Ruth Smith: Our hidden ventriloquist

  • Gray tree frogs are usually light gray, but they also can change into shades of white, green and black, depending on the scenario. AP

For the Monitor
Published: 6/7/2020 6:29:41 PM

Early summer is upon us and the spring soundtrack of bird songs has begun to diminish. Courtship refrains are no longer the birds’ priorities. As parents, many are now focused on feeding young, delivering insects to gaping mouths every few minutes. It’s hard to sing with a caterpillar or moth in your mouth! But new performers join the scene and the sounds of summer include numerous insects and different frog species, including the gray tree frog.

Their name tells a lot about their appearance and habitat. As adults they do live in trees and except for the streak of orange on the inside of their back legs, they are mostly gray (except when they aren’t).

Sticky toe pads enable them to climb up vertical surfaces. They are miniature, 2.5-inch acrobats as well, taking flying leaps from branch to branch or lunging from an arboreal perch in pursuit of an insect meal.

Their color takes a bit more explanation. Their scientific name Hyla versicolor provides even more of a clue about their color – it’s versatile and changeable. While most often light gray, like the bark of an old sugar maple tree, depending on temperature, humidity and light intensity, these frogs can change from nearly white to green or almost black. As it gets colder, they tend to get darker. This may help them blend in with the dark as night falls.

Color variations also help distinguish the sexes. The male has a gray to black throat while the female’s throat is light gray or nearly white. Another way to tell them apart is that only the male sings. When he does, his dark throat expands like a giant bubble, filling his vocal sac with air to amplify the sound.

His vocalization, a loud explosive trill, can carry a great distance, making him hard to locate and giving him the reputation of a ventriloquist. His call and location in trees often leads people to mistake Hyla for a bird. They are also frequently misnamed tree toads because of their warty looking skin, but make no mistake – this amazing singer is a fabulous frog.

Like nearly all frogs, they lay their eggs in water, so are found in mixed woodlands where vernal pools, ponds or wetlands are close by. The trill is a mating call, usually sung before migrating to the ponds. Females choose a mate based on his singing ability. When they rendezvous at the pond, the female lays her eggs in clumps of 10-40, attaching them to underwater vegetation. She will lay up to 2,000 eggs each season. The eggs hatch within 2 to 5 days, if conditions are right.

Tadpoles, which can be seen from May through July, start out light yellow but turn to olive green with a brick-red tail. Their skin produces toxic secretions and it is thought that the red tail may be a warning to predators. After 1 to 2 months, going through the incredible metamorphic cycle of growing legs, absorbing the tail, gaining lungs, losing gills, moving eyes from the side of their head to the front, they will come out on land. At this point they are bright green and head for the tops of trees where they blend in with leaves.

It takes at least two years for the frogs to reach sexual maturity. During that time they will migrate from trees back to the ground where they will spend the winter beneath leaves, rocks or in small mammal burrows. Their body can drop below freezing without being damaged due to glycerol and glucose in their system which serve as an antifreeze.

As mature adults, their migration between trees and water provides the best opportunity for us to encounter them. Watch your windows in the evening if you have lights on that attract insects. Their sticky toe pads may help them scale a window as well as Spider-Man. Sometimes I find them on a stone wall, disguised as a clump of lichen. Seeing them is always a treat, but listening to them on moist evenings or before a late afternoon thunderstorm brings back fond memories of childhood summers. I hope you take time to listen for gray tree frog songs and create some of your own fond summer memories.


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