Amphibians and Reptiles of the Rainforests of Southern El Petén, Guatemala

Part 1

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UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 15, No. 5, pp. 205-249, pls. 7-10, 6 figs.

-------------- October 4, 1963 --------------

Amphibians and Reptiles of the Rainforests of Southern El Peten, Guatemala

BY WILLIAM E. DUELLMAN

UNIVERSITY OF KANSAS LAWRENCE 1963

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Theodore H. Eaton, Jr.

Vol. 15, No. 5, pp. 205-249, pls. 7-10, 6 figs. Published October 4, 1963

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY JEAN M. NEIBARGER, STATE PRINTER TOPEKA, KANSAS 1963

29-5935

Amphibians and Reptiles of the Rainforests of Southern El Peten, Guatemala

WILLIAM E. DUELLMAN

CONTENTS

PAGE INTRODUCTION 207 Acknowledgments 208

DESCRIPTION OF AREA 208 Physiography 209 Climate 209 Vegetation 209

GAZETTEER 210

THE HERPETOFAUNA OF THE RAINFOREST 211 Composition of the Fauna 212 Ecology of the Herpetofauna 212 Relationships of the Fauna 217

ACCOUNTS OF SPECIES 218

HYPOTHETICAL LIST OF SPECIES 246

SUMMARY 247

LITERATURE CITED 247

INTRODUCTION

Early in 1960 an unusual opportunity arose to carry on biological field work in the midst of virgin rainforest in southern El Peten, Guatemala. At that time the Ohio Oil Company of Guatemala had an air strip and camp at Chinaja, from which place the company was constructing a road northward through the forest. In mid-February, 1960, J. Knox Jones, Jr. and I flew into El Peten to collect and study mammals, reptiles, and amphibians. While enjoying the comforts of the fine field camp at Chinaja, we worked in the surrounding forest and availed ourselves of the opportunity to be on hand when the road crews were cutting the tall trees in the forest, thereby bringing to the ground many interesting specimens of the arboreal fauna. We stayed at Chinaja until late March, with the exception of a week spent at Toocog, another camp of the Ohio Oil Company located 15 kilometers southeast of La Libertad and on the edge of the savanna. Thus, at Toocog we were able to work both in the forest and on the savanna. In the summer of 1960, John Wellman accompanied me to El Peten for two weeks in June and July. Most of our time was spent at Chinaja, but a few days were spent at Toocog and other localities in south-central El Peten.

Many areas in Guatemala have been studied intensively by L. C. Stuart, who has published on the herpetofauna of the forested area of northeastern El Peten (1958), the savannas of central El Peten (1935), and the humid mountainous region to the south of El Peten in Alta Verapaz (1948 and 1950). The area studied by me and my companions is covered with rainforest and lies to the north of the highlands of Alta Verapaz and to the south of the savannas of central El Peten. A few specimens of amphibians and reptiles were obtained in this area in 1935 by C. L. Hubbs and Henry van der Schalie; this collection, reported on by Stuart (1937), contained only one species, Cochranella fleischmanni, not present in our collection of 77 species and 617 specimens.

Part 2

Acknowledgments

I am grateful to L. C. Stuart of the University of Michigan, who made the initial arrangements for our work in El Peten, aided me in the identification of certain specimens, and helped in the preparation of this report. J. Knox Jones, Jr. and John Wellman were able field companions, who added greatly to the number of specimens in the collection. In Guatemala, Clark M. Shimeall and Harold Hoopman of the Ohio Oil Company of Guatemala made available to us the facilities of the company's camps at Chinaja and Toocog. Alberto Alcain and Luis Escaler welcomed us at Chinaja and gave us every possible assistance. Juan Monteras and Antonio Aldana made our stay at Toocog enjoyable and profitable. During our visits to southern El Peten, Julio Bolon C. worked for us as a collector, and between March and June he collected and saved many valuable specimens; his knowledge of the forest and its inhabitants was a great asset to our work. Jorge A. Ibarra, Director of the Museo Nacional de Historia Natural in Guatemala assisted us in obtaining necessary permits and extended other kindnesses. To all of these people I am indebted for the essential parts that they played in the completion of this study.

