14 February 2014

All for Love

Saved! A month ago I began a quest to find a special blog post topic for today, St. Valentine’s Day. Nothing could top the romance of my post of two years ago, my musical rose tribute to the Troggs’ Wild Thing (Happy Valentines Day!). Still, I pondered and searched and was finally rewarded!

Happy Valentine’s Day!
Welcome back. Two weeks ago, I greeted the Chinese lunar calendar’s Year of the Horse (Horse Year Caution). In my earlier post on discovering that I was a Horse (Astrology Time), I noted that the Horse would do anything for love, which sort of explains why I’m living on a farm in Wisconsin. But that’s nothing compared to what the túngara frog gives up for love.

Frog Love

The brown, rough skin túngara frog (Engystomops pustulosus; formerly Physalaemus pustulosus), shorter than 1.5 inches, dwells in lowland areas from northern South America to Mexico. Although I just learned about the frog, its breeding behavior is apparently well known to researchers. Early observational studies, for example, found that, during mating, the female produces a floating foam nest that becomes the baby tadpoles’ protective nursery.

Túngara frog with its air sac inflated.
(photo from commons.wikimedia.org)

While fascinating, this is a Valentine’s Day not Mother’s Day post. As such, I’ll highlight the recently published work by researchers representing the Smithsonian Tropical Research Institute in Panama, the Netherlands’ Leiden University, the University of Texas, Austin, and Maryland’s Salisbury University. Those investigators focused on the male túngara frog’s invitation to the female to, well, whip up some foam.

Ripple Alerts

Earlier studies captured the sounds of the male’s mating call and found that, along with attracting females, the calls were a magnet for predators in addition to alerting rival male frogs. The current study found that it’s not only the mating call that triggers the responses; it’s also the ripples in the water generated by the frog’s throat air sacs when it calls.

While rival male frogs generally responded to the competing suitor’s call by calling back rather mildly, they became agitated if there were water ripples in addition to the suitor’s call. Depending on the proximity, the rival either increased its rate of calling back, likely to challenge, or became silent, presumably to either avoid or prepare for a confrontation.

Equally if not more interesting is the finding that predatory bats use the ripples to echolocate the frog. Caged bats (Trachops cirrhosus) were exposed to two identical fake frogs, one with a mating call and the other with a call and water ripples. Ninety percent of the bats favored the frog near the rippled water, and there were 36 percent more attacks on that frog.

Wrap Up

It’s been observed that, in the wild, a frog that senses a bat overhead goes silent; yet once the mating call starts, ripples follow. The poor frog has a chance if he chose a pond covered with leaves and litter that might interfere with the bat’s echolocation, but the frog is driven by love not location. I can relate to that. How about you?

Happy Valentine's Day! Thanks for stopping by.


Research paper in Science:
Articles on the study on Science Daily and Livescience:
All about the frog on Wikipedia:

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