Frog CallsNewsletter of Crosstimbers Connection

Volume 1, No. 3 v July, 2013

The Search forSummer Frogs

With Nolan High School Students atFort Worth Nature Center & Refuge

On June 22, Crosstimbers Connection teamed up with the FortWorth Nature Center & Refuge to provide some students a wet-land outing in search of frogs and toads. Five biology studentsfrom Nolan Catholic High School, along with teacher Bill Richer-son, came to learn about local anurans (frogs and toads) andtheir calls. We showed pictures of lots of these amphibians andlistened to recordings of their calls.

Afterwards, we visited several places on the refuge, starting withthe marsh boardwalk. In the gravelly area near the parking lotwe spotted a six-lined racerunner, an alert and fast lizard withstripes down its back and a beautiful wash of yellow-green on itsshoulders and head. On the boardwalk we saw and heard in-sects, birds, and fish, and though we looked for green treefrogs,we did not see any.

Then we moved on to the bottomland woods at the north end ofthe marsh. Hopping across the trail was a very small toadlet,which was a toad that had just metamorphosed from a tadpoleand was still small enough to sit on your fingernail, if we couldjust get it to sit still. We also found a couple of little brown skinksslithering around in the leaf litter with their tiny legs and longbodies. Exploring around a dry place where running water hadpreviously made clumps of branches and leaves, we found awhite-footed mouse. This mouse, with white fur along its under-parts and big dark eyes, paused for a photograph before scam-pering off. There were a number of invertebrates to find,including a beautiful underwing moth on a big tree trunk. Atone point, Debbie spotted a three-toed box turtle wanderingthrough the woods in the late afternoon shadows.

Heidi examines a toadlet

Frog Calls July, 2013

Page 2

We took a walk on Greer Island at the end, as the lightof day was failing and it was time to use our flashlightsto find our way. We started hearing the “wank-wank-wank” of green treefrogs, and by the time it was fullydark, on the causeway off the island, the reeds to ourleft were loud with the choruses of these beautifulgreen frogs.

The students had been great, and we thanked eachother for a good time before they boarded the bus forhome. One girl said she appreciated our showing herthis place, saying that she really had not had this kindof experience before. And this made our day – Mark,Debbie, and Michael went home very happy to havehad a hand in sharing this place with these great kids.

The Search for Summer Frogs (continued)

White-footed mouse

Underwing moth

Speaking of Green Treefrogs…

We went on two "herp walks" on May 25th at Ft. Worth Nature Center& Refuge - each with a family with a couple of young children. We hadfun checking out the boardwalk, talking about green treefrogs andthen seeing them (and in one case getting to watch him call with hisdistended throat pouch). We showed one family a small leopard frogthat they were thrilled with. They were equally thrilled with the fivelined skink we got a glimpse of, the red-winged blackbird in the marsh,the various snails, and the kids loved the "roly-polys." Young kids havea wonderful ability to see amazing things in some of the smallest crea-tures!

Green treefrog

Frog Calls July, 2013

Page 3

A Water Snake Copes with Summer HeatBy Michael Smith

“It’s really getting hot” I said as we waded through shallowpools under a blistering sun. The white limestone reflectedsunlight back up from the ground, making a sort of naturaloven with heat radiating from all directions.

“Yeah,” my friend answered, “Where are the deeper and coolerpools in this creek?” Not only was it a fairly shallow creek, butthe sun was also drying the pools and making them shallower.As a result, the water in some places was getting close to thetemperature you would want for a good soak in the bathtub.

There we were, making our way along a very hot creek whiletrying to maintain our optimum body temperature of98.6˚F. Our bodies have a very narrow range in whichthey can function well, so we have to have ways of warm-ing when it’s cold and cooling when it’s hot. We are en-

dotherms, meaning that we generate body heat to keepwarm and use other strategies to keep cool, maintaininga nearly constant temperature. Getting too hot may resultin “heat exhaustion,” with such symptoms as dizziness,nausea, and feeling faint. If we get even more overheat-ed, our body’s ability to regulate temperature may fail sothat we stop sweating, become very hot, and may die. Inthe field on hot days, we need to be careful to bring wa-ter and make use of shade and rest so that we avoid heatillnesses.

So what about the snakes, turtles, and frogs we were lookingfor? Can they suffer from the heat? Absolutely! Reptiles andamphibians are ectotherms, meaning that they generate littleheat within their bodies and their temperatures tend to matchtheir surroundings. They can do OK within a range of temper-atures, but they cannot function well if their body temperaturegets outside that range. And if it is too hot or too cold, they

will die. How do they manage to stay within a certain range oftemperatures, if they are “cold-blooded”?

