How will amphibians respond to climate change? The research ponds at a University of Michigan forest preserve may hold some clues. Biologists there found that common wood frogs breed earlier and produce fewer eggs after warmer winters, and the tadpoles develop more slowly.
Michael Benard, assistant professor of biology at Case Western Reserve University and formerly a Michigan Fellow at the U-M Department of Ecology and Evolutionary Biology, also found that frogs produce more eggs during winters with more rain and snow.
As the world warms, scientists have documented that many species are breeding earlier. But few field studies have evaluated the extent to which breeding early affects the growth, development and survival of individuals, according to Benard, the author of a paper on the topic published online Sept. 29, 2014, in Global Change Biology.
The study of the links between climate and the timing of biological events – such as bird migration, plant flowering or the breeding of wood frogs – is called phenology.
"Amphibians are one group for which it is important to understand the impacts of phenological shifts. They are declining globally, and climate change is predicted to be an increasingly important threat to amphibians in the coming years," said Benard, who began his wood frog study at six ponds in U-M's E.S. George Reserve, a 1,300-acre research station in southwestern Livingston County, near Pinckney. The study continues in northeast Ohio.
Benard found that when wood frogs breed early, their offspring have delayed development but still metamorphose earlier in the year. He identified the broad patterns by examining and tracking important life events of more than 50,000 juvenile and hundreds of adult wood frogs over seven years and comparing the data to winter weather records. Temperatures were recorded at a nearby weather station.
Benard is the George B. Mayer Chair in Urban and Environmental Studies and an assistant professor of biology at Case Western Reserve University. The University of Michigan, the Michigan Society of Fellows and Case Western Reserve University provided support and funding for the research.