The gray tree frog is far from the mundane color of its name. They can range from gray and green to brown to mimic lichen, a symbiotic partnership between fungus and algae that commonly covers tree bark. Its scientific name also includes “versicolor”, which means “variable color” in Latin, hinting at the frog’s color versatility. The gray tree frog’s bumpy skin changes color depending on the time of day and temperature! It has a lighter coloration during the daylight hours but morphs darker at night and in colder temperatures. This impressive adaptation is because of ‘chromatophores’, cells that expand and contract to allow melanin (pigment) into the skin.
Gray tree frogs can be found locally, thriving in New England as they can survive the harsh winters and freezing temperatures with ease through another unique adaptation. As temperatures plummet, gray tree frogs rely on their abnormally high amounts of glycerol, a naturally occurring alcohol, to coat their cells. The glycerol acts as an antifreeze, allowing their heartbeat to slow and breathing to stop. This adaptation prevents ice crystals from forming, essentially “freezing” themselves for their long winter hibernation. As spring emerges, the sleepy frog thaws out in its arboreal hideaway, its metabolic processes return to a regular rate, and the gray tree frog is ready for the spring mating season!
Gray tree frogs and other frogs are essential in conservation efforts as they are often indicators of environmental health. At Mystic Aquarium, we work to conserve frogs by monitoring chytrid fungus. This fungus has caused dozens of frog species to become extinct by infecting the skin of frogs and thickening it. Because frogs absorb water, oxygen, and nutrients through their skin, this can lead to their death. Mystic Aquarium monitors the spread of chytrid through one of its Citizen Science Programs. In this program, our local community can learn how to swab local frogs and other amphibians, and the collected sample is sent to a lab to test for the fungus.