Snakes of South Central Texas

Excerpted by Gary Poole from this linked article authored by Sal Scibetta. All photos were taken by Sal Scibetta unless otherwise noted.

SNAKE BIOLOGY AND PHYSIOLOGY

All snakes have basically the same body plan and all are carnivores. Snakes are well known for their unique methods of feeding. Venomous snakes inject venom into their prey while non-venomous snakes are mainly constrictors.

Snakes are highly modified lizards and, like the vast majority of reptiles, are ectothermic poikilotherms. This means their variable body temperature is determined by the environment.

THE ROLE OF SNAKES IN ECOSYSTEMS

Snakes play a very important role in ecosystems. They are typically in the middle of the food web, being both predator and prey. They are predated on by birds of prey, coyotes, raccoons, opossums as well as feral cats and hogs. As predators, and depending on their size and environment, snakes eat rodents, worms, insects, crayfish, fish, frogs, birds, and eggs.

MOST COMMON SNAKES IN BEXAR COUNTY

The result of Bexar County’s ecological diversity is that we have many different species of snakes. This Talking Point will highlight the most common but is by no means exhaustive.

NON-VENOMOUS SNAKES

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Eastern Hognose (Heterodon platirhinos) When first disturbed the Hognose Snake will flatten out their neck and hiss ferociously, often striking with a closed mouth. If this threat display fails, they are renowned for their ability to “fake death” often turning upside down with mouth agape. These are technically venomous snakes with fangs in the back of their mouth and very weak venom. Worst case bites are very uncommon and usually just produce localized swelling. Hognose snakes are mainly predators of toads.

Rough Earth Snake (Haldea striatula): This is a very common snake, often found in suburban lawns and flowerbeds. These snakes are completely harmless, reach a maximum length of only 10 inches, and eat worms, grubs and other small insects.

Checkered Garter Snake (Thamnophis marcianus): The Checkered Garter Snake is commonly found in both suburban and undeveloped areas. Usually found near water, they prey on frogs, rodents, and invertebrates. They can reach two feet long.

Western Ratsnake (Pantherophis obsoletus) (also Texas Ratsnake or Chicken Snake): The Western Ratsnake is the most common of several local species. This snake is often found in chicken coops eating  the eggs and chicks. This is one of the largest snakes in Texas, up to 6 feet but they can get larger. They are common bird predators but also eat mice, rats, and squirrels.

Diamondback Watersnake (Nerodia rhombifer) and Blotched Watersnake (Nerodia erythrogaster transversa): Very common in South Central Texas, these two snakes are often confused with Cottonmouths. These snakes are very defensive exuding a foul smelling musk. Watersnakes eat mainly fish and frogs.

Rough Green Snake (Opheodrys aestivus): In Central Texas, this snake is easily identifiable as a small, thin, bright green snake up to three feet long. Commonly found in brushy areas, these once common snakes are becoming hard to find. Green Snakes eat mainly insects, especially grasshoppers.

Texas Patchnose (Salvadora grahamiae lineata): The Texas Patchnose is more commonly found in rocky areas north of the Balcones Escarpment but they can be found throughout South Texas. They have a brown striped body and enlarged rostral (nose) scale. Adults reach 2-3 feet and are fairly slender. Patchnose snakes are opportunistic feeders eating, lizards, snakes, eggs and rodents.

VENOMOUS SNAKES

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Texas Coral Snake (Micrurus tener): Coral snakes are a highly venomous elapid (a family of venomous snakes characterized by their permanently erect fangs at the front of their mouth.) related to Cobras and Mambas. They are quite common in San Antonio. The majority of the Coral Snake’s diet is other snakes. While they are typically not defensive, they do have a powerful neurotoxic venom that can cause severe breathing difficulties. They are not typically seen as deadly but keep in mind there is an extremely limited supply of antivenom available for these snakes.

Western Diamondback Rattlesnake (Crotalus atrox): This is the most dangerous snake found in this area. They are very defensive snakes and may, but not always will, rattle before striking. Up to 4 feet long in the San Antonio area, this snake reaches 6 feet or more further south. They feed mainly on mammals such as mice and rabbits.

Broadbanded Copperhead (Agkistrodon laticinctus): This snake is more common north and east of South Central Texas. Their bites are usually not life-threatening but can cause significant tissue damage that may require hospitalization. While they primarily eat rodents, they are also known to eat invertebrates. Copperheads are known to swarm areas where they eat emerging cicadas.

Northern Cottonmouth (Agkistrodon piscivorus): Common east of here and along the coast, Cottonmouths are not very common in the San Antonio area. They prefer slow moving or still, murky waters. These snakes are not aggressive but are very defensive. They will stand their ground but do not chase people. Cottonmouths will eat pretty much any animal matter, are known to be cannibalistic, and one of the few snakes documented to eat carrion.

WHAT TO DO IF YOU ARE BITTEN BY A VENOMOUS SNAKE

A venomous bite is extremely painful. The pain can be instantaneous or slowly increasing within minutes. You can also tell a venomous snake bite because of the two larger holes. A nonvenomous snake bite will have 2 rows of small punctures. If you are bitten by a venomous snake get to a hospital as quickly and calmly as possible. The best first aid kit for snakebite are car keys and a cellphone.

The University of Maryland Medical Center recommends:

• Call 911
• Wash the area with soap & water
• Immobilize the bitten area lower than heart
• Use a cool compress
• Put a loose bandage above bite to slow venom but only if it will take >30 minutes to get to hospital

For additional material for children see Leapin’ Lizards by Wendy Drezek, AAMN.