Purpose
The primary purpose of the vocal sac is to amplify the advertisement call of the male, and attract females from as large an area as possible. Species of frog without vocal sacs may only be heard within a radius of a few metres, whereas some species with vocal sacs can be heard over 1 km (0.62 mi) away. Modern frog species (Neobatrachians and some Mesobatrachians) which lack vocal sacs tend to inhabit areas close to flowing water. The sound of the flowing water overpowers the advertisement call, so they must advertise by other means.
An alternative use of the vocal sac, is that employed by the frogs of the Rhinodermatidae family. The males of the two species of this family will scoop recently hatched tadpoles into their mouth, where they will move into the vocal sac. The tadpoles of Darwin's Frog (Rhinoderma darwinii) will remain in the vocal sac until metamorphisis, whereas the Chile Darwin's Frog (Rhinoderma rufum) will transport the tadpoles to a water source.
Read more about this topic: Vocal Sac
Famous quotes containing the word purpose:
“Your good mother tells me you are feeling very badly in your new situation. Allow me to assure you it is a perfect certainty that you will, very soon, feel betterquite happyif you only stick to the resolution you have taken to procure a military education. I am older than you, have felt badly myself, and know, what I tell you is true. Adhere to your purpose and you will soon feel as well as you ever did.”
—Abraham Lincoln (18091865)
“The purpose of a work of fiction is to appeal to the lingering after-effects in the readers mind as differing from, say, the purpose of oratory or philosophy which respectively leave people in a fighting or thoughtful mood.”
—F. Scott Fitzgerald (18961940)
“The very purpose of existence is to reconcile the glowing opinion we have of ourselves with the appalling things that other people think about us.”
—Quentin Crisp (b. 1908)