Year of Award

2009

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Fish and Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Co-chair

Andrew Sheldon, Lisa Eby

Commitee Members

Winsor Lowe, Scott Mills, Stephen Corn

Keywords

Amphibian, Batrachochytrium dendrobatidis, Montana, Predictive Modeling, Reptile, Status Assessment

Abstract

Beginning in the late 1980s herpetologists began to realize that amphibians around the world had undergone, and were continuing to undergo, declines, extirpations, and extinctions. In most cases, detections of declines and determinations of the underlying causes has been hampered by a lack of available baseline information on distribution and status. This project was a cooperative effort to address these data deficiencies for amphibians and reptiles in Montana. Watersheds with greater than 30 percent federal or state land ownership were randomly selected for survey in each of 11 geographic strata. Visual encounter and dipnet surveys of all standing water bodies on public lands within these watersheds yielded watershed and site occupancy estimates as a measure of status. Occupancy estimates from this first-ever state-wide base level assessment can be more validly used for future comparisons with future status assessment, provided additional support for declines in Western Toad (Bufo boreas) and Northern Leopard Frog (Rana pipiens) populations in western Montana, and identified a variety of conservation issues of concern that can be addressed through management actions (e.g., clear evidence for negative impacts of fish and importance of maintaining natural disturbance regimes such as flooding, beaver, and fire). The information gathered during field inventories was combined with other existing information and used in maximum entropy modeling to predict state-wide distribution and habitat suitability for all of Montana's amphibians and reptiles. These models out performed GAP analysis models by simultaneously reducing the area predicted and omission error rates. Among other things, models identified scale dependent responses to environmental variables, potentially isolated populations in need of conservation efforts, and areas that are critical for maintaining landscape connectivity. In conjunction with field inventories, a state-wide assessment of the distribution of the pathogenic chytrid fungus (Batrachochytrium dendrobatidis) (Bd) was undertaken using PCR-based detection in skin swabs or tissue samples. Bd was found across Montana in 6 of the 9 species tested at a variety of elevations, habitats, and distances from human activities. The widespread presence of Bd highlights the need for additional studies and measures to prevent the spread of Bd and other novel pathogens.

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© Copyright 2009 Bryce Alan Maxell