Anurans are four-limbed, terrestrial
juveniles and adults completely lack true tails. Based on the morphology,
they are categorized into frogs and toad. Generally, frogs are smooth
skinned, aquatic amphibians, whereas toads have rough and warty skin,
bony ridges and prefer terrestrial conditions. Anurans hindlimbs and feet
are greatly elongated. Body is more adapted to light weight and strength
are the most important communication signals for anurans. Only males of
the anurans produce calls. This is used as advertisement calls (to attract
the female during breeding season and to advertise the ownership of territory),
aggressive calls (to defend from other males). There are other types of
calls, namely reciprocal calls (soft low calls from females [either during
courtship (also referred as advertisement calls) or reproductive stage].
Females do not have a vocal sac and very few can vocalize. Females sometimes
give very low reciprocal call for the male advertisement calls. When producing
the calls, male force the air into their lungs with positive pressure
excreted by throat muscles. When these muscles contract, air is forced
out of the lungs and into the buccal cavity.
Of the three
orders, anurans are most wide spread. Frogs are found in all continents
except in Antarctica.