Nature Notes: Spring Peepers
By Ed Robinson
Humans are funny creatures. As we age, our memories are no longer razor sharp, so we may find ourselves standing in the kitchen wondering what it was we intended to fetch. We hunt for our reading glasses only to find them on our head! On the other hand, we have lasting memories for pleasant things like our first kiss, a great glass of red wine or a stunning vacation spot. I’ll wager that you never will forget certain sounds from your youth, maybe the Good Humor ice cream truck coming down the road or the opening bars of a favorite song like the Beach Boys’ “Good Vibrations.”
Sounds of nature can also plant themselves firmly in our minds, like the haunting call from the first V-shaped flock of migrating geese winging south. In the same category is the high-pitched tinkling of the spring peeper, normally heard in a cacophony of sound from hundreds of voices. It is a good bet that you would recognize that sound instantly even if you have never seen one of the diminutive frogs. For creatures that weigh just a fraction of an ounce they have an amazing ability to sing one of the most distinctive sounds of spring, and they do so long and loud.
The tiny Psedoacris crucifer is mostly a creature of the eastern US, found from southern Canada down to the Gulf Coast states. There are two subspecies, but in Maine you will find the northern spring peeper. In fact, you might not actually find one at all because they are so small and so reclusive, but they will gladly share their bell-like call with you, hour after hour for many weeks from March into June. It will not be long after this article appears that you can listen to the evening chorus in a nearby vernal pool, swamp or quiet stream. Spring peepers are distinctive members of a group known as the chorus frogs, a perfect name given their behavior.
An adult male is under one inch in length, the female about 40 percent larger. Their smooth skin varies from light tan to dark brown, light green to gray, in part because they have a partial ability to change color to blend into their wetland environment. Their bellies are light colored, and there are dark bands on the legs and face. Many of the peepers display a dark cross-shaped figure on their backs, the source of the Latin name “crucifer,” the cross-bearer. Like most amphibians, the toes are equipped with special flat pads that provide wonderful gripping ability so the animal can climb all kinds of surfaces. While peepers prefer to remain among vegetation along the water’s edge, they are capable of swimming thanks to webbed hind feet.
Peepers hibernate in winter, having found their way into resting spots in soft mud, leaf litter, rotting logs or holes in the ground. Their metabolism drops to a minimal level of activity, allowing the creatures to survive months with no food intake. The peepers produce glucose that acts like antifreeze to displace water in their cells, allowing the cells to freeze without damage from ice crystals, assisting survival in temperatures down to 20 degrees F. The glucose and glycogen are also used as energy sources to sustain life all winter. When cold weather eases, the peepers have run out of sugar so they become active early in spring, sometimes before ice out. I have walked the trail at Long Reach Preserve with the accompaniment of peepers even though the vernal pools were mostly frozen over.
Once the peepers are active, they are focused on two things, eating and mating. Peepers eat a variety of foods, with their tadpoles consuming tiny eggs, algae and microbes in the water and adults eating a range of beetles, flies, ants and spiders. As the light of day begins to fade, males gather in numbers up to the hundreds to broadcast their mating calls at surprising volume given the size of the creature. As with other frogs, peepers are able to inflate a special sac in their throats to a size that rivals their bodies, expelling the air over their vocal cords at a rapid rate, up to 20 times per minute. Females are attracted to the males who can sing the fastest and the loudest, generally the most robust males in the chorus. Some males apparently choose not to sing, but lie in wait near dominant males in hopes of intercepting a willing female.
Once a female has selected her beau, she touches him to indicate a willingness to breed. The smaller male hops astride the female’s back and rides around with her until she begins laying up to 1,200 eggs. The male ejects his sperm as the eggs are deposited on aquatic vegetation, with fertilization occurring quickly. Depending upon the temperatures, eggs may hatch anywhere from two to 14 days after deposition. The peepers prosper in waters that do not contain fish, allowing a higher survival rate of their offspring. The tiny tadpoles are equipped with gills for breathing in the water but within three months they lose their tails and begin using their lungs as they move onto land for the rest of their short lives, less than four years.
In the complex food chain of their environment, peepers play a role in controlling insect populations and they are prey for salamanders, snakes, skunks, raccoons and a range of birds. Fortunately, the peepers are prolific breeders and while it is difficult to count such reclusive creatures, their population numbers seem stable thanks to efforts to preserve sensitive wetland environments. Clean air and water legislation also has been important to protecting these valuable habitats, by reducing direct water pollution and acid rain.
As the Farmer’s Almanac puts it, you can be sure that “spring has finally sprung” when you hear the peal of the spring peepers. On the first warm evening of spring, take a stroll to HHLT preserves at Long Reach, Houghton Graves Park, Curtis Farm and Little Ponds, or walk the Hackett and Minot Trails where there is a lovely vernal pool. Enjoy the night music!