RRN Newsletter 21

RIPARIAN NETWORK NEWS Riparian: transitional area adjacent to a waterway Uplands: land lying above the 100-year floodplain No. 21, July 20, 2020 What is That Sound I Heard Last Night? Are you hearing a lot of noise these nights and wondering what’s making that racket and why? If it’s not caused by humans, it’s very likely either a frog, a toad, an insect or a bird. And why are they disturbing the quiet of the evening? There can be a number of reasons depending on the situation and the species including attracting a mate, claiming territory, warning others of danger, etc. Especially on a moonless night, sound may be the only way for males to signal to females of the same species that they are available and ready to do their part towards the survival of the species. If it is an insect you are hearing, likely it’s either a cicada or a katydid. At night it is more likely the later since cicadas generally sing during the day or at dusk, katydids later in the night. Owls don’t all “Whoo,” but a bird sound is most likely an owl, a nightjar, such as a Chuck-will’s- widow, or perhaps an enthusiastic mockingbird. However, if you live near water or even just have a puddle nearby, chances are what you hear is either a frog or a toad. Frogs and toads are amphibians, which literally means two lives because of the metamorphosis they undergo. Frogs and toads are generic names, and, in general, species that are called toads are more adapted to arid conditions. However, in reality, throughout their lives all amphibians are linked to water. Amphibians lay their eggs in water (or at least in moist microhabitats). When the eggs hatch in water, the young larvae are more fish-like than frog-like, with gills for breathing and fins for swimming. The eggs pictured on the right are those of a Texas species on the verge of extinction, the Houston Frog, Anaxyrus houstonensis. Legs and lungs develop and fins disappear during metamorphosis. Even though adult frogs and toads might spend more time on land, they remain linked to water. Amphibian skin is special in that it is permeable to water. So instead of drinking water, frogs and toads simply absorb moisture through their skin. Most frogs simply jump in the water when they are thirsty. That explains why they tend to live as adults in or close to water. Treefrogs can absorb water through their underbelly by clinging to the side of a tree which explains their name. Likewise, toads will settle into a muddy spot to absorb water through their underside. Moist environments also help adult amphibians breath through their skin and mucous membranes in addition to using their lungs. Amphibians are key indicator species. When amphibians go extinct or experience significant reductions in population, it is usually a sign that the entire ecosystem is in danger. Habitat destruction, non-native species (predatory fish, bullfrogs, fungus, pathogens), climate change (alters air temperature and water levels), pollution and diseases (especially chytridiomycosis, caused from the chytrid fungus) all have been shown to contribute to amphibian declines worldwide. There are forty-two species of frogs and toads in Texas. One, the already mentioned Houston Toad, is endangered, four others are threatened and one is extirpated meaning it hasn’t been seen in our state for a quite a while. Want to know more about the frogs and toads you might see or hear in the Wimberley Valley? Here are some of the most common: American Bullfrog - The largest of all North American frogs, American Bullfrogs (Lithobates catesbeianus) are normally 3 1/2 to 6 inches from head to tail. But they can get as big as 8 inches and weigh up to 1 1/2 pounds. This is the kind of frog made famous in frog jumping contests or that you might find on your dinner plate if you are so inclined to order frogs legs. Bullfrogs are a member of the “True Frog” family and are nearly always found near permanent water. They lay their eggs in a film that floats on the water. The bullfrog’s distinctive sound reminds some of a cow and thus its name. Others describe it as what you might hear if someone blows over a large jug. Native to the eastern and southern U.S. with Texas on the western border of its native habitat. But as early as 1898, the bullfrog was introduced in new places given its popularity on the dinner table. Bullfrogs eat just about anything they can fit into their large mouths - birds, rats, snakes, lizards, turtles, fish, other frogs, even smaller frogs of their own species. In Texas as well as other places where they are native, predators such as herons and egrets, large water