New Mexico's Reptiles and Amphibians

A Field Guide

R. D. Bartlett, Patricia P. Bartlett

• Publisher: UNM Press
• Year: 2013
• Print ISBN: 9780826352071
• eBook ISBN: 9780826352088
• Topic: Ciencias biológicas
• Subtopic: Zoología

New Mexico is home to 165 species and subspecies of snakes, lizards, turtles, frogs, toads, and salamanders. Some are ubiquitous and others are localized. If you want basic and reliable information on the lizard in your backyard or the snake you encountered on a hike in the mountains, this handy field guide is invaluable. Both complete and concise, it includes species accounts, maps, photographs, and black-and-white drawings to help you identify the species you have encountered. In addition to basic taxonomy and a glossary, the authors have included suggestions on field protocol and legalities, as well as useful information about the various herpetofauna habitats in the state.

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ABOUT AMPHIBIANS AND REPTILES

AMPHIBIANS

Today, the class Amphibia, a grouping of creatures that came into existence some 350 million years ago during the Devonian period, contains about 5,500 species that are divided into three divergent groups: the frogs (including toads and treefrogs), the salamanders, and the caecilians. Only the first two groups occur in New Mexico, the frogs and the salamanders, and there are just 27 species.

Though of diverse appearance, amphibians have many characteristics in common. They have moist skins; lack hair, feathers, or scales; they lack true claws; and by definition (but sometimes not in actuality) amphibians lead a “double life,” most spending their larval state in the water and their adult life on land.

As they metamorphose from larva to adult, amphibians undergo dramatic body reorganization. They resorb their external gills, most develop lungs and eyelids, and all New Mexican species grow legs. Their skin cells adapt to largely nonaqueous environment. During metamorphosis their mouths are reshaped, their intestine shortens, and other internal changes occur.

But the “double life” is not always apparent. New Mexico is a state with little standing water, and our amphibian species reflect this. Two of the salamander species in New Mexico skip the water-dependent larval stage.

Allow us to define a few words that you will see many times in the text:

Anuran = a tailless amphibian; a frog, toad, or treefrog.

Caudatan = a tailed amphibian; a salamander.

The term frog is less cut and dry, for in actuality toads and treefrogs are often referred to as frogs but the term is not suitable when so used. An analogy would be that all robins are birds, but not all birds are robins.

The larvae of all frogs, toads, and treefrogs are called tadpoles or pollywogs; those of the salamanders are referred to simply as larvae, or in the case of the larger ambystomatids, as waterdogs.

Tadpoles have internal gills (external when first hatched), modified scraping mouthparts, and lack eyelids. Larval salamanders have external gills.

Most tadpoles are herbivorous and have a very long intestine to enable them to process and digest vegetable matter. Larval salamanders consume animal matter.

As tadpoles begin metamorphosis the tail is resorbed, providing energy for the creature as its gut shortens and changes from a vegetarian to a carnivorous diet. Often many tadpoles metamorphose simultaneously, and there are times when hundreds of tiny toadlets or froglets may be found hopping around the edge of a breeding pond. Newly metamorphosed frogs are difficult to identify for at metamorphosis they have few if any identifying features. However, within days identifying characteristics become observable.

Salamanders of many species lay their eggs in water and the larvae are aquatic, but some species lay their eggs on land. Some of the species that lay their eggs on land place their eggs near the water so the hatching larvae can drop into water. But the larvae of two New Mexican species larvae undergo direct development within the egg capsule and emerge as tiny replicas of the adults. The larvae of aquatic salamanders may lack functional legs at hatching (many pond-dwelling species) or their legs may be fully functional (stream dwellers).

Larval aquatic salamanders have three pairs of external gills until they metamorphose. At metamorphosis most, but not all salamanders have functional lungs. However, the salamanders of the family Plethodontidae are lungless, relying on their moist skin and mucous membranes for oxygen absorption.

Interestingly, amphibian larvae are able to regenerate lost or broken appendages such as limbs, tail, gill stalks, and gill filaments. Some jaw and eye damages are also known to have been regenerated. Metamorphosed adults are not capable of regeneration.

The amphibians of New Mexico are of diverse appearance and size, but all are relatively small. For example, when adult, a frog may be 1 inch in length (cricket frogs) or 8 inches long (bullfrog). Salamanders vary from a slender 3½ inches (Jemez Mountains and Sacramento Mountains salamanders) to the 10-inch length of the tiger salamanders.

Amphibian populations are adversely affected by many pressures. Among these are habitat modifications; death on roadways as the creatures try to access breeding ponds or new habitats; collection for the pet trade; the use of herbicides, insecticides, and other pollutants in the environment; and what seems to be the newest documented pathogen, chytrid fungi. Droughts and floods can also take a toll. Because of the breeding site fidelity of some species, habitat fragmentation and the filling of breeding ponds can be particularly devastating. All said, many native amphibians are having a tough go of things and many populations are thought to be diminishing precipitously.

REPTILES

Reptiles evolved from reptiliomorph amphibians about 315 million years ago. The oldest known fossils of true reptiles are the footprints of Hylonomus, an 8–12-inch-long, lizard-like reptile.

A few years ago it would have been relatively simple to estimate the number of reptiles alive in the world today, for at that time there were four orders within the class Reptilia: the turtles and tortoises; the snakes, lizards, and amphisbaenians; the crocodiles and alligators; and the tuataras.

Today there are nomenclatural changes, both proposed and actual. Systematists suggest that neither the turtles nor the crocodilians are actually reptiles and that a new class should be erected for each. Additionally, it is presently believed that the birds are more closely allied to the reptiles than the crocodilians are. And it is now generally accepted as fact that snakes are merely modified lizards and are somewhere near the skinks (possibly between the skinks and the iguanids) in the overall scheme of reptilian ancestries.

