Vernal pools attract amphibians and many different species

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wood frog
Wood frogs are among the earliest frogs to breed in the spring, and this male was using the vernal pool at the University of Mount Union’s nature center for that purpose. Characterized by black markings around the eyes that resembles a mask, and a white line above their lips, wood frogs have a mating call that is more of a quack.

“Build it and they will come” has taken on new meaning at the University of Mount Union’s Huston-Brumbaugh Nature Center. The vernal pool that was constructed five years ago has attracted frogs, ducks, snakes, newts, and intriguing invertebrates like fingernail clams and water fleas, though no fairy shrimp just yet.

But it has also attracted humans who happen to be hiking along the boardwalk, or who come specifically to see what’s going on in the pool. “The longer they look in the water, they’ll spot something and say, ‘What the heck is that?’ and get out their phones to take pictures,” said Chris Stanton, a biology professor at Mount Union and director of the nature center. “That’s really exciting to see.”

University of Mount Union vernal pool tour
Chris Stanton, biology professor and director of the Huston-Brumbaugh Nature Center, tells visitors how frogs and other amphibians use vernal pools for breeding. The center’s pool, built five years ago, also provides habitat for ducks, snakes, newts and thousands of invertebrates. “They’re all part of the food chain,” Stanton said. (Barbara Mudrak photos)

Vernal pool

A vernal pool is different from a pond because it fills up in the spring and dries up by fall. That prevents fish from taking up permanent residence, so amphibians and other species can use the pool for breeding without fish consuming their young.

Stanton led vernal pool tours at the nature center the third weekend in March. The spring peepers and wood frogs were pretty quiet Saturday night due to chilly temperatures, but on a sunny Sunday afternoon, they cranked up the decibels.

Marge and John Versiackas, of Stark County’s Washington Township, attended the programs both days. “We’re thinking of putting in a vernal pool on our property,” Marge said.

Jim Hoover, Julie Stephens and sons Gage, 14, and Trystin, 13, both students at Alliance Middle School, were there for the frog concert Sunday. The boys were recruited to help Stanton scoop critters out of the pool and put them in porcelain pans for closer inspection.

The first scoop captured a predaceous diving beetle, which just looks like a fat bug at first glance, but has some hidden talents.

“They get a bubble of air and hold it under their wings,” Stanton told visitors. “That lets them scuba dive for a while, then they have to come to the surface and get another one.”

Oh, and the larvae of these beetles will eat things many times their size by injecting a liquid that dissolves the prey, he added. Another scoop brought up aquatic worms that look like little pieces of thread. They eat bacteria, sediment, dead leaves … stuff you wouldn’t think was edible.

But as the material goes through the worms’ intestines, the nutrients in it are condensed. This actually provides good food for frog larvae and tadpoles.

Meanwhile, the worms and other invertebrates provide food for adult frogs, and the mallards and wood ducks that visit the pool. The ducks filter water through their beaks, but the invertebrates remain and are swallowed, Stanton said.

Chris Stanton
Chris Stanton scoops invertebrates and other creatures from the vernal pool at the University of Mount Union’s nature center for visitors to examine. Though there were plenty of wood frogs available, the few spring peepers present on that March weekend proved to be loud but elusive.

Frogs

All very interesting, but the main attraction on the tours were definitely the frogs, which had come to the vernal pool only a week or two before. There were just a few spring peepers, whose small size made them mostly invisible under water. However, their calls to attract females were so loud they left the humans’ ears ringing.

The wood frogs’ mating call sounds like ducks quacking. They almost equalled the peepers in volume, mostly because of their numbers.

Dozens of dark-brown males could be seen floating leisurely on the surface, or competing for the attention of the more pinkish-colored females. “I think it’s pretty cool to see how they interact with each other,” Trystin said.

The females lay eggs near the surface on sticks or vegetation, after which males fertilize them. There can be hundreds of eggs in each mass, which is then covered with a gelatin-like substance that protects them from water molds and “doesn’t taste good to predators,” Stanton said.

When the eggs hatch, the resulting tadpoles eat microorganisms and vegetation on the bottom of the pool. After about two months, they morph into miniature replicas of adult frogs and leave the pool to spend the rest of their lives in the woods.

Vernal pools aren’t only good for propagation, but also for energy transfer — as in food energy.

“The frogs lay eggs, then the tadpoles consume food resources in the pool,” said Adam Zorn, program manager for the nature center. “When they become frogs, the energy is transferred to the surrounding land.”

In other words, the adult frog could be eaten by a snake, the snake could be eaten by a hawk, and so on.

The location of the pool was an easy choice, said Zorn, who helped with the construction. It was always a wet spot in spring, but the water was only 1 or 2 inches deep. It would often dry up within two weeks, not long enough to support amphibian breeding, or much of anything else.

An excavator dug the pool to depths of 1, 2 or 3 feet “so it wouldn’t look like a big cereal bowl,” Zorn said.

The bottom of the pool is mostly clay or silt loam, perfect for holding water, but the topsoil was put back “because it holds tree seeds and other nutrients,” he said.

Zorn then brought in piles of dead leaves, and some sticks and logs for good measure. The university recently purchased some land adjoining the nature center that contains four vernal pools. Stanton’s biology students monitor the water quality of the pools and will eventually do surveys to see what species are using them.

For instance, after the wood frogs and spring peepers are finished breeding, they will move out to the surrounding woods and American toads and gray tree frogs will move into the pool. “It will sound completely different in a month or two,” Stanton said.

Newts

The handbook Ohio’s Hidden Wonders says in addition to frogs, vernal pools are used by other amphibians, especially mole salamanders. None have been seen yet in the nature center’s pool, but there have been some red-spotted newts.

They are related to salamanders, and are the only newts native to Ohio. Their red spots are designed to warn predators that they won’t taste good, Stanton said.

According to the handbook, vernal pools are used by Eastern garter snakes, Eastern ribbon snakes and Northern water snakes, which are all comfortable in water and feed on amphibians and insects.

Five species of turtles, including Eastern box and Eastern painted turtles, often hang out at vernal pools. Scientists say North America is losing more than three percent of its amphibians each year, with even greater losses in other parts of the world. Reasons include loss of wetland habitat, a fungus that is fatal to many frogs, a parasite that causes deformities, plus other factors.

Vernal pools can help them repopulate. Zorn and Stanton say many nature centers and metroparks in Ohio are installing vernal pools, and that raises public awareness. There are websites with plans for constructing vernal pools, which can also be dug by hand.

Vernal Poolooza, a website of the Ohio Wetlands Association, has online programs every third Friday at 11:30 a.m. “The message is getting out,” said Stanton. “A lot of people know about vernal pools now, and some are building them on their own property. They don’t look like much, but they’re an important habitat.”

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