Counting Amphibians Before They Hatch
by Mary ThillBefore he moved to the Adirondacks four years ago, David Patrick studied how to reduce roadkill of salamanders, frogs and reptiles downstate, and the effects of harvesting chameleons for the pet trade in Tanzania, where rainforest species are confined to some of the smallest ranges in the world.
“When I came here one of the things that struck me was the sheer abundance of amphibians,” says Patrick, who is director of the Center for Adirondack Biodiversity at Paul Smith’s College. “As a conservation biologist, most of the stuff I’ve done in the past is really crisis management. So, you come to the Adirondacks and essentially there are fewer crises here.”
Which makes the Adirondacks unusual, and interesting to a scientist. “The beauty of the Adirondacks is the ability to ask questions in an intact landscape,” says Patrick. There are acres and acres of undisturbed wetlands and forests, and not many roads or buildings to get in the way if a creature needs to move.
This spring Patrick and nine undergraduate students set out to try to count every wood frog and spotted salamander in 12 square kilometers at the Paul Smith’s College Visitor Interpretive Center (VIC). Why? Because it’s there, basically: the rare opportunity to study an ecosystem that is largely unchanged by humans. And to provide a useful comparison for other places that are losing species to habitat change.
“As far as I’m aware, this is the first estimate of spring-breeding amphibian biomass in an intact wetland system at a landscape scale that has been done,” Patrick says and laughs. “So we set out, and I confess I thought it was just crazy. But it was great fun.”
Between April 30 and May 8 the crew scoured the VIC for every ephemeral pool and beaver pond they could find. Wood frogs and spotted salamanders live unseen on the forest floor most of the year, but as the snow melts they seek out water where fish and other predators are not established. Spotted salamanders rarely lay eggs in a large lake, Patrick says. Wood frogs never do.
Traveling on foot and seeking out shallow waters on calm days when they could see egg masses, Patrick and his students found 68 breeding sites at the VIC and in the watershed of nearby Smitty Creek, a longtime study site of Paul Smith’s biology students. They counted 2,484 wood frog egg masses, and 1,272 spotted salamander egg masses. Each wood frog egg mass signals the presence of one female, but spotted salamander output varies. A final tally will entail extrapolation and formulas. Assuming a 1:1 sex ratio, the next step is to estimate a number of adults and juveniles and to calculate their collective weight.
Another reason for this exercise is to establish a comparison for the future. On a recent Monday morning, before walking upstairs to his office in the Countess Alicia Spaulding-Paolozzi Environmental Research and Education Center on the shore of Lower St. Regis Lake, Patrick stopped into his lab on the ground level. Wood frog tadpoles resembling fat commas and slender spotted salamander larvae wiggled in a dozen plastic storage containers, the water in the bins at different temperatures.
Patrick has several Adirondack amphibian studies under way. He is interested in how mink frogs and other semi-aquatic transformers react to temperature change. Amphibians are breeding earlier in the Northeast, and their dependence on shallow water early in life may make them vulnerable to changes in seasonal warming and precipitation.“One of the things, when we talk about why amphibians are so important, is they take aquatic biomass and bring it up onto land, so you have a nutrient transfer from aquatic to terrestrial systems,” Patrick explains. “So when I write in my next grant application that these animals are really important, I’ll be able to say how important they are.”