Backtracking to Fall Breeding

During Fall, when temporary ponds fill with water in southeastern Oklahoma, thousands of Southern leopard frogs come in to breed. Males enter the ponds at night, usually when it is raining or within several nights following the rain. Males call to attract females, and, after a female selects the male with which she will mate, the frogs amplex. Although amplexus varies among frog species, Southern leopard frogs amplex with the male on top of the female with his front legs wrapped on the body of the female just behind her front legs. This is called inguinal amplexus because of the position of the male’s front legs. As you probably know, fertilization is external in almost all frogs, so the male releases sperm over the eggs as the eggs are being laid, fertilizing the eggs. The eggs are laid in a mass attached to vegetation in the water. If the pond doesn’t dry up, the eggs hatch into tiny tadpoles. Temporary ponds are usually rich in nutrients in Fall, and as a result, most surfaces in the ponds are covered with algae, and huge populations of various insects and other invertebrates build up as time goes on. The tadpoles feed on algae, scraping it off of the surfaces with tiny teeth surrounding the mouth. Because tadpoles of Southern leopard frogs are vegetarians (herbivores), nearly all of their digestive system is intestine.  If you closely examine a tadpole, you can see the intestine through the skin. Once tadpoles hatch from eggs, the real race begins. Individual tadpoles face an uncertain future. The pond can dry up before they transform into a terrestrial frog. Also, aquatic birds and many insects, including larvae of dragonflies, damselflies, and predaceous diving beetles, eat tadpoles. Tadpoles eat and grow as fast as they can so that they can get out of the pond before it dries and so that they can get bigger than some of their predators (aquatic insects). One of the particularly fascinating things about frogs is the remarkable change in lifestyle that goes with transformation from a tadpole to a young frog. This will be a topic for a future blog, so keep posted.

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