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 ‘oklahoma’
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.
Usually during this time of year (December), we don’t think about amphibians or reptiles because most are spending the winter hidden to avoid freezing temperatures. However, Southern leopard frogs (Lithobates [Rana] sphenocephala) breed both in Spring and Fall in temporary ponds. As a result, ponds that retain water in late Fall and early Winter in eastern Oklahoma contain tadpoles of Southern leopard frogs. As the ponds shrink in size, the tadpoles become easy prey for herons and other water birds. In addition, as temperatures go down and the ponds shrink, the possibility exists that the ponds might dry up or freeze solid, killing the tadpoles. One such pond at our research site in Le Flore County is now filled with tadpoles and the water is dangerously low. Although it might seem that producing tadpoles when the possibility exists that the ponds might dry up or freeze is not in the best interest of the individual frogs that deposited the eggs, that is actually not the case. These frogs cannot predict whether ponds will last long enough or be refilled. However, one thing is for certain—if they do not breed at all, then there is no possibility that they will produce offspring in the event that ponds do last long enough in a particular year. Also, they can try again in Spring, and if they survive the Summer, yet again the following Fall. So, in effect, they are hedging their bets. Individual frogs that breed in Fall have some chance that they will produce offspring that will survive, whereas individual frogs that do not reproduce in Fall absolutely produce no offspring.
As fall arrives, Pygmy Rattlesnakes (Sistrurus miliarius) seem to crawl out of the woodwork, showing up on porches, in garages, under cars, and in flower beds throughout much of eastern Oklahoma, as far west as Norman and Oklahoma City. These beautifully patterned, small rattlesnakes have tiny rattles that are difficult to hear, and they often do not rattle when disturbed. Like other venomous pit-vipers (snakes in the family Viperidae that have heat-sensing pits below and between the nostril and eye), these small snakes can inflict a dangerous bite. The reason that we see these snakes during the fall is that they mate at this time of year, and, as a result, males are frequently seen as they search for females. They spend much of the rest of the year hidden, often under leaf litter. Our advice is to leave these snakes alone, and if they are close to your house, move them to a different location by carefully scooping them up on a rake or shovel. Remember, they have always lived here and hopefully always will, as they are part of our natural heritage. Teach your children what they look like so that they do not handle them.
Hello, interested readers. Herpetologists at the Sam Noble Oklahoma Museum of Natural History in Norman have been monitoring amphibians and reptiles in southeastern Le Flore County for the past year and have run across some interesting aspects of the biology of these often abundant and visible animals. We are so excited about our findings, and herpetology in general, that we decided to create this blog to keep others around the state, the nation, and the world informed.
As some of you already know, Dr. Laurie Vitt and Dr. Janalee Caldwell (us!) have spent many years studying amphibians and reptiles in the United States, Central America, South America, and a few other exotic places. We are professional researchers, but like most people who are fortunate enough to be paid for what they love to do, we started out by observing amphibians, reptiles, and other animals in their natural habitats when we were just children. So, in a sense, we never grew up! What we have learned directly from these animals is remarkable, and as you will see in the forthcoming blogs, the natural world is even stranger and more interesting than anything that we could make up.
We hope that you will join us by keeping up with our blog, and we will do our best to provide you with interesting information on these fascinating animals. For those of you who are particularly interested in amphibians and reptiles of Oklahoma, we invite you to visit our web personal pages, and more specifically, to examine the web pages that we have prepared for some of the Wildlife Management Areas (WMAs) around the state, in collaboration with the Oklahoma Department of Wildlife Conservation. We now have three WMA web pages, Packsaddle, Atoka, and Cookson, and all can be accessed from our WMA web page (http://www.snomnh.ou.edu/personnel/herpetology/vitt/WMA/index.shtml). We are working on more. We also have web pages for some of our South American research sites. So, for now, welcome to our blog, keep checking, and feast your imagination on this beautiful male Broad-Headed Skink from the Cookson Hills in NE Oklahoma.