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Frog Calls
Frog Calls
October, 2014
Newsletter of Crosstimbers Connection Volume 2, No.3 f October, 2014
Field Trips & Presentations – Summer & Fall Events in July Through October During the hottest part of the summer, we planned indoor presentations at the Fort Worth Nature Center & Refuge (FWNCR). We avoided the heat and drought, and everyone who came seemed to have a good time. On July 5th, Michael gave a talk about venomous snakes of our area, complete with slides and a copperhead and pygmy rattlesnake for people to see. Then, in August the presentation covered the nonvenomous snakes of our area, and our big, friendly bullsnake was a big hit with everyone. Then, in September we covered frogs and toads, bringing lots of slides and audio clips of the distinctive calls of each species. Also in September, we once again visited the Clear Fork of the Trinity River in Benbrook, with Nic Martinez as our interpreter of all the things in and around the water. We netted several species of fish, including green and long-ear sunfish. We also found many crayfish, either trapped in pools or seeking shelter in the river’s muddy bottom. The drought is taking a toll on the river’s flow, but we made the best of the pools of water that were still there. One of the crayfish appears to have been a red crayfish or “red swamp crayfish,” Procambarus clarkii, a species that the book Texas Crawdads reports has Page 1
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Field Trips & Presentations been seen in Dallas but not Tarrant County (where we were). Dominic found a tiny juvenile Texas brown snake, and of course we saw cricket frogs on most of the muddy banks. Just as we had last year, we seined up ghost shrimp and harmless water
Above: red crayfish; left: sunfish; below: water primrose
scorpions. Nic was a never-ending source of information about all these animals. He also filled us in on some of the vegetation along the banks, including the invasive water primrose and the little widow’s tear that traps a “teardrop” of water in the flower. As fall arrived, we had a booth at FWNCR’s “Monster Bash,” a celebration of the legendary goat-monster that some claimed to have seen back in 1969 around Greer Island. The fall weather was perfect, and we talked with many visitors who loved the bullsnake and our box turtles. A week later, our talks branched out from herps to invertebrates, with Clint King talking with people about butterflies, moths, beetles, and other insects. He described ways of looking for and capturing these critters with nets and, for some, using lights to attract them at night. He also set up a light outside the Hardwicke Interpretive Center to see what might be drawn to the light. We took participants on a short walk after the talk, looking for invertebrates in the gathering darkness. We saw a rare black witch moth right at the door to the center, and then found other things in the surrounding area, including a wheel bug and a centipede.
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Field Trips & Presentations Below: Clint and others, checking for insects attracted to the light; right: the black witch moth
These events have been a great deal of fun for us to provide, and we believe those who have attended have had a great time. We look forward to continuing our field trips and presentations – Michael will present about turtles in November, and Clint will talk about arachnids (spiders and their kin) in December.
Don’t Miss Out! Our next programs at Fort Worth Nature Center & Refuge November 1, 2 to 3pm: Tu rt le s of N ort h T ex as - Several species of turtles are common in north Texas, and they get some protection from their bony shells. Come find out whether that shell still gives them the protection that they need in the modern world. We’ll look at a couple of native turtles close up, and then if weather permits we’ll take a walk to look for some turtles and other reptiles and amphibians. December 6, 2-3pm: Arac h noph il ia - This program is about spiders and their kin (“arachnids”) and their interesting forms and life histories. Some spiders build webs with amazing geometric patterns. Scorpions glow blue-green when we shine a black light on them. And out in west Texas, the bizarre vinegaroon looks a little like a scorpion but instead of stinging it squirts a stream of vinegar toward anything that threatens them. Come see slides and hear stories of these amazing animals. (While Crosstimbers Connection does not charge a fee, there is an entrance fee to the nature center-see their website, www.fwnaturecenter.org)
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Frog Calls
October, 2014
Our Long-Lived Turtles Dinosaurs Got Nothing on These Amazing Survivors By Michael Smith Some time around 225 million years ago, give or take a few years, some very early reptiles developed armor plates across their backs that made their day-to-day survival a little easier. Back then, at the dawn of the age of dinosaurs, turtles got their start. They have been around ever since, watching the Brontosaurs and Tyrannosaurs come and go, seeing sabre-toothed tigers and mastodons have their day, and keeping on going in that steady and deliberate way that turtles have. Turtles are one of nature’s most amazing success stories. Their shells are made of modified ribs and other skeletal parts. Imagine a backbone, ribcage, and breastbone expanded and re-tooled to cover most of your body, and covered with a thin layer of living tissue that grows material like fingernail. Imagine that your neck bones were so flexible that you could bend them in a tight S-curve that would pull your head back inside this modified ribcage. You’re beginning to get the idea of what it would be like to be a turtle. Back in prehistory, starting in the Triassic period of the Mesozoic era, the earliest turtles arrived on the scene. One of them, Proganochelys, would have been over three feet long and had a shell with a top (the carapace) and a bottom (the plastron) similar to modern turtles. Proganochelys would not have been able to pull its head inside its shell, however. Turtles then branched out to different sizes and different habitats. For example, Archelon was a turtle that lived in the shallow seas in parts of North America late in the age of dinosaurs. This sea turtle’s skeleton measures about 13 feet in length, making it the largest turtle that ever lived, as far as we know. It would have shared some similarity with the modern leatherback sea turtle, with a shell that was a bony framework covered with tough, leathery flesh. It is also thought that Archelon lived for a very long time, which is another trait that turtles are famous for. Some modern species of turtles live very long lives. The box turtles that we still sometimes see in north Texas may live nearly as long as humans at times. While the ornate box turtle may generally live for between 20 and 30 years (and
