The Amphibians and Reptiles of Michoacan, Mexico Part 1

The Amphibians and Reptiles of Michoacan,Mexico.

by William E. Duellman.

INTRODUCTION

For almost 30 years North American herpetologists have been making extensive collections of reptiles and amphibians in Mexico. Some parts of the country, because of their accessibility, soon became relatively well known; other regions lying off the beaten path were bypa.s.sed or inadequately sampled. Princ.i.p.ally in the last decade herpetologists have been entering regions from which no collections previously were available in an attempt to fill gaps in known distributions and to discover unknown species of animals. In 1950 Dr. Donald D. Brand led an exploration party from the University of Texas to the poorly explored and faunistically unknown region of southwestern Michoacan. James A.

Peters accompanied Brand and collected amphibians and reptiles. In 1951 I welcomed the opportunity to accompany Brand on a second expedition to southwestern Michoacan. Such was the beginning of my interest in the herpetofauna of the region. I have been fortunate to return to Michoacan on four successive trips, all of which had as their purpose the acc.u.mulation of data on the herpetofauna that would result in a survey of the component species and an a.n.a.lysis of their distribution.

My original intention was to amplify Peters' (1954) study based on the collections made by him in 1950 and by me in 1951 in the Sierra de Coalcoman. But it soon became evident that in order to understand the relationships of the herpetofauna of the Sierra de Coalcoman, the species inhabiting the Tepalcatepec Valley and adjacent mountain ranges would have to be studied. In the course of making that study I examined all specimens from Michoacan already in museums.

There have been few detailed herpetofaunal studies in Mexico. The first such study of any consequence was that by Bogert and Oliver (1945) on the herpetofauna of Sonora. In that paper the authors a.n.a.lyzed the fauna from a geographic view and showed the transition from tropical species in the southern part of the state to members of the Sonoran Desert a.s.semblage to the north. Martin (1958) made a detailed study of the herpetofauna of the Gomez Farias region in southern Tamaulipas; he emphasized the ecological distribution of amphibians and reptiles in that region with special reference to cloud forests. Duellman (1958c) presented a preliminary geographic a.n.a.lysis of the herpetofauna of Colima with special reference to the continuity of the species inhabiting the lowlands. Zweifel (1960) discussed in detail the herpetofauna of the Tres Marias Islands and commented on the derivation of the fauna. Duellman (1960d) provided a detailed account of the geographic distribution of the amphibians known to occur in the lowlands of the Isthmus of Tehuantepec and attempted to account for the present patterns of distribution.

The present report is the first of two parts dealing with the herpetofauna of Michoacan. The purpose of this part is to present a full account of the species of amphibians and reptiles known to inhabit the state of Michoacan; the accounts of the species are accompanied by a brief description of the natural landscape and of the various a.s.semblages of species comprising the major faunistic groups within the region. A gazetteer of collecting localities is appended. The second part of the study, now in preparation, deals with the ecological and historical geography of the herpetofauna. Since the present part will be of interest primarily to systematic herpetologists, I have decided to separate it from the more general material of interest to biogeographers.

One of the major problems that faces the worker undertaking a faunal study is the presence of species or genera of unsettled systematic status. My work in Michoacan has been no exception; fifteen separate studies were undertaken in an attempt to solve systematic problems in certain groups. Some systematic problems still remain but are of little consequence insofar as the entire faunal picture is concerned, or are so involved as to be impractical to undertake at this time. In accounts of species, such problems are mentioned in the hope that they will interest some worker who will be inclined to investigate them.

ACKNOWLEDGMENTS

While engaged in the study of the herpetofauna of Michoacan I have built up a debt of grat.i.tude to many individuals, without whose aid my ambition to complete my study never would have been realized. I am especially grateful to those individuals who accompanied me in the field; Lee D. Beatty, Richard E. Etheridge, Carter R. Gilbert, Fred G.

Thompson, Jerome Tulecke, and John Wellman offered stimulating companionship and valuable a.s.sistance. On many occasions they suffered hardships on behalf of my interests.

Studies of my own specimens have been augmented by material from other inst.i.tutions. For permitting me to examine specimens in their care I am indebted to W. Frank Blair, Charles M. Bogert, Doris M. Cochran, William B. Davis, James R. Dixon, the late Emmett R. Dunn, Josef Eiselt, Alice G. C. Grandison, Norman Hartweg, Robert F. Inger, Arthur Loveridge, the late Karl P. Schmidt, Hobart M. Smith, Robert C. Stebbins, Margaret Storey, Edward H. Taylor, and Richard G. Zweifel.

Several people have aided me in the study of specimens and in the a.n.a.lysis of data; I am grateful to Donald D. Brand, who first introduced me to Michoacan; since that time I have benefited much from his knowledge of the area. James A. Peters provided me with essential information concerning his field work in southern Michoacan in 1950.