But now with all of this having been said, let’s estimate that the “reptiles” number somewhere in the vicinity of 7,500 species. Of this number only about 109 species (turtles included) occur in New Mexico.

The reptiles—the turtles, lizards, and snakes—are ectothermic, “cold-blooded” if you will. To attain and retain a body temperature that will allow them to be active, they must thermoregulate. At its simplest, this may require basking periodically in the sun to elevate core temperature or conversely seeking shadows to prevent a further rise in body temperature or to actually decrease temperatures. Taking this a step or two further, some species may regulate their optimal body temperatures by changing activity patterns with the seasons, being diurnal early and late in the year when temperatures are moderate and crepuscular during the heat of summer.

In New Mexico there are reptile species to fill almost every ecological niche. Some are secretive woodland dwellers (alligator lizards), desert species (the collared lizards, leopard lizards, and whipsnakes), or inhabitants of montane heights (ridge-nosed rattlesnake and greater short-horned lizard).

Of the turtles and tortoises, mud turtles may secrete themselves in seeps so small that it would seem the turtles would have difficulty staying wet, while the desert tortoise roams the dry flats and arroyos in search of nourishing vegetation. You will meet all in these pages.

How do you go about finding reptiles in New Mexico? The finding of many species can be described in three words—luck, knowledge, and dedication!

Some species (rattlesnakes, long-nosed snakes, and banded geckos among them) may be rather easily found basking on or crossing sun-warmed roadways from shortly after dusk has fallen to the wee hours of the morning. When the early morning sun begins to again warm the roadway and desert you may see racers, rat snakes, collared lizards, or spiny lizards basking on rocks and dirt clods at road edge or on the pavement itself. If you walk rock-edged desert trails you may also see collared lizards and whiptails far into the desert.

Because reptiles are of great interest, many species are often kept as captives. Be aware that both state and federal laws may regulate the capture and/or keeping of some species. Familiarize yourself with the laws, and be aware that if a reptile is collected in violation of a state law and then taken across a state line, the violation becomes a federal offense.

HABITATS IN NEW MEXICO

You will see the term habitat referred to in every species account as well as elsewhere in this book. As used here, habitat simply refers to the area in which a creature preferentially lives. A habitat for a specific amphibian or reptile must provide food, shelter, and access to water/moisture. As you search, you’ll soon recognize habitat types that provide the necessities for the various types of amphibians and reptiles.

The term climate encompasses temperature range and humidity/rainfall. Temperature varies dramatically by season and altitude and the amount of sunlight that reaches the earth must also be factored in. Knowing the needs of a particular species will help you in your search for it. For example, Blanchard’s cricket frog (Acris blanchardi), a very small frog, is dependent on fresh water for all stages of its life cycle. Look for it in wetland and river-edge habitats in the drainage of the Pecos River in the southeastern corner of the state. Conversely, you would search for the banded rock rattlesnake (Crotalus lepidus klauberi) in rocky montane canyons and on or around escarpments.

Higher elevations mean cooler temperatures, with about a 3°F drop for each thousand foot increase. Santa Fe at 7,000 feet is always 4–6°F cooler than Albuquerque at 5,100 feet. Temperatures are dependent on latitude but to a lesser extent than altitude. Similar elevations in the north and south differ in mean temperatures of only 3°F. These higher elevations have relatively thinner air and heat up faster and cool down more quickly at night. Montane reptiles and amphibians begin moving a bit earlier in the morning and have a shorter activity window in the evening. If you’re headed for the mountains, you’ll find only those species with small body mass, such as the fence lizards, Sceloporus spp., active in the early morning.

Moisture, or the lack of it, is a very real limiting factor not only in what can live in the state but where in the state the animal can be found. Some reptiles can meet their moisture needs with their diet or by licking dew off their own bodies or from leaves and rocks. Most amphibians need standing water for part of their life cycle, and as a result comparatively few species occur in xeric New Mexico.

With few rivers, airborne moisture is an important source of water. Mountain ranges dominate the western two-thirds of the state, and not too surprisingly, the mountains determine where the water goes. The Continental Divide meanders north–south over the westernmost quarter of the state. The Gila, Zuni, and San Juan Rivers eventually drain into the Gulf of California. Rivers on the eastern side of the Continental Divide, notably the Rio Grande, the Canadian, and Pecos, drain into the Gulf of Mexico. (If you like isolation and can carry a lot of water, you may find it of interest that the Continental Divide Trail Society maintains a trail that follows the divide in New Mexico.) Moisture-laden winds from Pacific weather systems moving eastward lose more moisture with each mountain chain with which they collide, leaving rain shadows on the eastern lowlands and valleys. The southeasterly winds from the Gulf of Mexico bring moisture into the eastern part of the state. Those winds cool as they hit the Sangre de Christo and Sacramento mountain ranges and then drop their moisture on the eastern New Mexican plains.

All in all, not a lot of moisture reaches the central portion of the state. Annual rainfall along the western side of New Mexico averages 14 inches while Albuquerque gets just a bit over 8 inches. What rain the inland area gets tends to come from summer thunderstorms, which form quickly, drop their moisture, and vanish. The runoff creates washouts (arroyos) which are norma...

Table of contents

• Cover
• Half title
• Title
• Copyright
• Contents
• Species List
• 1. About Amphibians and Reptiles
• 2. Frogs, Toads, and Treefrogs
• 3. Salamanders
• 4. Turtles
• 5. Snakes
• 6. Lizards
• Acknowledgments
• Glossary
• References and Additional Reading
• Index