Springtime is the best time. In terms of phenology, so much is happening seemingly all at once that it's as if the unfolding events are too much for our senses to completely absorb.
Although it might appear that spring has sprung just like that, for most everything, such as the swelling of tree buds to full leaf-out, "there is a season and a time for every matter ..."
If ever there were creatures that invoke the ephemeral spirit and renewal of spring, then surely these creatures would be, among others, the anurans, or better known as frogs and toads. These fascinating and delightful animals reappear each season in a predictable and fairly sequential order, depending upon the particular species and local environmental conditions.
In total, 14 species of frogs and toads call Minnesota's wetlands and waterways home. All of them lay eggs that hatch in the water and subsequently become tadpoles - those fish-like, gilled creatures that undergo the amazing transformation, or metamorphosis as it's called, from tadpole to frog or toad. At this writing, gray tree frogs are the dominant voice of the nighttime wetlands, but it wasn't long ago that their calls were absent.
The first frog to emerge and begin vocalizing here in northern Minnesota is the wood frog. Their breeding call, often described as "duck-like," sounds somewhat like the feeding call of mallard ducks. These common frogs have recently completed their brief breeding season and soon, if not already, wood frog tadpoles will be swimming, feeding and developing in their seasonal, forest wetlands.
Following wood frogs, and often simultaneously, are the western chorus frogs, sometimes called boreal chorus frogs. These tiny frogs, not much longer than an inch, are indeed small but are incredibly loud for their size. Their breeding trill-like call is described as sounding like a thumb drawn across the teeth of a hard plastic comb. This striped frog is classified as a species of tree frog.
Performing right on the heels of wood frogs and chorus frogs, is a favorite of mine - the spring peeper. Peepers are about the size of chorus frogs and, as their name suggests, their calls sound like extremely high-pitched peeps. As well, their music has also been described as akin to "sleigh bells." If ever you are fortunate enough to find yourself at the edge of a wetland teeming with vociferous spring peepers, you might have to cover your ears. Such cacophony can literally hurt your ears.
In the mix of these three aforementioned species, one can also tune into the northern leopard frog. Perhaps no other frog in Minnesota is more evenly distributed or more recognizable than the green colored, sometimes brownish, leopard frog. A rather large frog, sometimes exceeding 3½ inches, leopard frogs are easily identified both audibly and visually. The male's breeding call is described as having a snore-like quality that lasts surprisingly long, usually several seconds in duration, and ends with a series of "chuck" sounds.
Other favorite night calls, usually beginning in late May and into June, is the bird-like trills of the American toad and gray tree frog. These pleasant songs are sung by male toads and tree frogs during warm spring nights.
American toads, about the size of leopard frogs, but generally larger in circumference than leopard frogs, are squat, short limbed anurans that hop rather than leap like frogs do. And contrary to some accounts, the warty skin of toads does not cause warts to develop on people. Such skin-type is simply an adaptation to dry conditions.
Gray tree frogs sometimes call while sitting in the branches of trees and shrubs, but usually sing from the edges of wetlands near or within forests and woodlands. The suction cup toes of these well adapted arboreal frogs help them grip onto almost any surface as they vocalize or sit and wait for prey. It's common to find gray tree frogs clinging to glass windows at night as they hunt.
Other frogs of northern Minnesota include the lesser known green frog and mink frog. Green frogs are rather large frogs, slightly larger than leopard frogs and resembling smaller versions of the much bigger bullfrog. Often associated with permanent bodies of water such as lakes, especially bays with plenty of emergent vegetation such as lily pads and bulrush, the voice of the green frog is unmistakable. Think of a loose banjo string being plucked and you get a good idea of what a green frog sounds like.
According to the Minnesota DNR, the voice of mink frogs is described as a "rapid cut, cut, cut resembling a hammer striking wood; when mink frogs call in chorus it sounds like horses' hooves on a cobblestone road." These attractive frogs look similar to green frogs and will be found in the same habitats as green frogs. The name "mink" was given to the frog because of the musky, mink-like odor its skin produces when handled.
Other frogs and toads that occur in Minnesota include the largest North American frog, the bullfrog, in addition to the pickerel frog, Cope's gray tree frog, and northern cricket frog. There are also two other toads, the Canadian toad and Great Plains toad.
Indeed, whether it's the snores of leopard frogs, the plunks of green frogs, the low "rumm, rumm, rumm" notes of bullfrogs, or the beautiful trills of American toads, what would our springs and summers be like without them?
I can no sooner imagine the daytime without birdsongs as I can imagine the night without the soothing songs of frogs and toads as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org