James R. Dixon and Floyd L. Downs have permitted me to use freely the material and data that they acc.u.mulated in their recent field work in Michoacan. Norman E. Hartweg allowed me to use the specimens and data that he gathered in his survey of the herpetofauna in the region of Volcan Paricutin. L. C. Stuart, Charles F. Walker, and Richard G.

Zweifel have helped in unraveling some of the systematic and distributional problems.

I am especially grateful to my wife, Ann, who for six months helped me track down elusive species and explore new areas. Furthermore, she has stimulated me to carry this study to completion.

Many people in Michoacan favored the field parties with quarters, transportation, and valuable information, which greatly facilitated the field work. In this respect I am especially indebted to Ingeniero Ruben Erbina of Ingenieros Civiles Asociados, who not only let us use his home as our headquarters, but through a letter of introduction gave us the "key" to southern Michoacan. Ingeniero Pedro Tonda aided us in Arteaga and San Salvador. Ingeniero Anastacio Perez Alfaro of the Comision Tepalcatepec in Uruapan provided the latest maps of southern Michoacan and much essential information pertaining to travel conditions in the area. Senor Nefty Mendoza gave us a home in Dos Aguas; this kindness allowed us to work in this interesting region during the height of the rainy season. Mr. and Mrs. Bob Thomas let us make use of their facilities at Hacienda Zirimicuaro. The naval officers at the Estacion Marina at Playa Azul made pleasant what might have been a dreadful stay in that small coastal village. To the managers and pilots of Lineas Aereas Picho in Uruapan I owe special thanks for going out of their way on more than one occasion to transport a stranded snake-hunter.

Throughout the months of field work beginning in 1955 I constantly have been aided by the authorities and workers of the Comision Tepalcatepec, a subdivision of the Secretaria de Caminos y Obras Publicas, and of the private corporation, Ingenieros Civiles Asociados. Much of the field work in Michoacan was made possible only through the co-operation of the natives who supplied mules, acted as guides, and aided in the collection of specimens. I have learned a great deal from these people. They will never see this report. Their work as guides, muleteers, and collectors greatly a.s.sisted me with the mountains of equipment that had to be piled on the backs of scrawny mules for transportation to places where the natives seldom trod. Their efforts in behalf of Don Guillermo never will be forgotten; I extend an especially hearty _muchas gracias_ to Benjamin, Ignacio, Jesus, Lorenzo, Mariano, and Remigio.

Much of the work on this report was done while I was a.s.sociated with the Museum of Zoology at the University of Michigan. I thank Norman E.

Hartweg and T. H. Hubbell for making available to me the facilities of the museum and for their numerous courtesies that aided me so much.

My field work in Michoacan was supported by the Museum of Zoology at the University of Michigan (1951), by the Horace H. Rackham School of Graduate Studies of the University of Michigan (1955), by the Penrose Fund of the American Philosophical Society (1956), by the Bache Fund of the National Academy of Sciences (1958), and by the University of Kansas Endowment a.s.sociation (1960).

Permits for collecting specimens in Mexico were provided by the Direccion General de Caza through the courtesy of Ing. Juan Lozano Franco and Luis Macias Arellano.

Historical Account

Unlike many parts of southern Mexico and northern Central America, Michoacan received no attention from the collecting expeditions of the European museums in the last century. The earliest known herpetological specimens from Michoacan were obtained by Louis John Xantus, who was appointed U. S. Consul to Colima in 1859. In April, 1863, Xantus collected at Volcan Jorullo in Michoacan; in April and May of the same year he collected along the coast of Michoacan between the Rio Cachan and the Rio Nexpa. His small collection of 19 extant specimens is in the United States National Museum. Alfredo Duges, a resident of Guanajuato, Mexico, made early contributions to the knowledge of the herpetofauna of Michoacan. In 1885 he described _Sonora michoacanensis_, and in 1891 he described _Eumeces altamirani_; from what is known of the distribution of these species, he probably had collected in the Tepalcatepec Valley.

During their biological survey of Mexico, Edward W. Nelson and Edward A.

Goldman spent a limited amount of time in Michoacan in 1892 and again in 1903 and 1904. Most of their collecting was done on the plateau in the north-central part of the state; their collections are in the United States National Museum. While collecting fishes in southern Mexico, Seth E. Meek obtained some amphibians and reptiles from Lago de Patzcuaro in 1904; these are in the collections of the Chicago Natural History Museum. In 1908 Hans Gadow ventured into the then unexplored "tierra caliente" of the Balsas Valley and collected at Volcan Jorullo and other localities in the valley. Later in the same year he collected at Guayabo, San Salvador, and Arteaga in the Sierra de Coalcoman and at Buena Vista and Cofradia in the Tepalcatepec Valley. His collections were deposited in the British Museum (Natural History) and the Naturhistorisches Museum Wien.

