Reptiles
Author: Ray Bowers

Description:
Living reptiles have dry skin that is covered with scales, which are shed individually, partially, or as a whole unit. Some reptiles, such as the turtles and tortoises also have bony plates forming a shell. Reptiles are primarily exothermic, which means they depend on external sources of heat. Most reptiles have four legs, with the exception of a few lizards and all snakes. Reptiles have a three or four chambered heart which is efficient in delivering oxygen rich blood to the body. Adult reptiles can vary from 40mm (1.6in) to 9m (29.5ft ) in length, and can weigh up to 500Kg ( 1,100lbs ). Reptiles have a variety of sense organs. Some have color vision, while others see in shades of gray. The ability to hear varies within the reptiles, with some having well developed ears. The sense organs for smell are found in the nasal passages of turtles and crocodiles, but are found in the roof of the mouth of lizards and snakes, where the tongue aides in smelling. Some snakes, such as rattlesnakes, have infrared or heat sensors found in a pit on the front of the head, giving them the common name of pit vipers.

Geographic range:
There are around 6,000 living reptiles worldwide, and 97 in New Mexico . The oldest fossil identified as a reptile is about 321 million years old. Reptiles are found on all continents except Antarctica , where they are primarily found in temperate and tropical areas. Reptiles are found in all of New Mexico 's counties.

Habitat:
Reptiles are found in all temperate and tropical terrestrial and aquatic habitats. Most New Mexican habitats have reptiles present with the exception of the cold wind-swept environments of the highest elevations.

Food Web:
Most reptiles are carnivorous . Feeding on a variety of other animals, while some are omnivorous feeding on both plant and animal material. An evolutionary change that occurred was the development of glands in the mouth that allowed for the feeding on dryer foods. Some of these glands in the mouth have evolved into poison glands. Reptiles are in turn fed upon by a variety of larger animals, such as spiders, fish, frogs, other reptiles, birds, and mammals.

Reproduction and Development:
Reptiles usually lay leathery eggs, but in some cases reptiles are ovoviviparous, where the eggs are retained inside the female until they are ready to hatch. In most cases, reptile eggs are left to hatch on their own, but a few species brood the eggs or protect the nest. There is some evidence that some females may provide some protection for the newly hatched young.

Behavior:
Reptiles often have a period of inactivity during the year that is related to climatic conditions. Reptiles also use behavior to control their body temperature during the day, basking in the Sun to warm their bodies or seeking shade to cool the body. Some reptiles are active hunters, while others sit and wait for prey to pass. The carnivorous feeding behavior may explain the variety of courtship behaviors found in different species as a way of avoiding being considered a meal. Some reptiles as protection from predation use threat or warning behaviors, such as the vibrating of the tail of the rattlesnake. Feeding behavior usually involves swallowing the prey whole, and in snakes the jaw can be dislocated allowing the swallowing of prey larger than the head.

Ecosystem roles:
Reptiles play an important role as insect and rodent predators, and some farmers appreciate the role of snakes in rodent control.

Conservation:
Hunting and habitat destruction have caused some reptile populations to decrease. Hunting may be for the pet trade or due to the fear of snakes, especially the venomous species. This fear of snakes is not well founded because of the importance of snakes in rodent control. New Mexico has laws controlling the collection of reptiles for the pet trade. The expansion of urban areas into areas that were rural has also had a negative affect on reptile populations.

Cool Links:

• San Diego Natural History Musuem
  
• New Mexico Herpetological Resources

Taxonomy:

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptiles, Reptilia

Of the 4 orders of reptiles, 2 orders occur in New Mexico:

Order Chelonia: turtles
		Family Chelydridae: snapping turtles Family Emydidae: box turtles and water turtles Family Kinosteridae: mud turtles Family Trionychidae: softshelled turtles
Order Squamata: lizards and snakes
	Suborder Sauria: lizards
		Family Crotaphytidae: collard and lepard lizards Family Phrynosomatidae: zebratail, earless, spiny, tree, side-blotched, and horned lizards Family Gekkonidae: geckos Family Teiidae: whiptail lizards Family Scinicidae: skink lizards Family Anguidae: alligator lizards Family Helodermatidae: gila monster, a venomous lizard
	Suborder Serpentes: snakes
		Family Leptotyphlopidae: blind snakes Family Colubridae: rat, racer, ringneck, hognose, king, coachwhip, water, gopher or bull, patchnose, and garter snakes Family Elapidae: coral snakes Family Vivperidae: rattlesnakes, such as the blacktailed rattlesnake or the Western diamondbacked rattlesnake

References:
Degenhardt, William G. et al. 1996. Amphibians and Reptiles of New Mexico . Albuquerque : University of New Mexico Press

House Bill 282

Milius, Susan. 2004. "The Social Lives of Snakes." Science News . Vol. 165, No 13, pp200-201.

Orr, Robert T. 1976. Vertebrate Biology . Philadelphia : W.B. Saunders.

Young, J. Z. 1981. The Life of Vertebrates . Oxford , England : Clarendon Press.

Related Terms: Chordata