Choosing The Closest Guy Sometimes Makes Sense — For A Frog

strawberryfrogThe strawberry poison frog (Oophaga pumilio) is instantly recognizable, with its bright red coloring that announces to potential predators “don’t eat me.” These tiny amphibians — which reach only a couple centimeters in length — are common in their range, stretching from Nicaragua through Costa Rica and into Panama.

In 2004 and 2005, a group of researchers, led by Ivonne Meuche of the Institute of Zoology in Hannover, Germany, tracked strawberry poison frogs in Hitoy Cerere Biological Reserve in Costa Rica during their mating seasons. The scientists wanted to figure out how females chose their male mates, and the results of their study were just published in Frontiers in Zoology. The surprise — females usually just pick the first guy they encounter.

In this species of frogs, females are free to mate with the male of their choice. A female will move into her chosen male’s territory and engage in a little nooky, laying her eggs in the leaf litter. Ten days later, the female will move her newly hatched tadpoles into small pools of water in the leaves of bromeliads or bananas — one tadpole per leaf — and feed them.

When it’s time for the frogs to pair up and make more little frogs, the males call to females. A female could potentially use those calls to judge the males, choosing the best out of the lot. But that’s not what they do, the researchers found. Instead, females mostly just pick the guy that’s closest.

This would probably not be a good strategy if you were a human. Just think about the creeps you meet when out at a bar. Proximity is often not a plus in such a situation. But life is different if you’re a strawberry poison frog. Potential guys are not conveniently grouped together. If a girl frog wants to take a look at multiple males and judge their worthiness, she runs the risk of expending too much energy, which could have gone into producing better, possibly more successful eggs. (Only about a fifth of the eggs laid during the study hatched. Most dried out or were lost to predators.) And if she’s too choosy and doesn’t find a mate, then she might not be able to have any of her eggs fertilized.

Not mating at all is a big risk because there are usually more females than males, at least in the population studied. Under such a situation, it might be better to just pick the first guy you meet. (I imagine there are some universities where the female-male ratio is similar to strawberry poison frogs and thus even the creepy guys get girlfriends.) But while that might mean that some loser males get to pass on their genes, every non-picky female will get to pass on hers. And when you’re a strawberry poison frog, that’s what matters in life.

Image credit: Ivonne Meuche, Oscar Brusa, Karl E. Linsenmair, Alexander Keller and Heike Pröhl, via EurekAlert