Breaking Slumber

 

Many small creatures awaken in Spring

In the winter months in central Texas, most cold-blooded reptiles and amphibians exhibit a form of hibernation called brumation. Triggered by shorter days and lower temperatures, this state can last for days or weeks, depending on the species. Brumation differs from true hibernation in that these animals remain semi-conscious and occasionally wake up to drink but not eat. During this period, body temperature, heart rate, and respiratory rates are greatly reduced.  This state of dormancy occurs with several common amphibian species, including the Rio Grande Leopard Frog (Lithobates berlandieri), Gulf Coast Toad (Incilius nebulifer), and Green Tree Frog (Hyla cinerea).

Rio Grande Leopard Frogs are medium-sized native frogs, to 4.5 inches, greenish-brown in color with a yellowish ridge along each side of the back. They have large dark spots on the back and sides, and a wide, light-colored jaw stripe that is poorly defined and fades in maturity. Their call is described as a short, low-pitched guttural rattle, either given singly or in rapidly repeated sequences. These frogs spend the winter months resting at the bottom of ponds, lakes, or other bodies of slow-moving water, but can become active during warmer, wet periods. Since they are semi-aquatic, they can also tolerate cold conditions by burrowing into mud or soil. They tend to enter brumation just before freezing weather, and often hide in deeper water to temporarily escape extreme temperatures.

Rio Grande Leopard Frog

The Gulf Coast Toad is a native, broad-headed, mostly terrestrial toad, to 5 inches, with prominent cranial crests that form a depression on top of the skull. Their background color is brownish-yellow to brownish-gray, with broad dark lateral stripes bordered by a light stripe, as well as a light central stripe, and they are covered in numerous small whitish to orange spots. Their vocal sac becomes large and rounded when calling, which sounds like a short, flat trill repeated several times. These toads are usually dormant from December to February, hunkering down in self-dug holes, abandoned animal burrows, under logs, or in leaf litter to protect themselves when the temperature dips below freezing. While they become active as the temperatures rise in early spring, they may also burrow to survive hot, dry conditions in the summer months, and this unique behavior is called aestivation.

Gulf Coast Toad

Green Tree Frogs are smaller, native arboreal frogs, to 2.5 inches, with smooth skin, a slender, flat body, and long slender legs with large toe pads on each foot. In warmer conditions, when the frog is active, they are typically a bright green color, but they can change to a dull color during periods of cool weather or to blend in with their surroundings. They also have a long white stripe on either side of the body. Their call sounds vaguely like a honking duck and is repeated 30 to 60 times a minute. These frogs brumate in the winter months, often hiding under deep leaf litter, in tree cavities, in potted plants, or even in the corners of garages and sheds. During this time of inactivity, they slow their metabolism and sometimes survive partial freezing by producing natural antifreeze compounds called glycerol that protect their cells. They also typically choose sheltered damp spots to avoid freezing completely, and may wake on warmer, sunny winter days to move about.

Green Tree Frog

As the days get longer and temperatures begin to rise, once again we will be treated to the sights and sounds of these marvelous amphibians, as they break their winter slumber!

Poisonous or Venomous?

Poison Ivy

Often used interchangeably when describing some plants and animals, in reality poisonous and venomous mean two different things.  Poisonous describes plants or animals that are harmful when consumed or touched.  Venomous refers to animals that inject venom into their prey, by means of a bite or sting, when hunting or for self-defense.  To add to the confusion, all venoms are a poison but not all poisons are venoms!

Poisonous species typically produce a toxin that can range from irritant to fatal. Plants such as Poison Ivy (Toxicodendron radicans) and some members of the Spurge family are considered irritants when they come in contact with skin, but this effect is produced through different mechanisms.  Nearly all parts of the Poison Ivy plant contain urushiol, which is a substance that gives us contact dermatitis, or a severely itchy and painful inflammation of the skin.  

Texas Bull Nettle

Spurges such as Texas Bull Nettle (Cnidoscolus texanus) and Betonyleaf Noseburn (Tragia betonicifolia) have raised structures called trichomes that are capable of ’stinging' animals and humans that brush against them.  These plants have trichomes on their leaves and stems that have bulbous tips that break off and reveal needle-like tubes that pierce the skin. They can cause an itching, burning rash by emitting onto the skin a mix of acetylcholine, formic acid, histamine, and serotonin.  

Jimsonweed or Sacred Datura

One local native plant, Jimsonweed or Sacred Datura (Datura wrightii) goes well beyond irritant to hallucinogenic and even fatal if ingested.  All parts of this plant contain toxic alkaloids, and the narcotic properties of this plant have been known by humans since before recorded history.  They once figured prominently in important religious ceremonies of various southwestern Native American tribes.

Gulf Coast Toad

Animals that are poisonous include most amphibians (frogs, toads, salamanders, and newts), that have some amount of toxins on their skin and within other tissues. Special skin glands produce useful proteins, some for use in respiration, others for fighting bacterial or fungal infections, and at least one in each species that is used for defense.  For example, many toad species will release their toxins when they feel threatened, such as when they are caught by a dog or cat, and can trigger drooling, vomiting, and respiratory or cardiac problems.

Western Diamondback Rattlesnake

While some snakes are the most commonly known venomous animals, all spiders, some lizards, and many bees, ants and wasps are venomous as well.  The venoms they inject through a bite or sting contain various classes of toxins designed to perform specific biological effects such necrosis or death in multiple cells (necrotoxins) or individual cells (cytotoxins), disruption of the nervous system (neurotoxins), or damage to muscle tissue (myotoxins).   The venom of our Western Diamondback Rattlesnake (Crotalus atrox) carries both necrotoxins and myotoxins, Black Widow spiders (Latrodectus macrons) carry both neurotoxins and cytotoxins, and Striped Bark Scorpions (Centruroides vittatus) and Texas Redheaded Centipedes (Scolopendra heros) carry neurotoxins.

Striped Bark Scorpion

Texas Redheaded Centipede

While the vast majority of snake toxins are transferred by bite, one exception includes garter snakes (Thamnophis sp.), which are small and harmless in terms of their bite but are toxic to eat because their bodies absorb and store the toxins of their amphibious prey.  In our area, these snakes include the Black-necked Garter Snake (T. cyrtopsis) and the Western Ribbon Snake (T. proximus).

Western Ribbon Snake

It is important to keep in mind that many plants and animals that are poisonous or venomous are not necessarily a guaranteed threat to humans, as much depends on how the plant or animal is encountered, its toxicity level, and the amount of toxin absorbed.  Regardless, respecting these species and giving them their space is the cardinal rule.  Interestingly, the medicinal use of venoms for therapeutic benefit in treating diseases dates back to 380 B.C. in ancient Greece.  Today, the venoms produced by different organisms, which contain hundreds of different bioactive elements, are isolated, purified, and screened, then studied to identify components that may have desirable therapeutic properties.  This research is often the starting point for developing a therapeutic drug, and those types of drugs on the market today are used to lower high blood pressure, relieve severe pain, act as blood thinners, treat Type 2 diabetes, and stop bleeding during surgical procedures.