Carl Zimmer in the New York Times:
A croak is how male green frogs tell other frogs how big they are. The bigger the male, the deeper the croak. The sound of a big male is enough to scare off other males from challenging him for his territory.
While most croaks are honest, some are not. Some small males lower their voices to make themselves sound bigger. Their big-bodied croaks intimidate frogs that would beat them in a fair fight.
Green frogs are only one deceptive species among many. Dishonesty has been documented in creatures ranging from birds to crustaceans to primates, including, of course, Homo sapiens. “When you think of human communication, it’s rife with deception,” said Stephen Nowicki, a biologist at Duke University and the co-author of the 2005 book “The Evolution of Animal Communication.” “You just need to read a Shakespeare play or two to see that.”
As Dr. Nowicki chronicled in his book, biologists have long puzzled over deception. Dishonesty should undermine trust between animals. Why, for example, do green frogs keep believing that a big croak means a big male? New research is offering some answers: Natural selection can favor a mix of truth and lies, particularly when an animal has a big audience. From one listener to the next, honesty may not be the best policy.