The first thirty years of the present century saw little more field work in Michoacan. In the 1930's Edward H. Taylor and Hobart M. Smith collected throughout much of Mexico. At various times they worked in Michoacan, princ.i.p.ally along the road from Mexico City to Guadalajara.

In 1935 Hobart M. Smith spent a week at Hacienda El Sabino south of Uruapan; he revisited the locality again in 1936 and made a large and important collection of amphibians and reptiles from the upper limits of the arid tropical scrub forest in the Tepalcatepec Valley. Specimens collected by Smith and Taylor were incorporated into the Edward H.

Taylor-Hobart M. Smith collection, which subsequently was deposited in part in the Museum of Natural History at the University of Illinois and in part in the Chicago Natural History Museum. In 1939 Hobart M. Smith collected at Patzcuaro and between Uruapan and Apatzingan; these collections, made while he was a Walter Rathbone Bacon Scholar of the Smithsonian Inst.i.tution, are deposited in the United States National Museum. In 1940 and 1941 Frederick A. Shannon, who was a member of the Hoogstraal Expeditions under the auspices of the Chicago Natural History Museum, collected on Cerro de Tancitaro and at Apatzingan; an account of the specimens collected there was published by Schmidt and Shannon (1947).

The eruption of Volcan Paricutin in February, 1943, attracted the attention of many biologists, a group of which from the Museum of Zoology at the University of Michigan collected in the Cordillera Volcanica in 1945 and 1947. The amphibians and reptiles were collected and studied by Norman E. Hartweg. In 1950 James A. Peters accompanied Donald D. Brand on a preliminary exploration of the western part of the Sierra de Coalcoman and adjacent Pacific coast of Michoacan; in the same year Peters collected also on the Mexican Plateau and at Volcan Jorullo.

His specimens are in the Museum of Zoology at the University of Michigan. Since 1950 many biologists have collected in Michoacan in the course of work on certain groups of animals or in general surveys. In this way Raymond Alcorn, Robert W. d.i.c.kerman, James R. Dixon, Floyd L.

Downs, Emmet T. Hooper, and Robert R. Miller have contributed to our knowledge of the herpetofauna.

As stated previously, my own field work in Michoacan began in 1951, when I accompanied Donald D. Brand on an exploring expedition to the southern part of the state. In that year a short time was spent on the Mexican Plateau, princ.i.p.ally in the area around Lago de Cuitzeo, and at Volcan Jorullo. In July and August we made our headquarters at Coalcoman. From that town the field party travelled southward to Maruata on the Pacific coast and thence back over the mountains to Coalcoman.

Later in that summer we travelled by mule from Coalcoman southeastward to the mouth of the Rio Nexpa. In 1955, accompanied by Lee D. Beatty, Carter R. Gilbert, and Fred G. Thompson, I collected in the Tepalcatepec Valley and at Coalcoman. We made a mule trip from Coalcoman to Cerro de Barolosa, where we made the first collections from the pine-fir forests in the Sierra de Coalcoman. Later in the same summer Carter R. Gilbert and I spent a week at Playa Azul on the Pacific coast. In March, April, and May, 1956, my wife and I collected for a short time in the Cordillera Volcanica and on the Mexican Plateau. In early April we moved into the Tepalcatepec Valley, where we collected intensively between Churumuco and Tepalcatepec. In May we collected on the Pacific coast between Boca de Apiza and La Placita. In July and August, 1956, accompanied by Richard E. Etheridge, we returned to Michoacan and again collected on the Mexican Plateau and in the Cordillera Volcanica, before moving into the Tepalcatepec Valley. In an attempt to fill in gaps in the known distributions of many species and to sample the fauna in some previously uncollected areas, I returned to Michoacan in June, 1958.

Accompanied by Jerome B. Tulecke and John Wellman, I collected on the Mexican Plateau in the northwestern part of the state, on the southern slopes of the Cordillera Volcanica, and in the Tepalcatepec Valley. Most of our time was spent in the Sierra de Coalcoman, where we collected at Aguililla, Artega, and Dos Aguas. In 1960 two days were spent in Michoacan; a small collection was made in the eastern part of the Cordillera Volcanica. With the exception of the specimens collected in 1960, which are at the Museum of Natural History at the University of Kansas, the specimens that I have collected in Michoacan are in the Museum of Zoology at the University of Michigan.

NATURAL LANDSCAPE

A proper understanding of the geographical distribution of animals in a given region is possible only after a thorough acquaintance with the geography of the region. Likewise, in order to gain a knowledge of the ecological distribution and relationships of the components of the fauna, it is necessary to study the animals in their natural environments. In order to give the reader a picture of the physical features and the major animal habitats within the state of Michoacan, the following brief description is offered. Each of these facets mentioned below will be elaborated in detail in my final report on the herpetofauna of Michoacan.

