Reptiles (Class Reptilia)
The reptiles’ dry scaly skin distinguishes this group from amphibians. In snakes, these scales are not like fish scales, which are separate and detachable, but are part of a continuous sheet that is shed when the snake grows larger than its skin. The brille, also called the ocular scale or spectacle, is the membrane that covers the eye; the brille turns blue or cloudy when the snake is ready to shed its skin.
Males and females in most species of reptiles differ from one another by size, shape or color. These differences allow individuals to choose a mate based on their "preferences" and likely perceived success in breeding. Temperature and daylight length can also affect breeding. Most reptiles reproduce sexually, however, some species of rock lizards and whiptail lizards reproduce parthenogenically, meaning females reproduce without a male. This breeding system results in only females being born, each one essentially a clone of the mother.
Lizards, snakes, and aquatic turtles have eggs with pliant shells, while crocodiles, geckos, and tortoises have hard, calcified shells. Offspring sex in turtles, tortoises, and some crocodiles is dependent on temperature surrounding the eggs at particular stages of incubation. Parental care of the eggs and young are most developed in the crocodiles. (No, we do not have crocodiles or alligators or caiman naturally occurring in Maryland.)
Turtles and Tortoises (Order Testudines)
244 species worldwide, 19 species in Maryland
Turtle shells are comprised of 59-61 bones with the shell on the back or dorsal side called the carapace and the shell on the bottom or ventral side called the plastron. The shape of the shell gives hints on the life cycles of these animals. Land turtles have domed shells, which help protect the turtle from being crushed by predator jaws. Aquatic turtles are more streamlined for swimming, as they have lower water resistance. Mud turtles and bog turtles have hinged plastrons, which allow them to retreat into the shells and close up. The growth of turtles and their shells varies even within the same clutch due to habitat, temperature, rain, sun, and amount and type of food. Scales on a turtle shell are called scutes and give an idea of how old the turtle is. Growth rings similar to tree rings will show on a scute; this is not a precise method but it will get you in the ballpark. Growth rates of the scutes are slowed during winter.
Tortoises are land turtles and are the Methuselahs of the reptile group. Some tortoises can live 200 years in captivity and box turtles can live to be 100 years in the wild. By contrast, aquatic turtles have lived 40-75 years in captivity.
Telling the difference between male and female turtles can be tricky. In general, males have longer and thicker tails and a concave plastron. The female plastron is usually flatter. A female will lay her eggs in many different places, including decaying vegetation, leaf litter, nests of other animals, or in burrows dug by the female herself. On average, eggs hatch within 2 months in temperate regions, and 4 months in tropical regions. Most turtles feed on vegetation or slow moving prey such as mollusks, worms, and insect larva.
Lizards (Order Squamata, Suborder Lacertilia)
3,751 species worldwide, 6 species in Maryland
Lizards have 4 legs with 5 toes each and well-developed tongues that are used to sense their environment. Their tongues detect chemical cues from food, mates, territories and predators. Biologists think that the pineal body helps regulate their biological clock; the cells in the pineal body are activated by changes in daylight and darkness. This helps set the rhythm of activity and rest for the animal. Lizards, unlike snakes, the other members of Order Squamata, have movable eyelids and external ear openings. Also unlike snakes, the jaws of a lizard are fused, the bones at the hinge are connected, and thus restrict the size of the prey they can swallow.
When threatened by predators, lizards can shed their tail in 1 or more pieces and will slowly grow a new tail. Who eats lizards? Anybody who can catch them. This includes birds, mammals like raccoons or foxes, other lizards and snakes; we also have one documented case of a fence lizard being devoured by a large praying mantis. As a group, only 1% of lizards are herbivores, only eating plants. The other 99% will eat insects, mammals, birds, and other reptiles. When confronted by a threat, a predator or competitor for territory, lizards will displays a variety of behaviors designed to deter the threat. Common threat displays in lizards include color changes, body inflation, push-ups, jaw gaping, tail waving, and head movements. Females generally lay eggs beneath rocks or logs.
