Friday, June 10, 2011

Some Thoughts on Frog Sex and Predation

Around this time of year the farmers start planting their rice seedlings which have been growing in neat trays inside greenhouses. In order to do that they flood the fields in just about perfect timing with the advent of the rainy season.

Now, I'm not sure where the frogs have been hiding all this time, but they are suddenly quite vocal about the surge in water. In the early evening they start up a croaking chorus which becomes a perfect sleeping accompaniment later at night.

Early this evening I was riding my bicycle back from work when, as I passed our neighbor's rectangular rice paddy, I heard the half-hearted peeping of one lone frog. No one dared to join him at that moment and so, after one or two more trailing peeps, he went quiet.

This frog's awkwardness made me think about the sexual imperative of peeping versus the steep cost of potential predation. Peep first and loudest and you might have a better chance of securing the right mate and thus passing on your genes — but peep too soon absent other peepers to help cover you, and you have a greater chance of being snatched by that skulking snake or bird.

I'm guessing that's one of the reasons that frogs chorus. It's a lot safer to be singing together than alone. If a predator touches down anywhere in the chain, the whole lot goes silent. But how does everyone know?

All right. So I got this far in my thinking and realized there was more that I didn't know than I did. So I started poking around the internet, looking at studies. Now I realize that not all frogs species are the same, but I'm guessing that the possession of frogness, like the possession of personhood (we all walk on two legs, all speak, all have opposable thumbs, etc) means that certain shared characteristics result in certain shared behaviors across frog species.

Research being carried out at Brown University by Andrea and James Simmons (you can read about it here) suggests that their species of bullfrog clusters in groups of four to six when it's time to chorus. The Simmons's hypothesis is that the frogs gang up in this way to form a kind of superfrog which can more easily attract multiple females.

"Sometimes they're polite animals who take their turns," says Andrea Simmons. "But as the season progresses, they become more and more prone to calling at the same time. This would make it hard for a female bullfrog to distinguish one male from another."

But I'm guessing that they have only half of the equation correct. To gang up in this way also confers protection. Eyes and ears in every direction.

In my mind there's a reason that as the season progresses there are fewer and fewer lone croakers — they've perished from their foolishness of singing alone.

To call out alone is to die alone. To call out together is another matter entirely.

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