Just after our last blog, rains brought frogs and salamanders out all over the place, which sent us racing around different parts of southeastern Oklahoma. We also ran our drift fence traps at our field site in Le Flore County, trying to keep up with movements of amphibians. A brief trip to Florida to present a talk to one of the Florida herpetological societies in Gainesville interrupted our amphibian and reptile excursions in Oklahoma, but only for about a week. As a result, we have been so busy that we have not been able to keep up with our blog. However, as the title says, we are back, and we will try to catch you up on what we have been doing in the following series of blogs. We hope you will all stick with us, and many thanks for all of your kind comments.
Posts Tagged ‘breeding’
We are eagerly awaiting the first calls of the late winter-breeding Cajun chorus frogs (Pseudacris fouquettei), Spring peepers (Pseudacris crucifer), and Pickerel frogs (Lithobates [Rana] palustris). These frogs begin migrating to ponds, roadside ditches, and marshy areas with the first sign of warming weather and substantial rainfall. Spring peepers and Pickerel frogs occur only in the eastern third of Oklahoma, whereas various species of Chorus frogs occur throughout most of Oklahoma.
The Chorus frogs and Spring peepers are small frogs in the treefrog family (Hylidae). Chorus frogs are brown with darker brown stripes. Spring peepers are yellowish, with an irregular X on the back, from which the name, crucifer, is derived. Calls of these two frogs are easily distinguished. The Chorus frog call is a slow trill, similar to running a finger over a comb. In contrast, the call of the Spring peeper is a single loud whistle. When numerous individuals of these two species call from the same pond, the sound can be deafening! Males of both species call from perches on shrubs or small trees at the edge of the water or from clumps of vegetation in the water.
Pickerel frogs, which are in the “true” frog family (Ranidae), are moderately large frogs with two rows of squarish spots on the dorsum. Each frog has a different spotting pattern, making it easy to tell individuals apart. Pickerel frogs typically begin breeding in middle to late February, continuing into March. Their call is a low snore and can be difficult to hear if they are breeding in the same ponds as the louder Chorus frogs and Spring peepers. In addition, Pickerel frogs sometimes call under water, muffling their sound even more.
More to come when the frogs start 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.