A popular saying in the olden days was that children should be seen and not heard. That definitely wouldn’t work for spring peepers.
An inch long at the most, they are seldom seen, even where they are most plentiful, in eastern and southern Ohio. Plus, they emit a shrill, piercing sound that can be heard for miles when it’s mating season, which usually happens at the end of February or the beginning of March, depending on where they are in the state.
The saying also wouldn’t work for a lot of people who welcome the spring peepers’ song as a sign that warmer weather is coming. Finally.
“To me, that’s the first sign of spring,” said Brian Banbury, who is the executive administrator of information and education for the ODNR Division of Wildlife but has been involved in herpetology most of his life.
Pack a punch
And once they start singing, spring peepers are hard to ignore.
“They’re small little frogs, not much bigger than the end of your thumb, but they pack a big punch volume-wise,” he said.
That’s thanks to the big sack made of flexible skin right below their chins. They fill up their lungs with air and push it back and forth through their vocal cords, then into the air sack.
“It’s like blowing a bubble with chewing gum,” Banbury said.
This takes a powerful contraction of their abdominal muscles, and a lot of energy considering they just woke up from a long winter’s nap.
Going into fall, peepers load up on insects, their main food item, then find some loose bark or leaf litter to tuck into. The time of hibernation is weather-dependent, but usually, it’s some time in November, Banbury said.
Their metabolism slows down and they go into a semi-conscious or even unconscious state. It doesn’t matter if temperatures get below zero; they move their glucose, or blood sugar, to their cells so they don’t freeze.
However, the water outside the cells can freeze, especially in their abdomens. Up to 40% of their body water can be frozen for up to 10 days, and this amazing little frog still survives.
In southern Ohio, spring peepers are considered “late winter” breeders, usually between the third week of February and the second week of March. In northern Ohio, that schedule is usually two weeks later, said herpetologist Jeff Davis, who lives in Butler County.
Davis works as a consultant to state and federal agencies, private companies and park districts, determining if there are any endangered species that might be affected by new construction. And he tries to ensure that suitable habitat for reptiles and amphibians remains after the road is finished or the power line installed.
If temperatures are below 50 degrees, cold-blooded spring peepers tend to stay put, Davis said. But when daytime highs reach about 55, and it begins to rain, that’s when they begin their migration to pools, ponds and nonflowing wetlands to mate.
Temperatures reached 60 degrees in southern Ohio March 11, and there was heavy rain. That night, “there were frogs and salamanders everywhere,” Davis said.
It’s not part of his job, but he couldn’t resist going to a Warren County wetland to see the mass migration. He estimates there were at least 5,000 spring peepers, plus other frogs and amphibians. He was glad to see that other people had also come to observe the overnight parade, including parents and kids.
“Spring peepers are popular because they’re harbingers of spring,” he said. “A lot of nature lovers know what they are and where they breed, so they come to watch them move into ponds and wetlands along with salamanders and other species. It’s a natural phenomenon.”
Male spring peepers arrive at the breeding sites a day or two before the females and immediately begin their loud, high-pitched call, appropriately dubbed the “advertisement call,” Davis said.
Although humans can’t hear the difference, female frogs are more attracted to males that sing with a slightly lower voice, indicating they have lived to the ripe old age of 2 or 3 and perhaps will contribute better genes to their offspring.
But the 1-year-olds whose voices haven’t changed can contribute, too. Known as “satellite males,” they stay safely out of sight of the older males, but can intercept a female hoping to meet the guy with the deeper voice.
When a female approaches, the male climbs on her back with his front legs secured under hers. She then jumps into the water with the male in tow, laying her eggs on submerged vegetation. When she releases an egg, the male fertilizes it. She then moves a centimeter or two and they repeat the process.
The female can lay anywhere between 200 and 1,000 eggs, Davis said. Several different males may fertilize one female’s eggs, helping to diversify the gene pool.
Speaking of pool, mating often takes place in vernal pools that fill up in the winter and spring and usually dry up some time in the fall. These pools have an advantage over ponds, rivers and lakes because they don’t have fish to eat the tadpoles. Vernal pools are also used by wood frogs, cricket frogs, spotted salamanders, Jefferson salamanders and fairy shrimp for breeding, Banbury said.
Spring peepers don’t just have a mating call. They also have a similar, but more stuttering call that they use when they see other males, called the “encounter call.”
Nor is their peeping restricted to spring. They have something named the “rain call” which they emit on days of high humidity, or when a storm is coming, well into summer. Mating can last into the summer as well.
“It’s a survival strategy to get as many young as possible,” Banbury said.
The first tadpoles to hatch in a vernal pool will have the first shot at the food. If the pool dries up early, as it does some years, the microscopic critters the tadpoles rely on for food will disappear.
“Or the opposite could happen,” he said. “If there’s a long cold snap, the first group can perish. If you have babies stretched out over the spring, there’s more chance that some will make it.”
Exactly when spring peepers change from tadpoles into frogs is “kind of left up to nature,” Banbury said.
If conditions are good, they’ll remain tadpoles longer so they will be healthier and more robust when it comes time to make the change. On the other hand, if there are drought conditions and the vernal pool starts to disappear, they speed up the transformation process.
Davis said spring peepers are pretty sparse in Northwest Ohio, remaining in woodlands that are too wet to farm. Where they do occur in higher numbers, mostly in eastern and southern counties, spring peepers “have the highest density populations of any amphibian species,” he said.
Still, once those mass migrations are done, the little frogs are rarely seen. Their toes have sticky pads that allow them to climb trees and shrubs to find insects, but that’s usually done at night. They tend to spend most days on the ground, hiding beneath leaf litter.
Davis is one of the authors of Amphibians of Ohio, published in 2013, and Reptiles of Ohio, which will come out in May. His job as a consultant takes a lot of time and travel, so it’s not like he has hours to kill. Yet he stayed up all night to watch that mass migration in Warren County.
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