Posts Tagged ‘frogs’

The First Spring Rains Bring Out Frogs and Salamanders

Wednesday, April 21st, 2010

Rains that occurred several weeks ago in southeastern Oklahoma brought out all of the early spring frogs, including Spring peepers (Pseudacris crucifer), Cajun chorus frogs (Pseudacris fouquettei), Pickerel frogs (Lithobates palustris), and Southern crawfish frogs (Lithobates areolata). Even Southern leopard frogs (Lithobates sphenocephala) and American toads (Anaxyrus americanus) were active. In addition to running our traps at our primary research site in Le Flore County, we spent time driving roads at night in both Le Flore and McCurtain Counties. Nearly every roadside pond contained some mix of the above frog species. The only two that did not occur together were Pickerel and Crawfish frogs.

An adult Cajon chorus frog

An adult Cajun chorus frog

A number of amphibian species in Oklahoma breed during late winter and early spring, and their nearly deafening choruses can be easily experienced by driving around in rural areas at night. Males congregate in ponds when rains first begin, and their calls attract females that have spent the fall and winter converting energy that they stored from spring, summer, and fall activity into eggs. Examination of ponds during the daytime usually reveals many egg masses attached to vegetation or floating on the pond surfaces.

In addition to frogs that reveal their presence by calling, salamanders are moving into ponds to breed. We found large numbers of Spotted salamanders (Ambystoma maculatum) moving across roads heading for ponds during rains, and we captured some in our traps. Unlike frogs, salamanders do not vocalize. Whereas female frogs are attracted to individual males by the quality of the call, female salamanders are attracted to individual males by the quality of their courtship behavior.

An adult Spotted salamander

An adult Spotted salamander

So, for those of you are interested in amphibians, drive around in rural areas when it begins to rain and listen for frog choruses.  With the windows cracked, you can hear choruses in breeding ponds along the roads.  If you find a chorus on public property, put on your boots, turn on your good flashlight or headlight (preferred), and see if you can locate individual frogs that are calling. Chorus frogs are tiny and usually call inside grass clumps at the surface of the water. A Chorus frog calling right at your feet can be difficult to locate and requires persistence. If you are lucky enough to hear the low snoring calls of Pickerel or Crawfish frogs, you will need to move slowly without sloshing the water.  Even slight movement of the water caused these wary frogs to stop calling and dive below the surface. If you stand quietly for ten minutes or so, males will reappear and begin calling.

Late Winter Frogs Will Begin Breeding Soon

Tuesday, January 26th, 2010

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!

cajun-chorus-frog-calling3

A male Cajun chorus frog calling

spring-peeper3

Adult Spring peeper

pickerel-frog_amplexus1

Male (top) and female (bottom) Pickerel frog in amplexus

Backtracking to Fall Breeding

Friday, December 18th, 2009

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.

Hoping for Rain—Southern Leopard Frogs

Friday, December 18th, 2009

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.

Adult Southern Leopard frog from southeastern Oklahoma

Adult Southern Leopard frog from southeastern Oklahoma

Amphibians and Reptiles at the SNOMNH

Thursday, September 3rd, 2009
Male Broad-headed Skink showing breeding coloration
Male Broad-headed Skink showing breeding coloration

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.