Small but Loud
3 The characteristics that make frogs so difficult to see,
however, also make it hard for them to find one another. That’s
why having a big voice is helpful. Frogs croak to tell other frogs
where they are. Their voices can be so loud that even a tiny frog
can be heard as much as a quarter of a mile away. But when frogs
feel the footsteps of a larger animal, they become silent. So
predators don’t know that the frogs are nearby.
4 Many of the world’s frogs live in rain forests. These regions are
filled with many different animals calling to their own species in
their own ways. These calls can sometimes make rain forests very
loud places. Frogs need to call loudly enough to be heard through
the noise in order to find other frogs.
Singing with Purpose
5 Peter Narins is a scientist who studies how frogs call to one
another. He makes recordings of frog calls and plays them back to
other frogs to see whether they will answer. He has learned that
frogs use their calls to help them tell friend from enemy. One way
they do this is to sing the same notes at the same volume each
time they call. When Narins plays back calls at a louder volume
than a real frog’s call, frogs do not call back.
6 In addition, Narins has found that frogs of the same species
always sing the same patterns. When Narins made recordings and
mixed up the patterns, the frogs didn’t call back. These patterns
are like a code that is distinct
from other animals’ calls and
difficult for others to copy.
7 Narins also observed that timing plays a role in frog calls.
Many frogs call only at a certain time of night. For example, the
coquí, a small frog that lives in Puerto Rico, calls only from sunset
to midnight. It waits for other frogs to finish their calls before it
begins making its “co-qui” sound.
GO ON