Effect of Amphibian Chytrid Fungus on the Size Distribution of Boreal Toads in Rocky Mountain National Park
Abstract
Amphibians have unique physical characteristics that
increase their susceptibility to environmental disturbances.
Their permeable skin and ectothermic manner of
thermoregulation coupled with pathogen exposure are
contributing factors to the global decline of amphibians.
Additionally, most amphibians are biphasic, meaning they
have two distinct habitat requirements over the course of
their life. An aquatic environment is required for
reproduction, while feeding and wintering as adults takes
place on land. Amphibian chytrid fungus Batrachochytrium
dendrobatidis (Bd), is a skin pathogen affecting amphibian
populations globally, including the endangered populations
of boreal toads in Rocky Mountain National Park (RMNP) in
Colorado. We conducted population monitoring in tandem
with size measurements of individual boreal toads found at
two sites in RMNP. Lost Lake is a site that tests positive for
Bd, (Fig. 1) and Spruce Lake is a site with no evidence of
Bd (Fig. 2). Male and female toads found in the presence of
Bd at Lost Lake had shorter snout-to-vent length (SVL)
measurements and lower mass, suggesting that Bd may
impact body size. Reproductive capacity may be altered by
body size, so understanding the relationship between Bd
and body size is important for species conservation of
endangered boreal toads.