Frog Calls, December 2014

Frog Calls December, 2014

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Frog Calls

Newsletter of Crosstimbers Connection Volume 2, No. 4 f December 2014

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We will jump right into the New Year with a presentation about where the reptiles and amphibians go when it gets

cold. Michael Smith will be at the Fort Worth Nature Center & Refuge with lots of pictures and slides to talk about

how these animals seek out refuges when it gets too cold. Snakes, lizards, turtles, frogs, and their kin choose all

kinds of places to shelter from the cold, from mammal burrows to the bottoms of ponds. Some become active

during warm, sunny days in the winter. The salamanders even prefer wintertime after it rains; this is their season for

breeding. After we talk about this and look at pictures, we may take a walk if the weather permits, looking for

some of the refuges where these animals may be hibernating, and maybe even seeing a few turtles sunning or

skinks scurrying through the leaf litter.

(You can help make it happen)

2015 Should Be a Great Year!

January 3: The Lizard in Winter Reptile & Amphibian Hibernation


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Then, in March we will talk about some of

the fish found in the West Fork of the

Trinity River. Nic Martinez will give us a

great introduction to some of our native

fish. See which of them hang out near the

surface and which ones lurk in deeper

places. This presentation will feature

interesting facts about the fish and we

will look at photos and talk about how to

identify them, learning what separates

the shiners from the sunfish!

Field Trips

The year would certainly not be complete without some field trips. We plan to schedule a series of “herp walks” at

the Fort Worth Nature Center & Refuge as spring gets under way. We would also like to plan some outings at

other locations around the greater metroplex area, perhaps at the LBJ National Grasslands near Decatur or some

other spot.

Where do you want to go? What would you like to see and maybe photograph? We would love to hear from you

and start making plans for outings in 2015. You can email us at [email protected] or fill out the

contact form at our website.

2015 Should Be a Great Year!

March 8: Fish of the West Fork of the Trinity River

January 3, from 2 to 3pm: The Lizard in Winter – This is the program as described on page one. The first part takes place at the Hardwicke Interpretive Center, and if weather permits we’ll take a short walk to several locations (which could push the time out to around 4pm). March 8 (Sunday), from 2 to 3pm: Fish of the West Fork of the Trini ty River – This is the program described above on this page, and it takes place at the Hardwicke Interpretive Center. (While Crosstimbers Connection does not charge a fee, there is an entrance fee to the nature center-see their website, www.fwnaturecenter.org)

Don’t Miss Out! Our next programs at Fort Worth Nature Center & Refuge


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The seasons have definitely changed in north Texas, even if we still have occasional sunny and fairly warm days.

Cold weather came to visit as early as November 12th and 13th with high temperatures in Decatur never getting

out of the 30s and nighttime lows well below freezing. But then, by the end of the month, sunny days in the high

70s returned to remind us that it was still fall, not yet winter.

Those of us who like to see reptiles and amphibians (“herps”) know that they mostly disappear after freezing

weather arrives in the late fall. When the weather gets cold, many herps find refuges from the cold and may stay

inactive until next spring or may only come out for limited activity during warm spells. Being “cold-blooded”

means that they are at the mercy of the temperature around them, and they must find refuges that will remain

above freezing. ‘Tis the season for hibernation.

When we think of hibernation, what we picture may be a bear in a cave, sleeping through winter. Hibernation is a

period in which bodily activity and metabolism slow, body temperature typically drops, and the animal is dormant.

Since reptiles and amphibians are cold-blooded (ectothermic), it is a given that their body temperature will drop in

colder surroundings. Their metabolic rate also slows during cold winters. However, they continue to show some

activity, moving about and drinking.

Because herps cannot control their body temperature independently of their surroundings, their wintertime

slowing and cooling seems to some people like a different process than that shown by mammals such as bears

and rodents that hibernate. Because of this, in 1965 Wilbur Mayhew proposed the term “brumation” for the

horned lizards he was writing about in the journal Comparative Biochemistry and Physiology. The term has caught

on, but others have pointed out that the term “hibernation” does not specify that the animal in question must be

warm-blooded, and so it seems equally applicable to ectotherms. And so, I’ll just use the term “hibernation.”

On November 28 I spent the afternoon wandering around several spots at the LBJ National Grasslands, north of

Decatur, checking the temperature several inches below the surface of the ground or water. I had obligated

Escaping the Winter Cold The Insulating Blanket of Soil & Rock

-- by Michael Smith


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myself to present a program on hibernation in reptiles

and amphibians, and figured I should do what a

naturalist ought to do when planning such an event: get out, observe what’s going on, and take some notes. If I

was going to talk about some of the places where these animals seek refuge from winter cold, it would be helpful

to go see what the temperatures were under the ground, under rocks and logs, and under the water. I wanted to

do this several more times, to see how these temperatures change as it gets colder.

At my first stop, on top of a ridge where grasses and forbs grew, interspersed with a few prickly pear cacti, the

wind blew my hat away as I tried to push a cheap garden trowel into hard-packed sandy soil. Once I could put the

temperature probe down about five inches, I covered it with the soil I had dug out and placed a second

thermometer on the surface of the ground to compare the temperature there with the temperature five inches

down. I shaded the surface thermometer with my backpack to get a more accurate reading, and waited. At

12:52pm, the temperature was 70°F at the surface and 54.4°F down in the soil. This made sense; it was a

particularly warm day and there had been several days of hard freeze a couple of weeks ago. The surface had

warmed up these last few days but the lower layers had not had time to get warmer.

