Rare blue bullfrogs spotted in Iowa

(Photo courtesy of Iowa DNR)

Have you ever seen a blue bullfrog in Iowa?

The Iowa DNR had reports of sightings from southern Iowa late last month.

There are several genes that make a frog green or brown, and these genes result in various structures being created in the frog’s skin layers. The lower skin layer reflects light, and as that light passes through the upper skin layers, various wavelengths are filtered out so the frog looks green or greenish-brown.

In some frogs, a genetic mutation removes some of the skin’s ability to produce yellow pigment. That can filter out certain wavelengths, resulting in a blue bullfrog. Leopard frogs can also be affected by this.

These blue-colored frogs are thought to be a rare sight in the wild because their odd coloring makes them much more visible to predators. So they get eaten faster than their normal green- to brown-colored relatives that use their coloration to blend into the vegetation and mud in Iowa ponds and lakes.

This is at least the fifth blue bullfrog in Iowa that we’ve heard of, with one DNR staffer remembering another blue bullfrog from the same southern county about 20 years ago. We had another send photos of one from western Iowa just last year.

The western Iowa frog isn’t as vibrantly blue as the one from southern Iowa that the DNR saw this year. The western Iowa frog looks more gray than blue, but the 2017 frog is a clear, bright blue that stands out much more vividly.

Two other blue frogs were also reported in southern Iowa.

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