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Evidence for disease-related amphibian decline in Colorado

Biological Conservation

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Abstract

The recent discovery of a pathogenic fungus (Batrachochytrium dendrobatidis) associated with declines in frogs in the American and Australian tropics, suggests that at least the proximate cause, may be known for many previously unexplained amphibian declines. We have monitored boreal toads in Colorado since 1991 at four sites using capture-recapture of adults and counts of egg masses to examine the dynamics of this metapopulation. Numbers of male toads declines in 1996 and 1999 with annual survival rate averaging 78% from 1991 to 1994, 45% in 1995 and 3% between 1998 and 1999. Numbers of egg masses also declines. An etiological diagnosis of chytridiomycosis consistent with infections by the genus Batrachochytrium was made in six wild adult toads. Characteristic histomorphological features (i.e. intracellular location, shape of thalli, presence of discharge tubes and rhizoids) of chytrid organisms, and host tissue response (acanthosis and hyperkeratosis) were observed in individual toads. These characteristics were indistinguishable from previously reported mortality events associated with chytrid fungus. We also observed epizootiological features consistent with mortality events associated with chytrid fungus: an increase in the ratio of female:male toads captured, and apparent spread of mortalities within the metapopulation and mortalities restricted to post metamorphic animals. Eleven years of population data suggest that this metapopulation of toads is in danger of extinction, pathological and epizootiological evidence indicates that B. dendrobatidis has played a proximate role in this process.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Evidence for disease-related amphibian decline in Colorado
Series title:
Biological Conservation
Volume
110
Issue:
3
Year Published:
2003
Language:
English
Publisher:
U.S. Fish and Wildlife Service
Contributing office(s):
Fort Collins Science Center
Description:
p. 357-365
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Biological Conservation
First page:
357
Last page:
365