Mr. Bouyer
Day 1 | Day 2 | Begin Lab Project | Reading Assignment

Recognize the difference between poisonous and non-poisonous snakes in Texas. Group snake venoms based on their effects on the victim's body. Use a dichotomous key to identify Texas snake Families.

Animal Identification Assignment.

The bite of which poisonous snake is commonly treated only with aspirin?

Snakes are in the Order Squamata, Suborder Ophidia.

All snakes are predatory and swallow their prey whole.

Texas' poisonous snakes:

The most common poisonous snake across the state is the western (southern) copperhead, Agkistrodon contortrix, pictured at right. The eastern (northern) copperhead is also found in the state.

All poisonous snakes in Texas are pit vipers. The name comes from an opening between the eye and nose that leads to a heat-sensing organ. These snakes do not have good eyesight. They locate prey by following scent and then picking up its body heat.

The notorious cotton mouth water moccasin, Agkistrodon piscivorous, is found in several areas of the state. It inhabits warm, swampy areas. The cotton mouth gets its name for the white color of the inside of its mouth. There are several things to notice about the snake in this picture. The algae giving it the green color is an indication of the very warm and moist habitat of the snake. The picture is that of a mature adult. Notice that it is not very long (about 3 feet), but its diameter is quite large. Notice that the tail is short, tapering quickly from the body. Young cotton mouths have a mottled coloration similar to a copperhead, but the adults are almost uniform brown to black.

Many people will see a snake swimming in the water and call it a water moccasin. But most of these sightings are of the common water snake, Natrix sipedon. The Natrix in this picture is longer than the cotton mouth in the earlier picture, but its diameter is obviously less. Notice that the tail is long, tapering slowly from the body. The Natrix is aggressive, especially when threatened. Although it is not poisonous and has no fangs, it does have several rows of sharp teeth and WILL bite.

Texas is home to several types of rattlesnakes, two of which are quite small. The smallest is the pigmy rattlesnake, Sistrurus miliarus, which is less than two feet long. The massasauga, Sistrurus catenatus, might reach three feet in length.

The largest rattlesnake is the western diamondback, Crotalus atrox. Individuals are commonly reported that are over six feet in length. Although its color ranges from brown to tan to gray, it is easily identified by a tail with distinct broad black rings separated by white, causing some people to refer to it as the "coon-tailed" rattlesnake.

The other widely distributed rattlesnake in Texas is the timber rattlesnake, Crotalus horridus. The tail of this rattlesnake is dark, almost black, causing some people to refer to it as the "velvet-tailed" rattlesnake.

Types of snake venom:

All snake venoms contain substances destructive to tissue cells, nervous tissue and blood cells, in addition to other components which cause a wide variety of symptoms. The amount of each of these substances varies from species to species. Here are the four major chemical groups in venoms:

• Thrombase - causes local thrombosis, the coagulation of blood in the blood vessels at the site of the bite.
• Anticoagulin - thins the blood.
• Hemorrhagin - causes lysis (breaking down) of cells in the capillaries causing hemorrhaging in skin and mucous membranes. If hemorrhagin reaches the capillaries of the brain, the small hemorrhages can cause convulsions.
• Neurotoxin - produces a paralytic effect on the respiratory center and the cranial nerves.

Two types of kingsnakes are common in our area. The prairie kingsnake, Lampropeltis calligaster, is often mistaken for a copperhead because of its coloration. You can clearly see in this picture that the head of the kingsnake does not have the characteristic triangle shape of the copperhead. The coloration of the speckled kingsnake, Lampropeltis holbrooki, is unlike any other, making it easy to identify. Kingsnakes will kill and eat other snakes, which should cause people who don't like snakes to appreciate them.

One of the largest snakes in our area is the bullsnake, Pituophis melanoleucus. The color of the bullsnake ranges from the tan in this picture to almost yellow.

In-Class Assignment 141:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria

1. How do you distinguish between an eastern copperhead and a western copperhead?
2. Which copperhead are you most likely to find in our area?
3. How is a western diamondback rattlesnake recognized?
4. What type of venom is produced by poisonous snakes in Texas?
5. Judging from their symptoms, is hemotoxic venom or neurotoxic venom more immediately life-threatening?
6. What is the first thing you should do if bitten by a poisonous snake?
7. What are the two extreme measures that are very rarely needed to treat a snake bite?
8. What nonpoisonous snake in our area might be mistaken for a copperhead?

Day 2

The coral snake is more dominant in the coastal area. We do have nonpoisonous snakes with coloration similar to that of the coral snake. How do the colorations of these Texas snakes differ from the coral snake?

Snake identification:

The pattern of scale arrangement and the configuration of scales provide the most useful basis for identification. Your first step in learning to use dichotomous keys for snake identification is to become acquainted with the typical scalation.

Scales keeled or smooth:

Snake scales may be "keeled" with a ridge down the middle. These ridges make the snake feel rough when handled.

Snake scales may be "smooth". The lack of ridges on the scales maks the snake feel smooth when handled.

Anal scale divided or undivided:

The cloacal opening is covered with a scale, the "anal", which may be single or divided into 2 parts.

Portfolio Assignment 142:
Scoring criteria

1. The scale known as a "loreal" is located between the "nasals" and what other scales?
2. When three scale counts are given on a key, where are the counts made on the snake?
3. Use the information about families of snakes to answer the following questions:
   1. What is the family name for pit vipers?
   2. What is the common name for Heterodon platyrhinos?
   3. What is meant by an arboreal snake?
   4. Which family contains 75% of the species of snakes in the U.S.?
   5. What are scales on the belly of a snake called?
   6. Coral snakes do not have regular fangs. How do they deliver their venom?
   7. Is the anal plate of the speckled kingsnake divided?

Research Links:

• Howe Reptile Checklist - Howe High School
• Class Reptilia - University of Washington
• Snakes of North America - University of Pittsburgh
• Chordate Anatomy and Evolution - George Washington University
• How to Identify Snakes - South Carolina Reptiles and Amphibians
• Scale Counts - Sean Thomas
• A Field Guide to the Reptiles and Amphibians - USGS Western Ecological Research Center

Zoology Class

The bite of a copperhead is commonly treated only with aspirin.
Copperheads have the mildest venom of any poisonous snake in Texas. The chemicals used to neutralize the bite are almost as hard on the body as the snake's venom.

The color bands on coral snakes run all the way around the body. The color bands of the nonpoisonous snakes stop at the belly scales.

coral snake   ||   scarlet kingsnake   ||   milk snake

"Red on black is friend of Jack. Red on yellow will kill a fellow."