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The Smithsonian Tropical Research Institution (STRI) in Panama, is a bureau of the Smithsonian Institution based outside of the United States, is dedicated to understanding biological diversity.
Male Túngara frogs call from puddles to
attract females. The production of the call
incidentally creates ripples that spread across
the water. Researchers at the Smithsonian
Tropical Research Institute in Panama revealed
that these ripples are used by other male
frogs to assess the level of competition in the
puddle. Unfortunately for the frogs, their main
predator, the frog-eating bat, senses the ripples
too, making the frogs easier targets.
The tún-gara sound of a tiny rainforest frog
known to scientists as Physalemus pustulosus
has been compared to a peacock’s train.
Female frogs are attracted in large numbers
to the ponds from which the males call night
after night. But these calls also make it easier
for frog-eating bats, Trachops cirrhosus, to find
their prey. New work by a team from STRI, the
University of Leiden, the University of Texas at
Austin and Salisbury University in Maryland
shows that much more is going on.
“It’s comparable to the use of lip reading,” said
STRI post-doctoral fellow Wouter Halfwerk
from the University of Leiden. “While sound
is the most obvious component of the frogs’
communication, the call-induced ripples
alter the behavior of competing males that
sense them. Bats perceive the ripples too,
using echolocation, which shows that the
costs associated with communication can be
imposed through a sensory domain that is
fundamentally different than the intended
receiver of the frog’s call.”
Competing male frogs increased their call rate
by more than double when presented with
ripples and sound as opposed to sound alone.
Males stopped calling when they were inside
the 7.5-centimeter defended zone of ripple-
generating rivals, suggesting that ripples are
used for competitive interactions. Males did
not respond to ripples alone, showing that the
cues derived from them have to be integrated
with the accompanying sound to elicit the