Biology of Pond Frogs

see also Lake Macquarie

Frogs are amphibians most of which have a distinctly two staged lifecycle the first aquatic and the second terrestrial. Survival of frog populations requires suitable spawning, tadpole, juvenile, and adult habitats.

Frog egg masses are laid in water and develop into a browsing filter-feeding tadpole that eventually metamorphoses into a juvenile frog. The number of eggs varies from 20 to 50,000, the number depending mainly on the size familyFor instance toads typically lay many thousands of small eggs. Eggs may be laid in foam nests, gelatinous egg strings, separately, or in shallow depressions next to ponds. In some pond frogs, such as Striped Marsh Frogs (Lymnodynastes peronii), males guard the eggs. Tadpoles filter pond water for algae, bacteria and sediment and increase water clarity and quality. They also provide an efficient conversion of pond nutrients and energy to food for wading birds and aquatic reptiles.

Frogs may be explosive breeders in which most of the population spawns over a short period after heavy flooding rain following a dry period. Summer explosive breeders generally have a shorter period from egg to juvenile than winter breeders. Alternatively they may breed continuously over a long season sometimes with the same female laying eggs on several occasions.

Juvenile frogs leave the aquatic environment and feed on invertebrates such as insects. Leaving the aquatic environment may consist of simply occupying emergent vegetation or pool side shelter, or may involve considerable migration. During this period the juvenile frog is particularly vulnerable to predation, undergoing a dramatic body reorganisation and being restricted to pond margins. Juveniles rapidly grow to maturity with most breeding in the first year. During suitable weather male frogs return to breeding sites and begin calling to attract females. Only male frogs call. They may congregate to form choruses in the short term or may call over time from established territories. Calling frogs do not necessarily mean successful spawning.

When not spawning many frogs are difficult to find and their importance as predators and prey may be underestimated. Adult survival and abundance, assuming good breeding conditions, is dependent on the amount of suitable habitat. Surprisingly some frogs sun bake to increase their body temperature allowing them to digest food and grow faster. They wipe secretions over themselves to provide a sunscreen that reduces water loss. Recently, for unknown reasons, many frogs have declined or become extinct.