Wood frogs

Wood frog
A sleepy wood frog equipped with a radio tracker. Photo by Jason O’Connor.

If Jason O’ Connor’s work were not so  grounded in science, it might seem like something out of a horror story. O’Connor, a native of North Carolina and an MS candidate studying with Tracy Rittenhouse, assistant professor in the Department of Natural Resources and the Environment, is monitoring the seasonal life and death transformations of tiny wood frogs and assessing the effects of climate change on them.

These amphibians freeze solid in winter. Their bodies turn to ice. The frogs are essentially dead, but, when temperatures warm, they thaw out and completely revive. O’Connor is gathering data to learn precisely how the frogs use this amazing process to survive winter.

“Wood frogs are the rare vertebrates whose hearts can stop. They can freeze and thaw and come back to life. I’m looking at how draining it is to the frogs’ survival to go through the process repeatedly,” O’Connor says.

As an undergraduate biology major at the University of Miami, O’Connor got his first taste of the rigors and joys of academic fieldwork. He assisted with a project in the Everglades and then worked on a study of cotton mice. An internship at the Archbold Biological Station involved a study on the distribution of the invasive African jewelfish.

O’Connor is now engaged in looking at the effects of soil moisture and temperature variation as related to the winter survival of wood frogs. He is working at two sites, one at the College’s Spring Hill Farm and another in the nearby Nathan Hale Forest, studying 34 wood frogs at each site.

On a chilly winter afternoon, the wire enclosures equipped with temperature data monitors, built between October and December to hold the frogs, contained piles of damp leaves. Digging through the leaf litter, O’Connor reveals the outline of a small frog, stretched out and covered in ice. Attached to the animals are small radios to track their movements.

“I was surprised to find that they are active during warm, wet periods in January. One sunny day I found they were hopping around in the enclosures,” O’Connor says with obvious admiration for his study subjects.

Jason O'Connor
Jason O’Connor

Although there have been other studies of wood frogs, O’Connor is looking at whether wood frogs select their winter homes based on soil moisture or temperature conditions and to what degree these factors affect their survival. Some of the enclosures are in wetter and some in drier places.

“We live in a changing world and I’m trying to understand how species respond to changes in the environment. This study looks at how they react to soil moisture and temperature now and in the future. Hopefully this work will inform conservation planning for wood frogs and other similar amphibians,” O’Connor adds.

Soon the first warm spring rain will begin to fall and the wood frogs in O’Connor’s study will start moving toward vernal pools. They will awaken from their long winter sleep and look for food and mates. Before they do, O’Connor will count the survivors and weigh them to see how much the winter has depleted them.

A vernal pool can support hundreds of breeding adults. When the pools burst with the distinctive sounds of peepers, wood frogs, bullfrogs and other clarions of spring, it will be especially meaningful for Master’s degree student Jason O’Connor. The data he has compiled adds to scientific knowledge and gives us a deeper understanding of a tiny frog that challenges our conventional definitions of life and death.

By Nancy P. Weiss