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Yosemite Nature Notes

THE MONTHLY PUBLICATION OF
THE YOSEMITE NATURALIST DEPARTMENT
AND THE YOSEMITE NATURAL HISTORY ASSOCIATION

REPTILES and AMPHIBIANS

of
YOSEMITE NATIONAL PARK

By Myrl V. Walker, Associate Park Naturalist

INTRODUCTION

Numerous books, bulletins and notes have been published on the Amphibians and Reptiles of North America, Western North America, and the Pacific Coast. No effort has been made in this publication to present new data, but rather to take the information already available and to apply it to a rather restricted geographic unit in the Sierra Nevada region of California.

The technical herpetologist may be disappointed when he finds that this bulletin has failed to indicate original authors and name changes by proper use of parentheses. He will also notice that a “middle of the road” course has been followed in the selection of specific and sub-specific names. No attempt has been made in this bulletin to justify or defend the specific names used, for such is not the primary purpose of this publication.

The goal of this bulletin is to provide for the greatest number of people a guide to the ready recognition of forms in a limited area, and furthermore, to emphasize the value of the recognition of forms and their inter-relationships as an influence in the maximum utilization of the interpretive recreational values preserved in such areas as our National Parks.

ACKNOWLEDGMENTS

To the University of California Press and the California Academy of Sciences special thanks are given for the loan of cuts, photographs, and other assistance. The writer appreciates the assistance, counsel and guidance of John R. Slevin, Joseph S. Dixon, Hector H. Lee, Robert C. Stebbins, Bertha Lutz, Leo F. Hadsall, William G. Hilton, C. P. Russell, C. Frank Brockman, and all others who either assisted in securing cuts or gave of their time to road and check the manuscript. To Park Photographer Ralph H. Anderson special credit is due for his patience and skill in securing certain photographs.

Interest in Reptiles and Amphibians

For the most part the average person’s interest in reptiles and amphibians is negative rather than positive. Many people are far more interested in the tall-tales commonly circulated about reptiles and amphibians than they are in their life habits, their relationships, or their economic value. Some people listen with interest to the stories of joint-snakes; snakes that swallow their young; hoop snakes, and milk snakes, but their interest soon lags when they delve into these mysteries and find them vanishing one by one— into thin air. Although we know that toads do not cause warts just because they are handled, there are some who still like to frighten the children with this old whip of parental control, which may if over-worked, develop into a phobia of considerable consequence. This latter fact is often a great deterrent to the proper understanding and appreciation of this division of vertebrate animals, and causes many to avoid even the casual study or observation of this interesting group.

Practically all young children show little or no fear of snakes, but rather a genuine interest. This attitude is certainly far different than the hysterical behaviour of those who have already developed a phobia because they have been frightened by older people.

All snakes are carnivorous in their habits and therefore belong to the group called “predators,” meaning that they prey upon other animal forms. This fact is of great importance in any study of snakes, for food supply is a limiting factor in their economic value, their abundance, and their distribution. Although some snakes are generally present in any given locality, their abundance or scarcity is limited largely by the three requirements: — temperature, food and cover.

A number of our snakes prey almost exclusively on amphibians, so in a study of this kind one soon realizes the control effect of snakes on toads, frogs and salamanders. Changing conditions, such as the draining of swamps or the disappearance of wet meadows which result in a sudden drop in toad, frog or salamander populations, will in turn soon act to lower the number of snakes of certain species.

The lizards are for the most part less “disturbing” to the average person than are the snakes, and since most of them have four legs and run, rather than crawl, they occupy a higher place in the scale of human tolerance. Few realize, however, their economic value for they feed largely on invertebrate forms, many almost exclusively on insects. Many lizards in turn serve as food for certain snakes.

The amphibians—toads, frogs and salamanders—occupy a better place in the scale of tolerance, although there are some people who do not hesitate to destroy even these harmless forms. Their economic value determined by this large number of invertebrates, especially insects, which they destroy. The amphibians are kept in control by the snakes and other animals which prey upon them.

The snakes are not without their natural enemies. Many snakes are destroyed by carnivorous mammals and by birds of prey. Some hawks are known to destroy many snakes each season. The most recent and perhaps the most devastating enemy of the snake is the automobile. Many snakes are killed by cars traveling at high speed on asphalt surfaced roads which retain heat at night and thereby attract the snakes, or perhaps the snakes are attracted by the large number of rodents — ground squirrels and mice—that have also fallen victim to this modern age of speed and motor car.

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