Beneath the Ice

View of the frozen landscape that comes to Acadia every winter.

NPS Photo

Many imagine the winter in Acadia to be snowy and cold. Though the average low temperatures fluctuate around 12°F in the winter months, Acadia National Park rarely sees more than 15 to 20 days per season where the snowfall exceeds one inch. This minimal snowfall in comparison to inland Maine is a result of Acadia’s location on the coast. Low temperatures and icy conditions tend to define an Acadian winter. Most bodies of water in the park freeze, including Jordan Pond, the deepest lake in the park. These frozen lakes sometimes provide great opportunities for ice fishing and ice skating. While park visitors enjoy the winter activities on the ice and in the occasional snow, some of Acadia’s most resilient animals are surviving frozen beneath the ice.

Adaptations for Winter

Bound to both the water and the land, frogs and turtles must uniquely adapt to the frozen wonderland that is Acadia in the winter. Unlike fish, these animals need to breathe air in order to survive, but in the winter, they live beneath these ice layers with minimal access to the air above. The frogs and turtles living in these bodies of water must also survive the frigid temperatures of the icy water. Frogs and turtles are ectotherms or cold-blooded animals, meaning their internal body temperature depends on the temperature of the environment around them. You can often see Eastern Painted Turtles sunning themselves on rocks and logs in the summertime – this is a turtle’s way of warming its body. Likewise, you can find frogs floating on the surface of ponds or sitting on lily pads, also using the warmth from the sun to warm their bodies. However, while living beneath an ice sheet, the body temperature of these species matches the temperature of the water, posing an additional challenge to winter survival. So how do these animals survive?

Closeup of an Eastern Painted Turtle

NPS Photo/ Sara Feldt

Turtles

Turtles will bury themselves in the mud at the bottom of ponds to stay as warm as possible in the absence of enough warming sunlight. Like humans, these turtles need oxygen to survive, but while buried in the mud beneath a layer of ice, they are not able to breathe air like we do. Instead they have adapted to be able to breathe under water through their rear ends. During the summer months, plants in the water add oxygen to the water. The turtles take this oxygen out of the water and into their body through the veins in their rear ends. When the turtle emerges from its hibernation-like state in the spring, they are especially slow moving. Have you ever had a sore muscle? Have you ever had an entire body of sore muscles? This kind of breathing is not as efficient as lung-breathing, so when the turtles emerge after the ice melts, their bodies feel like one big muscle cramp. If you see a turtle in the springtime, make sure to give it some space because it is probably tying to warm its body and wait for the muscle cramps to go away.

Green Frog lying in wait

NPS Photo/ J Goodman

Frogs

Many assume that frogs spend their winters as aquatic turtles do, buried beneath the mud. This is a common misconception, though. Frogs use their skin to breathe, so they would not be able to breathe if they were buried in the mud. Aquatic frogs enter a state of hibernation spending most of their time lying on top of the mud or slowly swimming around. The frog pumps a kind of anti-freeze through its body to protect individual cells, but then parts of the frog literally freeze solid. The frog essentially becomes a frogsicle. Its heart stops beating, it stops breathing, and as far as we know its brain also stops working. When the spring comes, though, the frogs hop back into action unharmed from their experiences in the winter.

Though the winter seems harsh for these animals, they are well adapted for survival in these intense conditions. If you find yourself ice skating on Eagle Lake in February, take a moment to appreciate the biological masterpiece of survival that lies below your feet.