A couple of miles from there, still along that

same ridge, I sampled the soil in an oak motte.

Within this small group of oak trees, the soil

was mostly shaded and mixed with some leaf

litter. Here, the surface temperature was 68°F

and about five inches down it was 53.4°F. Just

a few steps away, I sampled the temperatures

under a big chunk of walnut shell limestone.

“Walnut” seems an odd way to talk

about this stone that looks like a mixture

of little oyster shells with just enough

cement to stick them together into rock.

Some of the ridges at LBJ Grasslands

are dominated by big slabs of these

fossil shells. In previous years at this

location, we have found a juvenile

speckled kingsnake, and on another

occasion a chorus frog, and frequently

we find the striped bark scorpion under

these blocks of cemented oyster. The

Escaping the Winter Cold

Checking temperature under the rock at the lower left, with the thermometer probe wire visible, running out from under the rock and toward the backpack


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rock that I chose on this day was about two-and-a-half

feet square and six inches thick. Underneath, the

temperature was 46.5°F. Even the surface temperature was a bit cooler here, at 62°F.

So far, the developing theme seemed to be that the temperature under a few inches of soil or rock was about 15

degrees cooler than it was on the surface, reflecting the fact that soil and rock provide some degree of insulation.

At this point it seemed to be insulating against the warm-up that had been going on for the previous couple of

weeks. It was time to see if that would also be the case in the very sandy soil of a nearby open savannah and

woodland that I’ve walked many times in the past.

As I reached that spot, the sun was shining brightly and it was warm and comfortable at 1:59pm. At the first place I

stopped, it was 54.7°F about five inches down into the sandy soil, and yes, this was just under 15 degrees cooler

than the temperature on the surface. I then spotted a couple of gopher mounds, and since gopher burrows can

make excellent hibernation spots for a variety of reptiles and amphibians, I was eager to check them out. As I

dumped scoops full of sand, a small toad-like creature tumbled out of the trowel. It turned out to be an adult

Strecker’s chorus frog, luckily uninjured

and soon alert and hopping around. This

little frog had probably dug in during the

cold spell and might have stayed there for

some time, had I not disturbed him. I

sampled another, undisturbed gopher

mound a foot or so away, finding the

temperature to be 55.4°F. At the surface

it was 68°F.

I walked further into this meadow, past

some cattle that looked up in idle

curiosity at this two-legged visitor to their

grazing spot. I reached a belt of oak and

juniper woodland, and wandered back through some saplings into a spot with somewhat more mature growth.

There in the dappled sunlight, moss grew on the woodland floor amid a thin layer of fallen leaves. Digging down, I

found that the temperature five inches down was 48.9°F while at the surface it was 64°F. Once again, about 15

degrees difference.

The afternoon was passing and the sun rode lower in the sky, and I wanted to visit at least one other location. I

checked on a small pond toward the northern border of the grasslands, to see if the rains we received in the past

month or so had filled it at all. Sure enough, although clearly not full, the pond did have water in it. And the cricket

frogs had taken full advantage of this fact, no doubt eating large numbers of the tiny invertebrates found around

the water’s edge. At my approach, the cricket frogs scattered like grasshoppers jumping out of the way, one here,

a couple there, and still more at the edge of my vision. Many of them jumped into the water and then swam back

a little toward the shore, digging into the leaves and algae along the bottom. Although I was not prepared to

sample the temperature at the middle of the pond, I could toss the thermometer’s probe out into the water that

appeared to be about six inches deep. The temperature there was a pretty mild 57.4°F, while the thermometer

resting in shade on the bank read 77°F.

Strecker’s chorus frog



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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

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Walking around the pond, I spotted a bigger frog

sitting in shallow water, with big bright eyes

surveying the scene. Along this leopard frog’s

back, dark brown spots were scattered on a

splash of green background. Bordering this were

light cream-colored dorsolateral folds, running

like racing stripes down each side of the body.

This beautiful frog was a great way to finish a

wonderful, warm fall day at the grasslands. When I

got to the shaded side of the pond, I found that

the water was 54°F about four to five inches

down, while the bank was 69°F. The cricket frogs

seemed just as active in the shade as they had been in the sun.

Between 12:52 and 3:17pm I had sampled several locations and found temperatures about four to six inches

below the surface of soil, water, or rock to be around 15°F cooler than temperatures at the surface. The only

exception was the banks of the little pond, in full sun, where the surface temperature was a little higher.

In the coming weeks I wanted to measure temperatures again, as the season turned

colder. As the air and surface temperatures became cold, I expected that the insulating

layer of soil, rock, or wood would result in warmer temperatures in deeper places where

reptiles and amphibians seek refuge from winter.

On December 21st, a cold and cloudy, slightly misting day, Johney Buckley and I took a

walk at the Fort Worth Nature Center & Refuge. We found that it was a little warmer

under some shelters than it was at the surface. On the Caprock Trail, in a burrow under

a huge slab of walnut limestone it was 46.2°F inside, while it was about 4-and-a-half

degrees colder just outside the burrow. In a bottomland forest, we found an opening

under a small tree, perhaps where something had burrowed beneath the roots. The

temperature was 47.5°F under the tree, but 43.8°F on the outside at the base of the

tree. We also dug under about an inch of leaf litter and down about six inches into the

soil. We found that the temperature there was 45.0°F while on the surface it was 42.6°F.

As the temperatures at the surface had fallen, the soil and rock were doing what they

always do, serving as insulation to trap a little heat where animals such as reptiles and amphibians can find a

shelter from winter’s cold.

Leopard frog


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Frog Calls, December 2014