After the April snow and cold, frogs arrive
The weather during the first week of April this year was a bit of an anomaly. For the most part, the winter was mild and months of temperatures above normal became normal. And where the first half of March produced mild temperatures, we looked like we were headed for an early spring.
Ironically, it was when we entered spring that we reverted to some cooling and more snow. April dawned and this trend continued for the first week. During this time we recorded more snow than we usually get for the entire month. And the cold lasted, near zero degrees on April 9 with plenty of chilly winds. April is extremely variable; in 2010 virtually no snow fell and in 2013 a record-setting nearly 51 inches occurred.
After living through a Northland winter, many local residents were disappointed with the return of this snow and cold. But like most happenings in nature, there is another side to this situation.
Thanks to April snows, especially if they tend to last in the subsequent cold, two natural phenomena that we do not appreciate are slowed or delayed. One is the fire season. When the snow melts and the dead grasses are exposed from under months of snow cover, they can dry and become a fire hazard, some years being extreme. Also of note, after the snow melts and warms, ticks that have been dormant all winter become active. April snows and cold also slow their activity.
To me, the greatest result of the April (and March) snow is in the snow itself, the moisture. These late-season snows tend to be wet. After the chilly and dormant season of winter, many critters are quick to take advantage of this moisture in the springtime of their lives.
Along with the snow and cold of the first week of April, we also experienced lengthening days by passing the threshold of 13 hours of daylight, expanding each day. Early migrants have been with us for a few weeks now and they make use of the melting snow that gave ample water in the vernal ponds. Canada geese, mallards, wood ducks, hooded mergansers and red-winged blackbirds are soon to arrive. Other songbirds that now appear, sparrows, juncos, robins, warblers, phoebes and swallows, find feeding is better near these newly-formed ponds.
But what I look and listen for mostly in mid-April is the reawakening and the return of frogs. Frogs are amphibians and as such, they are cold-blooded (ectotherms). This means that their body temperature, unlike ours, varies greatly and is about equal to that of their surroundings. They are unable to stay active in winter like birds and mammals. Instead, most go to a sheltered site where they use the protection of soil, leaves and even snow to be away from the cold that could harm them.
We have seven kinds of frogs and one toad in the Northland, collectively called anurans. Three of these, the leopard, mink and green frogs, bury themselves in the mud under ponds, swamps and lakes for winter. The other five — wood frog, chorus frog, spring peeper, gray tree frog and American toad — all winter on land. Some, especially the wood frog, are able to allow part of their body to actually freeze, but now in mid-April, they are able to thaw out.
These frogs breed at different times. Four are early spring (April, May), two are mid-spring (May, June) and two breed in summer (June, July, August). Earliest are the wood and chorus frogs, joined a little later by spring peepers and leopard frogs. In May, we'll hear the gray tree frogs and the toads. Mink and green frogs call on summer nights.
It is the early spring ones that seem to be eagerly waiting for the snow to melt and form vernal ponds where they deposit their eggs. Being amphibians, these frogs need to return to their aquatic origins each year for breeding. Though there are four frogs calling in April, as soon as they can, first are wood and chorus frogs.
Wood frogs are normally gray to brown, maybe even reddish brown, with a black patch behind the eyes. They are typically 2-3 inches long. Life is spent in the woods except for a couple of weeks in early spring (April) when they become aquatic and go to ponds to call, mate and lay eggs. Males call the females with clucking sounds that might remind us of ducks. Breeding is short and fast and usually completed by the end of this spring month.
Chorus frogs are only about 1 inch long and grayish, greenish-brown with stripes, our only striped frog. Also terrestrial, they go to vernal ponds as soon as they can to breed. Males attract females by clicking noises, often compared to us moving our thumb over the teeth of a comb. Though their season last a little longer, by June they are gone and disperse for the warmer weather.
Both frogs, as well as spring peepers, breed in vernal ponds that tend to be temporary and evaporate in summer. Under these conditions, they need to develop quickly through their tadpole stage. And so they call and breed in April ponds refurbished by the melting of these recent snows.
An adult chorus frog. Note the stripes on its small body. (Photo by Larry Weber)
Retired teacher Larry Weber is the author of several books, including “Butterflies of the North Woods,” “Spiders of the North Woods,” “Webwood” and “In a Patch of Goldenrods.” Contact him c/o email@example.com.