Sunday, October 7, 2012



Life Cycle of a Frog

True Love?
[toads mating] When Frogs mate, the male frog tends to clasp the female underneath in an embrace called amplexus. He literally climbs on her back, reaches his arms around her "waist", either just in front of the hind legs, just behind the front legs, or even around the head. Amplexus can last several days! Usually, it occurs in the water, though some species, like the bufos on the right mate on land or even in trees!
(photo courtesy of Emile Vandecasteele)
While in some cases, complicated courting behavior occurs before mating, many species of frogs are known for attempting to mate with anything that moves which isn't small enough to eat!

Spawn (egg-mass)
[frog spawn] [toad spawn] While in the amplexus position, the male frog fertilizes the eggs as they get are laid. Frogs tend to lay eggs single eggs in masses, whereas toads usually lay eggs in long chains.
Some frogs leave after this point, but others stick around to watch over the little ones. Some have very unusual ways of caring for their young. You'll learn about some of those later in this tour!.

Frogs and Toads tend to lay many many eggs because there are many hazards between fertalization and full grown frogness! Those eggs that die tend to turn white or opaque. The lucky ones that actually manage to hatch still start out on a journey of many perils.
Life starts right as the central yolk splits in two. It then divides into four, then eight, etc.- until it looks a bit like a rasberry inside a jello cup. Soon, the embryo starts to look more and more like a tadpole, getting longer and moving about in it's egg.
Usually, about 6-21 days (average!) after being fertilized, the egg will hatch. Most eggs are found in calm or static waters, to prevent getting too rumbled about in infancy!
Some frogs, like the Coast foam-nest treefrog, actually mate in treebranches overlooking static bonds and streams. Their egg masses form large cocoon-like foamy masses. The foam sometimes cakes dry in the sun, protecting the inside moisture. When the rain comes along, after developement of 7 to 9 days, the foam drips down, dropping tiny tadpoles into the river or pond below.

[tadpole] Shortly after hatching, the tadpole still feeds on the remaining yolk, which is actually in its gut! The tadpole at this point consists of poorly developed gills, a mouth, and a tail. It's really fragile at this point. They usually will stick themselves to floating weeds or grasses in the water using little sticky organs between its' mouth and belly area. Then, 7 to 10 days after the tadpole has hatched, it will begin to swim around and feed on algae.
After about 4 weeks, the gills start getting grown over by skin, until they eventually disappear. The tadpoles get teeny tiny teeth which help them grate food turning it into soupy oxygenated particles. They have long coiled guts that help them digest as much nutrients from their meadger diets as possible.
By the fourth week, tadpoles can actually be fairly social creatures. Some even interact and school like fish!

Tadpole with legs
[tadpole] After about 6 to 9 weeks, little tiny legs start to sprout. The head becomes more distinct and the body elongates. By now the diet may grow to include larger items like dead insects and even plants.
The arms will begin to bulge where they will eventually pop out, elbow first.
After about 9 weeks, the tadpole looks more like a teeny frog with a really long tail. It is now well on it's way to being almost fullgrown!

Young Frog, or Froglet
[froglet] By 12 weeks, the tadpole has only a teeny tail stub and looks like a miniature version of the adult frog. Soon, it will leave the water, only to return again to laymore eggs and start the process all over again!

By between 12 to 16 weeks, depending on water and food supply, the frog has completed the full growth cycle. Some frogs that live in higher altitudes or in colder places might take a whole winter to go through the tadpole stage...others may have unique development stages that vary from your "traditional" tadpole-in-the-water type life cycle: some of these are described later in this tour.
Now these frogs will start the whole process again...finding mates and creating new froggies.


Frog life cycle