Eastern Gray Treefrog
| Scientific Name | Hyla versicolor |
| Survival Strategy | Brumation / Freeze-tolerance |
| Begin Brumation | Mid fall |
| End Brumation | Early Spring |
| Conservation status | Least Concern |
Spring
Treefrogs emerge from brumation in early spring, with the breeding season running from late April to early July, as long as the air temperature stays above 15°C (60°F). The female lays 1000 to 2000 eggs in still water ponds, and the pea-sized tadpoles hatch three to seven days later.
Summer
Metamorphosis occurs in about six to eight weeks, after which the young frogs look like miniature versions of adult treefrogs. Gray treefrogs are nocturnal and spend their days hiding from predators and sheltered from the sun. At night they come out to feed on insects and small invertebrates.
Fall
As the cooler weather of late fall sets in, treefrogs move to secluded spots to spend the winter (hibernaculum). Their liver will begin to produce the antifreeze that will keep the low temperatures from destroying their cells.
Winter
Grey treefrogs are terrestrial. Unlike aquatic frogs that overwinter in the cold water of ice-covered lakes and ponds, treefrogs spend the winter months on land. They survive the cold weather frozen solid, in trees, under logs, and leaf litter.
Behavior
Mating Calls
After ending brumation, the loud trill of the gray treefrog’s mating call fills the evening air. Although more common in the breeding season, gray treefrogs continue calling on humid nights all summer. Male gray treefrogs create their call by pushing air over their vocal cords from their inflated vocal sac.
Physiology
Freezing
As the air temperature drops in the fall, the gray treefrog’s liver converts glycogen into glycerol, a natural antifreeze. When they start brumation (hibernation for cold-blooded animals), a treefrog’s cells fill with glycerol.
The glycerol prevents the water inside the cell from expanding as it turns into ice crystals and destroys the cell. Anyone who has left a can of soda in the freezer too long is familiar with the process. The water between the treefrog’s cells is allowed to freeze safely. Over 80% of the gray treefrog’s body freezes, their eyes become opaque, and breathing, heartbeats, and brain activity temporarily stop.
Color Change
A gray treefrog can quickly change color by manipulating color-producing cells (chromatophores) in their skin that they control with hormones and neurons. The color of a frog’s skin results from blending three layers of chromatophores, each with a different color profile. The layer closest to the skin surface contains yellow and red pigments. The middle layer holds nanoscale iridescent crystals that act like selective mirrors. The deepest layer features black pigments. Treefrogs can change the shape of these color-producing cells, which rearranges the location of the pigments. When the pigments are corralled into one spot, the color lightens. When the pigments spread throughout the cell, the color darkens.
Frogs adjust their color to blend with their surroundings or help control their body temperature. Treefrogs will feature darker, more heat-absorbent pigments during cooler weather. As the air warms, frogs change to lighter colors that absorb less heat.
Climbing Gear
The incredible climbing ability of the gray treefrog comes from the large toepads on their feet. Each toepad produces mucus that works as a temporary adhesive (think “sticky notes”), allowing this insectivore to climb trees, walls, and even glass windows.
Toxic Skin
The skin of the eastern gray treefrog secretes a toxin that may protect it from some (but not all) of its predators. The toxin will also create an uncomfortable reaction in human eyes and lips. If you handle
Diet
The gray treefrogs are nocturnal insectivores. Their diet consists of invertebrates such as moths, spiders, crickets, and beetles.
Lifespan and Mortality
The average lifespan of an eastern gray treefrog is seven to nine years.
Predators
Predators include diving beetles, fish, salamanders, larger frogs, turtles, herons, raccoons, and striped skunks.
Climate Vulnerability
A University of Missouri study found that increasing temperatures and climate variability may affect the mating calls of gray treefrogs. There is no evidence that these changes in calls hinder mate selection.
Never stop learning
Etymology: The gray treefrog’s scientific name is Hyla versicolor. “Hyla” comes from Greek and means “belonging to the woods,” and “versicolor” comes from Latin for “variable color.”
First Nations: The Ojibwe word for treefrog is “agoozimakakii na.”