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Tuesday, July 27, 2021

Column: Big love on the Great Plains

Life’s rough if you’re a male sage grouse.

First, you have to live in Montana, where there’s no In-N-Out Burger. Second, you will probably never get laid.

Spring is mating season for the sage grouse of the Great Plains. It’s a time for migration, vocalization and twitter-pation, but not a lot of action.

A male sage grouse is a bird about the size and shape of a turkey. It has a plump, grayish body with a frilly plumed tail. The males have two big “vocal sacks” that puff up like balloons and jiggle around as the male tries to woo the lady-grouse.

Alan Krakauer, postdoctoral researcher in animal behavior at UC Davis, told me about the elaborate sage grouse mating ritual.

What’s hot to a female grouse? Krakauer said the males start by rustling their feathers to make a noise like “when you walk in corduroy pants.” Then they flirt with a pattern of three low frequency “coo” sounds, one popping-sound and a whistle.

“The vocal sacks are used throughout most of the rapid movement and near the end during the pops and the whistles,” Krakauer said.

These randy males migrate every spring to traditional breeding grounds called “leks.” They will do the cooing/popping mating display hundreds of times a day. The female grouse (yes, grouse is the plural of grouse) get to pick their mates.

“The females basically get to shop around and check out the males,” Krakauer said. “It’s kind of like a singles bar.”

And – like in a singles bar – many males will strike out. These leks attract dozens to hundreds of males and females, but usually just one or two males get all the mating.

“It’s an unfair game,” Krakauer said. “A lot of males don’t ever get to mate.”

To the researchers, these male grouse all look the same. Same cooing pattern, same silly vocal sacks. Krakauer and his colleagues think the secret lies somewhere in the chorus of mating sounds.

When early naturalists first saw the grouse mating display, they noticed the males actually turned away from the females when they made the noises. The naturalists assumed the display was not meant to woo the ladies, but to impress other males.

“There are a lot of human analogies,” Krakauer said.

Researchers later discovered that by turning away from the females, the males were enhancing the pitch of the noises.

“We think [turning away] might help in the resonance of the sound, making the lower frequency sounds louder.” Kraukauer said.

For a talented few, the system works wonders. Dozens of female grouse will compete for the chosen male. Female grouse also practice mate-choice copying, which means they will choose a male without even seeing the mating display. If the female sees that a previous female has chosen a male, he is suddenly desirable.

After all the drama over mate-choice, I can’t help but be disappointed for the females. Birds, like doves and crows, have a pair-bond system where they stick together and help each other out with the babies. The male grouse, however, just move on to the next female.

“They probably don’t even know where the nests are,” Krakauer said.

This behavior is why the mating noises are so important. The tones somehow indicate the quality of the male’s genetics. The females aren’t looking for a male who will be a good provider; they’ve learned that males who sing a good song will produce superior chicks.

It seems like the selective breeding process would lead to population decline among grouse. Krakauer said that’s not how it works, though.

The breeding system is fine, but grouse numbers are declining due to habitat destruction. The region popular with grouse also holds deposits of methane and other natural gases. This fuel is valuable, so the grouse breeding grounds are disappearing. Without the leks, grouse don’t know where to meet up to mate.

As if those unlucky males need another thing to worry about.

MADELINE McCURRY-SCHMIDT thinks you should check out video of sage grouse mating displays on YouTube. Look up “greater sage grouse strut display” to see the birds filmed by UC Davis folks. E-mail her at memschmidt@ucdavis.edu.

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