The beauty and the beast; or, a tale of two moles

The Beauty

Technically, golden moles are not true moles—they are more closely related to tenrecs than they are to true moles—but golden moles are small, burrowing, insect-eating mammals that, with their streamlined heads and powerful digging claws, have converged to look a lot like true moles.

With at least one key difference: golden moles shine. They shimmer. They iridesce.

Juliana's golden mole. Photo from ARKive.

Juliana’s golden mole. It’s a bit hard to see the iridescence in photographs, but it’s there. Photo from ARKive.

The hairs on a golden mole reflect light in such a way to give the animal a sheen, ranging in color from gold to green to purple. In the museum where I work, we have some preserved specimens of golden moles, and they are remarkable to see: their fur shines and shimmers like the coat of a child’s stuffed toy unicorn.

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The many (and changeable) colors of the Pacific tree frog

We spend a lot of time looking for junco nests in my field work, which means we spend a lot of time looking at the ground, which means we see a lot of these little guys:

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Pacific tree frogs come in two main flavors: brown and green.

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Some frogs stay the same color for their entire lives, but some can change from brown to green, or vice versa, depending on whether the background is dark (brown) or light (green). You can see how this might be handy if you want to blend in with the background.

You can't see me!

You can’t see me!

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Ghost junco

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Isn’t he beautiful? He was caught in the hills in Marin County, not all that far from me, and kept in captivity until he died in 1931.

You might think he’s purely colorless at first glance, but he isn’t. He’s more blue-silver than white, an incredible color to come shining out of a drawer of junco specimens when you’ve just spent the last few weeks measuring the same brown-and-black birds over and over. When you look close you find that hidden in those pale feathers are the whispers of normal junco coloration.

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Red finch, orange finch, yellow finch

In general, we understand red birds thusly: the brighter the red, the better the bird. (Why? See this post.) The better the bird, the better his genes/parental care/mate, and the better his reproductive success.

But sometimes it’s more complex—and interesting—than that.

Red male House Finch. Photo by M. LaBarbera.

Red male House Finch. Photo by M. LaBarbera.

Yellow and orange male House Finches. Photo by Ken-ichi Ueda.

Yellow and orange male House Finches.
Photo by Ken-ichi Ueda.

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What bird colors can tell you

Birds need to know a lot about each other. They need to know things like who will be the best parent; who will pass on the best genes; who could defeat them in a fight; and which offspring is worth investing in the most. One of the ways that birds can perceive such information about each other is by observing each other’s color signals—and the more researchers study these, the more it becomes clear that birds can tell a lot from color alone.

Let’s make up a bird species – the Superb Junco. This imaginary species has a black hood and pink bill like the Oregon Junco, but its body and tail are iridescent blue-violet. Here is an illustration of three individuals of this species:

superb_juncosThese individuals are clearly different: A has a paler head, B has a paler bill and is less brightly shiny, and C is brightly colored in all aspects. But what does that tell us?

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