snakes, alligators, and snapping turtles keep adult bullfrogs in check, while fish gobble down tadpoles. But outside its native range, effective predators may be absent. Thus in the western U.S. and other parts of the world, bullfrogs are often considered an invasive species. Leopard Frog - Leopard frogs are a lot smaller, 2 to 4 inches long. And they look like their name suggests - they have spots! These members of the true frog family were the ones you might have dissected in high school biology. Leopard frogs are also are found near permanent water and lay eggs in large translucent clumps. At one time it was thought all leopard frogs in the U.S. were part of the same species, but they are not. The ranges of two types of leopard frogs overlap in Hays County - Rio Grande (Rana berlandieri) and Southern (Rana sphenocephala). Leopard frogs have a distinctive raised ridge as illustrated in the Rio Grande leopard frog shown on the right. Referred to as the dorsolateral fold, the visual difference between the two Hays County species is how this line varies as it approaches the hind legs. Another more distinctive difference is the sound they make. The Rio Grande leopard frog even sounds like a big cat purring or growling. The Southern Leopard Frog sounds more like Woody Woodpecker. Tree Frog - Two types of tree frogs are found in the Wimberley Valley - The Gray Treefrog (Hyla chrysoscelis) and the Cope’s Gray Treefrog (Hyla versicolor). The two species are hard to tell apart except for differences in their call structure. Though both sing a short trill, the Grey Treefrog’s call is slower and more melodic rarely exceeding 34 trills per second. Treefrogs are primarily nocturnal and spend most of their time in trees or shrubs close to the water, descending only to breed. They lay single eggs attached to vegetation. Both species are relatively small - 1 1/4 to 2 inches long and primarily eat insects found in trees such as caterpillars, beetles, flies, crickets, and other small invertebrates. A third species, the Green Treefrog (Hyla cinerea), is found around Aquarena Springs in San Marcos and in other places on the eastern side of Hays County. Cricket Frog - Only 5/8 to 1 3/8 inches, the Blanchard’s Cricket Frog (Acris blanchardi) is a smaller member of the treefrog family. Their color varies ranging from light gray to greenish-brown, with splotches of gray, red, or green in the middle of the back common. Cricket frogs are fairly common in the Wimberley Valley and are active both during the day and at night. They generally stay close to aquatic environments and are good leapers. During most of the day, they generally stay under the cover of vegetative debris or hidden in grasses. But they can also be seen basking in full sun. If you hear a small splash as you are walking along a stream, you likely startled a cricket frog. At night, it’s easy to recognize their distinctive call often described as the sound you make when you click two marbles or two rocks together. TrueToads – True toads are recognized by their plump bodies and short legs. Amphibians found in this group are adapted to exploiting somewhat drier habitats. They have dry, warty skin that excretes a toxin that helps protect them from predation, though they are only mildly irritating to humans. If you find a toad in your flowerpot, it is most likely a Gulf Coast Toad (Incilius nebulifer), the most common toad species in this area. These medium sized toads are generally 2 to 5 inches long. The color of their back varies from nearly black to shades of brown and grey. A distinctive white or yellow stripe runs down their middle back. The Gulf Coast toad’s head has two distinct cranial crests behind their eyes with a “valley” between the two ridges. You can distinguish a Gulf Coast Toad’s sex by its throat color - the male’s is yellow/green, the female’s is not pigmented. This toad has clearly adapted to suburban environments. In the heat of the summer, these toads are often seek out shallow water to keep cool thus its presence in freshly watered pots. At night, you might see them underneath an outside light searching for insects. Frogs/toads are an important component of riparian ecosystems and, as such, are excellent indicators of their health. Permeable skin makes them especially sensitive to toxic substances. At the egg stage, chemical pollutants in the water can cause a variety of developmental abnormalities. They are also an important link in riparian food chains. As tadpoles, they eat algae and as adults consume a lot of insects including mosquitos both adults and larvae.

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