This bullfrog is blue due to a pigment mutation on the cellular level. It was spotted in a central Maine pond. Credit: Courtesy of Gretchen Gordon Audet

Green frogs and bullfrogs are common sights in freshwater ponds and wetlands around the state. But every so often, a frog that would be green is blue.

This is not a sad frog. Rather, it’s a color mutation known as axanthic, and is quite rare in the amphibian world.

Green-colored frogs get their color from two pigments — blue and yellow, according to Derek Yorks, wildlife biologist in reptiles, amphibians and turtles with the Maine Department of Inland Fisheries and Wildlife. When the yellow pigment is lacking, the frog is blue.

Gretchen Gordon Audet has one living in her central Maine pond and knows it is something special.

“It’s incredibly rare,” Yorks said. “We typically get reports of just one a year [and] so far this year we have gotten two.”

In addition to Audet’s frog, a blue frog was spotted this week in southern Maine. Yorks said these are lucky sightings.

“I have seen four blue frogs in my life,” Yorks said. “Three in one year and that was a banner year.”

Griffin Dill, integrated pest management specialist with University of Maine Cooperative Extension, said he’s seen them a couple of times.

“This is a relatively rare occurrence,” he said. “But it does tend to be more common in the northern areas.”

It’s the same sort of pigment mutation that creates blue lobsters like the one caught off the coast of Portland last month, according to Dill.

“We have gotten used to seeing different colored lobsters and we see a handful of those every year,” Dill said. “The frogs are a bit more rare.”

In Maine both green frogs and bullfrogs can exhibit the mutation.

Audet’s blue frog is a bullfrog and she said she has reported it to the Maine Herpetological Society.

“According to them [blue frogs] are very rare with only one reported as being seen each year,” Audet said. “It is very interesting, to say the least.”

The color mutation can turn the entire frog, or just part of it, blue.

“Sometimes you see a frog and its body’s blue and the legs are green,” Yorks said. “More rarely you will see one lacking the blue pigment and it will be yellow.”

The mutation is completely random and, according to Yorks, not triggered by any environmental conditions. It’s not the only color mutation among amphibians.

“The red backed salamander is one that practically every person in Maine has under a log in the backyard,” Yorks said. “It’s brownish with a wide, red stripe on its back and sometimes you get one that is entirely red.”

That mutation is called anerythristic.

While rare, it is possible to spot oddly pigmented amphibians when you know where to look, according to Yorks.

Dill’s blue frog sighting was near Pushaw Stream in Old Town.

“These color mutations do happen all the time,” Yorks said. “If you spend a lot of time in places with a lot of frogs, you will see one eventually.”

Audet is keeping an eye out for her blue bullfrog.

“I haven’t seen him for a couple of weeks,” she said. “Hopefully he’s still around.”

Julia Bayly

Julia Bayly is a reporter at the Bangor Daily News with a regular bi-weekly column. Julia has been a freelance travel writer/photographer since 2000.