The stress of drought is acutely felt by aquatic animals such as salamanders. The extreme drought in the southeastern United States in 2007-2008 provided an opportunity to study how salamanders react and survive during such dry conditions. It also gave us clues as to how salamanders and other aquatic organisms may react to global warming.
The journal Herpetologica reports on a 5-year study of the Northern Dusky Salamander, common to eastern North America. From 2005 to 2009, including two severe drought years, the presence of salamanders was recorded at 17 first-order streams in the Piedmont region of North Carolina. Data on the amphibians' presence were established by capturing, marking, and recapturing salamanders over the course of the study.
Researchers found that the adult salamanders had a high rate of survival over the course of the study, even during the drought years. The abundance of larval salamanders, however, decreased by an average of 30 percent during the drought. This differential mortality suggests a between-generation survival strategy, with the high survival rate of adults mitigating the effect of drought on the numbers of larvae.
During the extreme drought, water levels reached a 110-year low. Many streams were dry for periods of 2 to 3 months at a time, reduced to pools rather than flowing water. These conditions brought about another survival strategy, temporary migration of adult salamanders -- at twice the rate of non-drought years. They moved from stream beds to underground or high-humidity refuges. Crayfish burrows and rocks provided shelter from the hot and dry conditions.
Because climate change is expected to bring warming trends and more drought, this study offers implications for the survival of stream-dwelling salamanders. An increase in the mortality of larvae, or early metamorphosis, could mean declines in salamander fitness and size.
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