during emigration, to fine scale selection when settling. Spatial simulations designed to predict the effects of habitat change on the spatial distribution of juvenile wood frogs best predicted field data when specific movement behavior, and a heterogeneous landscape were included. Model results demonstrated the importance of comparing densities of frogs in different habitat types following emigration, as well as the distribution of frogs over distance when considering effects of habitat change on local populations. The study demonstrated the complex responses of amphibians to habitat change and the importance of conducting research at multiple spatial and temporal scales. Simulations highlighted the need for species-specific information when predicting the effects of habitat change on the spatial distribution of amphibians, and managing habitat accordingly.

Download

Share