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Our Long-Lived Turtles sometimes longer), the three-toed box turtle may live longer than that. The threetoed box turtle is a subspecies of the eastern box turtle, and in some places the eastern box turtle often lives more than 50 years. A few of those turtles even live to 100 or more years. The red-eared slider that we often see in ponds and rivers can live for over 30 years. The yellow mud turtle, found in smaller ponds and cattle tanks in our area, may have a similar life span. With old age comes wisdom, at least
Three-toed box turtle
sometimes, and perhaps that is the reason
that people have made up many stories of turtles as being old and very wise (as in the book, Old Turtle, by Douglas Wood). The long lives and strength of turtles may also help explain why many creation myths feature turtles holding up the world. In a couple of versions of Hindu mythology, a tortoise is like a foundation, for example, supporting an elephant on which the world sits. Similar myths are found in China and Mongolia. Here in North America, a Sioux myth was that the world was actually the shell of a giant turtle floating on the waters. Positive qualities have been assigned to turtles in stories and literature, such as in Aesop’s fable of the Tortoise and the Hare. In it, the turtle’s steadfast plodding determination wins against the arrogance of the faster rabbit. In stories, turtles are slow plodders, but in real life they are sometimes faster than we might imagine. This is especially true of semiaquatic turtles swimming in streams and ponds. With strong limbs and feet that are somewhat webbed, the map turtles and sliders and similar turtles can put on a burst of speed. And those who have seen sea turtles swim usually think of birds flying through the air. With their forelimbs modified as flippers, these chelonians fly through the waters with grace and agility.
Mississippi mud turtle: left – the carapace or top shell; right – the plastron or bottom shell
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Our Long-Lived Turtles
Our semiaquatic turtles are often seen basking on logs and branches sticking out of the water – why would they do that? Basking in the sun has several uses for turtles. First, drying off may discourage growth of parasites or fungus that may be picked up in the water. Second, basking exposes the turtle to the ultraviolet spectrum of sunlight, and UV-B is necessary as part of most turtles’ metabolic activity for bone health. The primary function of basking seems to be the regulation of the turtle’s temperature. A turtle that has pulled out of the water onto a log, with the shell facing the sun, can raise its temperature so that it is much warmer than the water. Remember that turtles are “cold-blooded,” meaning that they do not generate body heat like we do. Their bodies function best within a moderate range of temperatures, and their metabolism generally increases as they get warm. And so, they need to use their environment in order to warm up, and basking in the sun is a great way to do that. North Texas is home to numerous turtle species. We have box turtles, the red-eared turtle, the Texas cooter and river cooter, several mud and musk turtles, softshell turtles, the chicken turtle, and the common snapping turtle (and occasionally we see the alligator snapping turtle in the eastern counties). Several of these are fairly common, while others are not often seen and some seem to be declining in numbers. In fact, around the world turtles are experiencing what many biologists are calling an extinction crisis. Of the approximately 300 species of turtles, about one-third are at risk of becoming extinct in the next 20 years. Much of this is due to the overuse of these animals for food and for traditional practices in Asia and other places. Even in the United States, some populations of turtles have been wiped out because of people catching them and taking them home as pets. Additionally, fields, marshes, and ponds often disappear because we develop them and build things where turtles used to live. Many turtles are run over on the roads. These animals outlived the dinosaurs, but many of them may disappear because of human activity. There are things we can do to help turtles, such as protecting some wild places where turtles live, trying not to hit them while we are driving on the roads, and leaving them where they are when we see one in the wild. More information about how to help turtles is provided by the Turtle Survival Alliance (http://www.turtlesurvival.org). You can find more information about the turtles of Texas at the Texas Turtles website (http://www.texasturtles.org).
Fort Worth Nature Center & Refuge
Crosstimbers Connection - connecting people with nature in north Texas We take people out into the woods and prairies, looking for reptiles, amphibians, and other wildlife, learning and having fun. And we do it without charging anything (but we gladly accept contributions to keep us going). We are a nonprofit organization - please visit us on the web at: http://crosstimbersconnection.org. Michael Smith, President
Rob Denkhaus, Board Member
Debbie Dorman, Secretary
Nic Martinez, Board Member
Jo Smith, Treasurer
P.O. Box 151882 h Arlington, Texas 76015 Page 6