As spring days become longer and the temperatures warm, we begin to see a few animals that we haven’t seen in months. Specifically, we begin to see local amphibians as they awake from their winter slumber and begin to move.
They may not be the easiest to spot, but they are among some of the most fascinating of our wildlife species.
Amphibians, such as salamanders and frogs, have inhabited north Iowa since the last ice age ended more than 10,000 years ago. Many scientists believe that as the glaciers retreated, amphibians moved into the melt waters left behind. They thrived there thanks to ideal environmental conditions and few predatory fish.
Today, amphibians can be found throughout the state, wherever there are ponds, lakes, streams, rivers, marshes, or even wet drainage ditches. That’s because they breed underwater and their shell-less eggs need to be placed underwater so they stay moist. After they hatch, amphibians spend their early lives in the water, breathing with gills.
As they mature, most lose their gills and spend their adult lives living on land, breathing with primitive lungs or absorbing oxygen through their skin. Without scales, though, they still need to be near water or moist areas to keep from becoming too dry. This need to live both in the water and on land makes amphibians a very unique class of animals.
Amphibians are also cold-blooded, which means that their body temperature changes with the air temperature. That’s why we don’t see them during the winter.
During the frigid, winter months, salamanders and frogs are comfortably hibernating in protected, relatively warm, places. Many frogs will hibernate in the water or the mud at the bottom of a pond, safely insulated from the winter air by mud, water, ice, and snow.
Other frogs and salamanders will hibernate underground, below the frost line or in a similarly sheltered location such as a large leaf pile. During hibernation, the metabolism of amphibians slows down so much that they need no food and very little oxygen. They are able to survive all winter in these locations.
Now that spring is here and the temperatures are warming, our local amphibians are waking up and beginning to move around once again. Their first order of business is finding a mate. Actually, some of them have already mated, in the water, under the ice.
The rest spend the spring looking for mates, which is one reason why we tend to see and hear them more in the spring than at any other time of the year. Salamanders can be seen walking around in search of a mate and male frogs heard attempting to woo females with their courtship calls.
Usually, the first frogs heard in the springtime are the chorus frogs, tiny little frogs (barely over an inch long) with loud voices. They begin to call soon after the snow melts, usually from grassy areas with shallow water.
Their calls sound like someone running their thumb over the teeth of a comb. Although most species of frogs call after dark, chorus frogs often can be heard throughout the day as well.
In the spring, leopard frogs begin calling. Their calls sound like someone running their fingers over a balloon. They also sometimes produce a low chuckling sound. The high, steady hum of toads can be heard as they too begin searching for a mate. If you hear a short, high-pitched trill, you’re most likely hearing the call of a gray tree frog. They too begin calling in the spring, but continue to call into the summer.
Later, frogs will stop calling as their mating seasons end and salamanders will be hard to find as the heat of summer forces them to stay hidden once again. Spring is definitely the most active time of year for local amphibians. So, be sure to watch and listen for these amazing creatures. They truly are wonderful signs of spring.