by feeding off of the keratin produced by the amphibian, which causes keratosis. Keratosis then can either suffocate the amphibian, or cause it to go into cardiac arrest. This can be detrimental to amphibians because it inhibits their ability to absorb water and electrolytes. In Boreal Toads, the effects of the chytrid fungus are highly variable, with some populations experiencing total extirpation due to exposure and others experiencing a chronic disease cycle in which low transmission rates lead to a 5% year to year population decrease. These differences in effect are due to complex host-pathogen relationships between the chytrid fungus, the toads, aquatic environment, temperature, population size, and elevation. As climate change shifts all of these variables, the chytrid fungus is expected to be a stronger presence in many Boreal Toad populations. Reintroduction efforts Attempts to reintroduce Boreal Toads to both previously occupied and new locations has had mixed results. In Colorado, almost all attempts at repatriation or translocation of mature individuals or eggs have failed. These studies have failed to result in a diverse age structure of mature adults, especially lacking in sexually mature individuals. However, more recent reintroduction attempts have proven successful with a mature individual translocation effort made in Utah in 2019 and a tadpole reintroduction effort made in Colorado in 2019 also. The success of these efforts is due to innovations made in their processes. In the Utah project, they utilized the benefits of small refugia-like population dynamics. Chytrid fungus is known to spread at much lower rates in smaller populations, so by introducing smaller amounts of toads to these isolated locations, the chytrid effect was lowered. In the Colorado project, the utilized a probiotic bath for the tadpoles called "Purple Rain" that strengthened the skin microbiome of the tadpoles, providing resistance to chytrid fungus. References Further reading Carey, Cynthia, Judsen E. Bruzgul, Lauren J. Livo, Margie L. Walling, Kristin A. Kuehl, Brenner F. Dixon, Allan P. Pessier, Ross A. Alford, and Kevin B. Rogers. "Experimental Exposures of Boreal Toads (Bufo Boreas) to a Pathogenic Chytrid Fungus (Batrachochytrium Dendrobatidis)." EcoHealth 3.1 (2006): 5–21. Anaxyrus Fauna of the Western United States Fauna of the Rocky Mountains