Let’s look at one of the water snakes living in that creek. Whileit could hunt and move about easily in the morning when thetemperature was in the 80s, later in the day it would makemore and more use of shelters from the heat. As the rocksbecame hot to the touch, the snake could find spaces under-neath some of the bigger rocks where it was cool. Although itcould not sweat in order to cool off, its body would lose heatto the cooler underneath side of the rock. Back within its besttemperature range, the snake would venture out to one of the

pools and hunt for fish, but the pool of warming water and thebright sunshine might gradually drive the snake’s temperatureback up. At some point it might find a ledge along the edge ofthe water, or a tunnel back into the cool earth, escaping theheat again. During the hottest part of the summer, the watersnake may rest within such tunnels or deep crevices through-out the day, coming out only at night to hunt food.

Blotched water snake

Frog Calls July, 2013

Page 4

In the mild Texas winters, the snake could have been activefrom time to time on warmer days. Early in the morning, thatsnake might poke its head out from its hiding place and intothe sun, to begin warming. The snake would be cool – notdangerously cold but cool enough that it might be sluggishin hunting and unable to shift into high speed to get awayfrom a predator. As the sun warmed the snake’s head, thecirculating blood would carry heat to other parts of its bodyuntil it warmed enough to emerge intothe sun. The little reptile might flattenits body, exposing more of its surfaceto the sun and warming further. In thisway, it reaches a temperature that stillmight feel cool to us, but would bewarm enough to move quickly and useits reptilian brain to interpret cues in itsenvironment and decide where to goand what to do.

Reptiles have a variety of ways to regu-late their temperature, including usingthe sun to warm themselves and get-ting away from the sun to cool. Some snakes shiver (usemuscle contractions) to raise body temperature just a little bitwhile coiled around a clutch of eggs. Some reptiles can shifttheir color to become darker and absorb more sunlight.Once warmed, they may shift to a lighter color so that moreof the sun’s energy is reflected away. If they become stressedin extreme heat, many reptiles may pant, bringing cooler airacross the moist tissues of the mouth and losing some heatthat way.

Even though reptiles have a number of creative ways to reg-ulate their temperature, they are still limited in what they cando during very hot or cold times and must rely on environ-ments that offer lots of shelters and places to warm up. Isthere anything good about being an ectotherm? Does cold-bloodedness have some advantages? The answer is definite-

ly “yes.” Think about the energy that is required for our bod-ies to do what they do. Muscle movement takes energy, asdoes the activity of all the internal organs. Our bodies arelike little engines that are constantly breaking down the foodthat we eat in chemical reactions that provide us with ener-gy. These chemical reactions are our metabolism. As endo-therms, our engines are running at a pretty high rate all thetime because we not only need energy for activity, we need

it to maintain our internal temperature.Reptiles, amphibians, and other ectothermsuse food energy primarily for activity, andthey can use sunlight and warmth fromtheir surroundings to maintain a workablebody temperature. Our water snake usedthe sun to raise its temperature when it wasactive, and when inactive in a shelter it didnot need to use its internal energy reservesbecause it did not need to stay warm. Dur-ing nighttime activity it still indirectly madeuse of the sun’s energy, getting warmthfrom the rocks and water that werewarmed by the sun the previous day. A

human might need ten times more energy than the watersnake, meaning that the reptile can get by on much lessfood than the mammal.

As we finished our day at the creek, we turned a big rockand found a blotched water snake coiled beneath. He wasnot pleased about being caught and examined, and he let usknow just how displeased by the usual tactics of biting anddischarging musk (they are nonvenomous and the bites justleave small scratches; the musk, however, is a bad smell thatstays with you much longer than the pain of the bites!).Knowing how hot it was, we replaced the rock and madesure to release the snake back into his cool refuge. Even abad-tempered water snake should not have to flee for its lifeover hot limestone rocks.

A Water Snake Copes with Summer Heat (continued)

Frog Calls July, 2013

Page 5

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 andhaving fun. And we do it without charging anything (but we gladly accept tax-deductible contributions to keep usgoing). We are a 501(c)(3) nonprofit organization - please visit us on the web at: http://crosstimbersconnection.org.

Michael Smith, President - michael@crosstimbersconnection.orgMark Pyle, Vice President - markpyle@crosstimbersconnection.orgDebbie Dorman, Secretary/Treasurer - ddorman@crosstimbersconnection.orgRob Denkhaus, Board Member

P.O. Box 151882 v Arlington, Texas 76015

Please visit Crosstimbers Connection on Facebook!

How to go on a free outing with us:

Contact us to plan an individualized outingWe work with small groups, schools, clubs, or families to plan a specific date and location foran unforgettable experience in nature. Just contact us at: contact@crosstimbersconnection.org

The Skink RefugeThis five-lined skink made gooduse of a hollowed-out section of asupport post along the marshboardwalk at the Fort Worth Na-ture Center & Refuge. This younglizard would retreat back into thepost anytime someone camenear, but at other times wouldemerge into the sunlight, heatingup and getting ready to hunt forits next meal.