Brothers on a Hotel Bed

I’m a few days late on this one, but it’s never the wrong time to learn about the fascinating mating habits of turkeys. They don’t call them wild turkeys for nothin’.

You know that saying “It takes two to tango”? Well, in their case it takes three, four, or five.

File:Male north american turkey supersaturated.jpg

Male north american turkey (Meleagris gallopavo) – Wiki Commons

No, no, no – not in that sense.

Mating systems where males form large groups to attract females are called leks, which means ‘play’ in Swedish . Many bird species form leks, in which the males competitively display their stuff to get female attention. Meanwhile, the female wanders from male to male to judge them before making her final pick.

The thing about leks is that they are competitive. Males of most organisms engage in competition of some kind to win the girl. Which is why something like this rhinoceros beetle is equipped with such fabulous weaponry.

But in turkeys, within the larger, competitive leks, are smaller coalitions of two to four males that cooperate with one another. These unique display partnerships in which males cooperatively court females are found in only a few species of birds.

What’s even weirder is that only one of the males (the dominant) actually gets to mate with the female that the group attracts. The other male or males, the subordinates, get no reproduction at all. Nothing. Zilch. Nada. This is akin to Batman getting all the ladies and Robin helping for no other reason than to help Batman get all the ladies. Rather strange, isn’t it?

So why would these subordinate males engage in such altruism, benefiting another at a cost to itself?

Further investigation by Alan Krakauer (then a PhD student) revealed that these duos or groups are formed by close relatives, often brothers. So while it seems that the subordinates are getting nothing for their efforts, they are actually indirectly benefiting by helping out a close relative.

Both of them gain by cooperating. The dominant does better with the subordinate’s help. Likewise, the subordinate does better as a back-up strutter rather than trying to strut his stuff all by himself. Most important of all is that the benefits for helping outweigh the costs.

This famous saying by J.B.S. Haldane gets at the heart of the matter: “Would I lay down my life to save my brother? No, but I would to save two brothers or eight cousins.”

In other words, you share roughly 50% of your genes with your siblings, so saving two of them is equal to saving yourself, who you are 100% related to. Similarly, you share roughly 12.5% of your genes with your cousins, so eight of them equals 100% of you. All this to say, the number of genes you share with your relatives matters.

And in the case of the turkeys, subordinate males gain no direct benefit (i.e. having offspring of their own) by helping, but they do gain indirect benefits by helping their close relatives have offspring. This is called kin selection, and it provides us with an explanation for such altruistic acts as cooperative male display in turkeys.

Now, if we could just figure out what’s in it for Robin.

You can read the original work on turkey courtship displays here and a popular press story about it here.

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