Jerry and Jody Zamirowski of Glen Ellyn have observed some unusual sights in the decades they've spent volunteering to monitor animals for the DuPage County Forest Preserve District and the Morton Arboretum in Lisle.
They've spied rare bird and dragonfly species in detailing animal behavior patterns and populations. They've also observed some frog species experience double mating seasons this year due to our early spring.
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But this week, while out with his wife, Jerry spotted a bullfrog at Hidden Lake Forest Preserve near Downers Grove. Quickly, he realized he'd found something amazing.
"I saw it with my binoculars and realized there wasn't algae or anything on it. It was just bright blue!" Zamirowski said.
The bullfrog possesses a rare genetic mutation that prevents its chromatophores -- cells in amphibians, reptiles and other animals that contain pigment and reflect light -- from producing yellow pigment, said DuPage Forest Preserve ecologist Dan Thompson.
"My basic understanding is that frogs are one of many species capable of changing their coloration, which is a mechanism to avoid predation by blending in the background of their natural setting," Thompson said.
"They are trying to mimic that green color, since they are frequently out in the marsh. Some green frogs can be brown to blend in with rocks, or the gray tree frog can appear to blend on a tree covered with lichens.
"But this may be a situation where it was not born with yellow pigmentation. Everyone knows if you mix blue and yellow, you get green. This guy is trying to be green, but if he's lacking the ability to produce that yellow pigment."
Zamirowski was able to snap a photo of the blue frog before it disappeared into the lake. That was important, he said, because he didn't know if he'd ever make such a find again.
Some of his research tells Zamirowski blue bullfrogs are about one in a million. Thompson said he's unsure of exact statistics but is certain the frog is "exceptionally rare."
"It's almost like finding a piece of a meteor," Zamirowski said.
He did not attempt to catch the rare frog, as it is illegal to take animals from forest preserve grounds. Plus, the frog will fare best in the wild.
Instead, Zamirowski and his wife are simply happy when their years of nature monitoring pay off with these unexpected surprises.
"We've been doing it so long, we don't chase the rarities anymore," he said, quipping, "Now they come to us."
Frog: 'It's almost like finding a piece of a meteor'