As It Happens

Ruff sex: Scientists identify genetic sequence of a bird with four genders

Biologists have discovered the group of genes responsible for ruffs, a type of sandpiper, having four different genders, including a male that looks like a female and tricks females into mating.
David Lank, a biologist at Simon Fraser University, holds a ruff. Plumage is everything in the bird world, and for a certain type of male ruff, scientists have found that genes are responsible for either the black-feathered aggressor, the white wingman or the cross-dressing mimic. Experts say those traits could hold clues to what's behind aggression in other species, and even humans. (Simon Fraser University/CP)

Talking about the "birds and the bees" is a tricky and delicate matter. Especially if you are referring to the mating behaviour of a particular bird called a ruff.

A ruff is a type of wading sandpiper. The female ruff looks similar to the type of sandpiper you may see at the beach. But the male ruffs are a more diverse bunch. There are three different kinds of male genders -- including a "female mimic." Scientists have known about this for a few years. But now a group of biologists has found the group of genes responsible for the unique gender diversity and behavioural traits in ruff sex.

"We try to avoid the use of that word actually because it takes you to strange places on an internet search engine," David Lank tells As It Happens host Carol Off.  "The enigma of the species is how there are three distinctly different kinds of males and how they co-exist in the same species."

Lank is a biology professor at Simon Fraser University and co-author of the new study.

The male genders are split into three categories: territorial males, satellite males or female mimics. Lank explains that during the mating season each gender competes for females in mating territories called "leks." 

Lank says the territorial males are identified by their dark plumage and aggressive behaviour within the groups. Whereas satellite males have white plumage and "instead of establishing their own territories they co-occupy the territories that have been created by the dark males."

By contrast, the female mimics lack any fancy plumage.

"They don't do fancy displays. They don't defend territories. They just hang out on the lek," Lank explains.

David Lank is a biology professor at Simon Fraser University. (Simon Fraser University)

But the behaviour of the female mimics is what makes them so unique. Lank explains that these masquerading males are opportunistic and try to blend in with female groups.

"They move around with the females and that helps them be in the right place at the right time," Lank explains.

Territorial males put on elaborate and aggressive displays to attract a female. The satellite males are less aggressive and actually compliment the territorial males.

"Invited as a co-display, kind of a wing man," Lank quips. "So although these males are competing they are also co-operating."

But the female mimic uses more underhanded methods.

"When a female crouches to mate they, quick as lightning, try to hop on her back and often one of the ornamented males will then be on his back and we'll have this little mimic sandwich," Lank explains.

The three types of male ruffs: female mimics, satellite males and territorial males. (Simon Fraser University/CP)

He adds: "[The] whole lek system is built around female choice of males. There are no forced matings or anything like that but it is hard to argue that she is mating with one of these males."

The mimics occasionally resort to even more devious tactics.

"[They] sometimes will crouch like a female and draw an ornamented male away from mating with a real female so they kind of decoy them away," Lank explains. "That's the most sophisticated thing that they do."

Lank says there are other species with three distinct male gender designations but stresses the importance of the gene sequence discovery.

"There is a small chunk of a chromosome with about 100 genes and that chunk holds all the genes that control a male's development into each of these three forms and how it subsequently behaves," Lank explains.

Lank has spent 30 years breeding ruffs trying to find out how this improbable gene sequence works and is transmitted. He says the study helps identify the dominant gene.

"It turned out that this little chunk of chromosome acts like a dominant gene," Lanks explains. "Half the kids of satellites are satellites, half the kids of mimics are mimics and if you don't have that form of the chromosome you are a territorial male."


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