Physiography

The state of Michoacan comprises an area of 60,093 square kilometers (Vivo, 1953). Within this area the rugged terrain has a total relief of nearly 4000 meters. There have been several attempts to cla.s.sify the physiographic provinces of Mexico; the cla.s.sification used here is a slight modification of the scheme proposed by Tamayo (1949). I have tried to keep the system as simple as possible, but still useful in discussing the distribution of animals living in the region. For general purposes the state of Michoacan can be divided into lowlands and highlands as follows:

LOWLANDS Pacific Coastal Plain Balsas-Tepalcatepec Basin

HIGHLANDS Mexican Plateau Cordillera Volcanica Sierra de Coalcoman

Although the lowlands in the state are continuous, they are only narrowly connected and thus form two distinct physiographic and biotic areas. The Pacific Coastal Plain in Michoacan extends for a distance of about 200 kilometers (airline) from the Rio Coahuayana to the Rio Balsas. The coastal plain is broad between the Rio Coahuayana and San Juan de Lima, and between Las Penas and the Rio Balsas, where the hills rise some 12 kilometers inland from the sea. Between San Juan de Lima and Las Penas the mountains extend to the sea; in this region rocky promontories form precipitous cliffs dropping into the sea. Between the promontories are small sandy or rocky beaches.

Lying to the north of the Sierra de Coalcoman and the Sierra del Sur, but south of the Cordillera Volcanica, is a broad structural depression, the Balsas-Tepalcatepec Basin. The western part of this basin, which separates the Sierra de Coalcoman from the Cordillera Volcanica, is the valley of the Rio Tepalcatepec, a major tributary of the Rio Balsas. The eastern part of the basin is the valley of the Rio Balsas. From the point of junction of the two rivers, the Rio Balsas flows southward through a narrow gorge, which separates the Sierra de Coalcoman from the Sierra del Sur, to the Pacific Ocean. In Michoacan the floor of the Balsas-Tepalcatepec Basin varies from 200 to 700 meters above sea level.

The central part of Mexico is a vast table-land, the Mexican Plateau, the southern part of which extends into northern Michoacan. In this region the terrain is rolling and varies from 1500 to 1900 meters above sea level. Many small mountain ranges rise from the plateau and break the continuity of the rolling table-land. Located on the southern part of the Mexican Plateau in Michoacan are several lakes, the largest of which are Lago de Chapala, Lago de Cuitzeo, and Lago de Patzcuaro.

Bordering the southern edge of the Mexican Plateau is a nearly unbroken chain of volcanos, the Cordillera Volcanica. The highest peaks in Michoacan, Cerro San Andres (3930 meters) and Cerro de Tancitaro (3870 meters), are in this range. Parts of the Cordillera Volcanica in Michoacan are known by separate names; these are, from west to east: Sierra de los Tarascos, Sierra de Ozumatlan, and Serrania de Ucareo.

Lying between the Tepalcatepec Valley and the Pacific Ocean, and east of the Rio Coahuayana and west of the Rio Balsas, is an isolated highland ma.s.s, the Sierra de Coalcoman. This mountain range rises to elevations of slightly more than 3000 meters. It has a length of about 200 kilometers and a width of about 80 kilometers. Except for a relatively low connection with the Cordillera Volcanica, the Sierra de Coalcoman is isolated from other mountain ranges in southwestern Mexico.

CLIMATE

The climates in Michoacan vary from tropical in the lowlands to cool temperate at high elevations in the Sierra de Coalcoman and Cordillera Volcanica. The highest temperatures are known in the Balsas-Tepalcatepec Basin, where at Churumuco the mean annual temperature is 29.3 C. and the range of monthly means is 3.5 C. (Contreras, 1942). Frosts occur sporadically on the Mexican Plateau, and in the winter snow falls on the highest mountains.

Precipitation varies geographically and seasonally. Most of the rain falls between June and October. In the Balsas-Tepalcatepec Basin rainfall in the rest of the year is negligible. The annual average rainfall at Coahuayana on the Pacific Coastal Plain is 871 mm.

(Guzman-Rivas, 1957:52). In the Balsas-Tepalcatepec Basin rainfall seldom exceeds 800 mm. per year. In the mountains precipitation is heavier and somewhat more evenly distributed throughout the year, but still definitely cyclic. For example, Uruapan (elevation, 1500 meters) receives an average annual rainfall of 1674 mm. (Contreras, 1942). The prevailing winds are from the Pacific Ocean. The southern (windward) slopes of the Sierra de Coalcoman probably receive more rain than any other part of the state. The Balsas-Tepalcatepec Basin lies in a rain shadow of the Sierra de Coalcoman, and the Mexican Plateau lies in a somewhat less drastic rain shadow of the Cordillera Volcanica; these are the driest regions in the state.

VEGETATION AND ANIMAL HABITATS