and why do frogs croak?
croaking that we hear is done by male frogs. Males call mainly for
2 reasons: either to attract females that are ready to mate or to
repel other males from a territory.
When calling, a frog forces air from its lungs
through the larynx, causing the vocal cords to vibrate and produce
the sound. The sound is then amplified by the vocal sacs.
Vocal sacs are pouches of skin beneath the floor
of the mouth When calling, a frog keeps nostrils and mouth closed
and uses muscles of the body wall and throat to shunt air back and
forth between the mouth-sac cavity and the lungs.
D200 with Sigma 70-300mm APO DG Macro 1/125sec at f10 ISO 320, Flash
Enchyclopedia of Reptiles & Amphibians - Dr. Harold G. Cogger
& Dr Richard G. Zweifel