Snakes (Order Squamata, Suborder Serpentes)
2,389 species worldwide, 27 species in Maryland
Snakes have the dual distinction of being one of the most feared animals and one of the most revered in cultures throughout the world. The Greek caduceus, which to this day remains a symbol of doctors and healing, has two intertwining snakes. Snakes are vertebrates with backbones containing anywhere from 200 to 400 vertebrae. At one time snakes were thought to move by “walking” on their ribs, but what actually happens is that the snake remains still while the movement occurs from the ventral scutes.
All snakes eat animals including frogs, fish, eggs, snails, and insects. Some snakes eat other snakes. The jaw bones of a snake are not fused at the hinge between the top jaw and the bottom jaw. This makes the mouth opening very flexible, allowing the snake to eat large or oddly shaped prey. In winter or during the dry season, snakes den with other snakes. A female will disperse from the den with mature eggs in her oviduct; she will lay these eggs in rotting logs or sandy soil under rocks. Some species of snakes will birth live young; the eggshells essentially dissolving in the mother's body. The young hatch or are born live 3-4 months after mating.
Maryland's Venomous Snakes
Perhaps the most feared snakes are the venomous snakes, which represent evolutionarily advanced families. The venom kills the prey and begins the digestive process, but it can be used in self-defense if the snake feels cornered. Venom toxins come in four general varieties: neurotoxic, which interferes with the nerve impulses from the brain to the muscles; cytotoxic which can affect cell membranes of prey at the site of the bite; hemolytic which act on the heart and cardiac system, including blood; and proteolytic which affect the protein structure of the molecules of the area surrounding the bite. Rarely is a snake's venom made up of only one type of toxin. It is usually a mix but there will be a dominant type.
In Maryland, we have two venomous snakes, the Timber Rattlesnake (Crotalus horridus) and the Copperhead (Agkistrodon contortrix). They are both in the Pit Viper family (Crotalinae) and therefore their venoms are primarily of the cytotoxic and hemolytic varieties. A bite from a non-venomous snake should be taken seriously as well. Proteins in snake saliva could trigger a reaction in someone with an unknown sensitivity. The victim of any snake bite should immediately seek medical help. (Many people think that the cottonmouth or water moccasin exists in Maryland but this species does not naturally occur here. It is a more southern snake and does not cross the Potomac.)
In the case of an envenomed bite, damage is usually most severe around the site of the bite. Reactions will vary according to the victim's general health, the victim's sensitivity to the venom, the location of the bite, and the amount of venom injected, even the size and physical health of the snake. Immediate reactions at the bite site may include: pain, swelling, redness, bruising and bleeding. Over time, the victim may experience nausea or vomiting, increased swelling and redness beyond the bite site, lowered blood pressure, racing heart rate, muscle weakness and lethargy. In extreme cases in which the victim is not in optimal health or has other illnesses (especially in the elderly and in children), death is possible. Some symptoms may be caused by the venom and some may be caused by the victim's own natural fear response and understandable anxiety.
These are old methods which don't work and may cause a worse reaction and increase infection.
Even non-venomous snakes will bite if they are mis-handled or feel trapped. These bites should be taken seriously; although they don't contain venom, they are puncture wounds that may contain traces of snake saliva. Puncture wounds should be cleansed well with soap and water and watched closely. A tetanus shot might be required by your doctor.
It is important to remember that most snake bites in Maryland are avoidable. Both timber rattlesnakes and copperheads are relatively shy species, rarely aggressive. Most snake bites, both venomous and non-venomous, result from deliberate attempts to handle, harm, or kill the snake. Remember that snakes are wild animals and should not be approached or handled.
Photo of Northern Water Snake Eating a fish, courtesy of John White
- Discover Maryland's Herps
- Maryland Herp History
- Maryland Herp Checklist
- Survey Techniques, Collecting Ethics, Safety and the Law
- Problems with Buying Frogs and Tadpoles for Wild Release
- Technical Guide: A Key to the Reptiles and Amphibians of Maryland - 86.3 MB pdf file
- Maryland Amphibian and Reptile Atlas (MARA) Project
- Natural Heritage Program
- Wildlife & Heritage Home
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The Maryland Herpetology Field Guide is a cooperative effort of the MD Natural Heritage Program and the MD Biological Stream Survey within the Department of Natural Resources and their partners. We wish to thank all who contributed field records, text, and photographs, as well as support throughout its development.