Field work in the winter of 1960 was made possible by funds from the American Heart Association for the purposes of collecting mammalian hearts. My field work in the summer of 1960 was supported by a grant from the Graduate Research Fund of the University of Kansas.

DESCRIPTION OF THE AREA

A vast lowland region stretches northward for approximately 700 kilometers from the highlands of Guatemala to the Gulf of Mexico. The northern two-thirds of this low plain is bordered on three sides by seas and forms the Yucatan Peninsula. The lowlands at the base of the Yucatan Peninsula make up the Departamento El Peten of Guatemala. The area with which this report is concerned consists of the south-central part of El Peten.

Physiography

Immediately south of Chinaja is a range of hills, the Serrania de Chinaja, having an almost due east-west axis and a crest of about 600 meters above sea level. South of the Serrania de Chinaja are succeedingly higher ridges building up to the Meseta de Coban and Sierra de Pocolha and eventually to the main Guatemalan highlands. The northern face of the Serrania de Chinaja is a fault scarp dropping abruptly from about 650 meters at the crest to about 140 meters at the base. From the base of the Serrania de Chinaja northward to the Rio de la Pasion at Sayaxche the terrain is gently rolling and has a total relief of about 50 meters. North of the Rio de la Pasion is a low dome reaching an elevation of 170 meters at La Libertad; see Stuart (1935:12) for further discussion of the physiography of central El Peten. The rocks in southern El Peten are predominately Miocene marine limestones; there are occasional pockets of Pliocene deposits. There is little evidence of subterranean solution at Chinaja, but northward in central El Peten karsting is common. The upper few inches of soil is humus rich in organic matter; below this is clay.

Climate

The climate of El Peten is tropical with equable temperatures throughout the year. Temperatures at Chinaja varied between a night-time low of 65 deg. F. and a daytime high of 91 deg. F. during the time of our visits. In the Koeppen system of classification the climate at Chinaja and Toocog is Af. Rain falls throughout the year, but there is a noticeable dry season. To anyone who has traveled from south to north in El Peten and the Yucatan Peninsula, it is obvious from the changes in vegetation that there is a decrease in rainfall from south to north. There is a noticeable difference between Chinaja and Toocog. Although rainfall data are not available for Chinaja and Toocog, there are records for nearby stations (Sapper, 1932). At Paso Caballos on the Rio San Pedro about 40 kilometers northwest of Toocog the average annual rainfall amounts to 1620 mm.; the driest month is March (21 mm.), and the wettest months are June (269 mm.) and September (265 mm.). At Cubilquitz, Alta Verapaz, about 35 kilometers south-southwest of Chinaja and at an elevation of 300 meters, the average annual rainfall is 4006 mm.; the driest month is March (128 mm.), and the wettest months are July (488 mm.) and October (634 mm.).

During the 18 days in February and March, 1960, that we kept records on the weather at Chinaja moderate to heavy showers occurred on seven days. During our stay there in June and July rain fell every day, as it did in Toocog. However, during the week spent at Toocog in March no rain fell.

Vegetation

The vegetation of northern and central El Peten has been studied by Lundell (1937), who made only passing remarks concerning the plants of the southern part of El Peten. No floristic studies have been made there. The following remarks are necessarily brief and are intended only to give the reader a general picture of the forest. I have included names of a few of the commoner trees that I recognized.

Chinaja is located in a vast expanse of unbroken rainforest. In this forest there is a noticeable stratification of the vegetation. Three strata are apparent; in the uppermost layer the tops of the trees are from 40 to 50 meters above the ground. The spreading crowns of the trees and the interlacing vines form a nearly continuous canopy over the lower layers. Among the common trees in the upper stratum are Calophyllum brasiliense, Castilla elastica, Cedrela mexicana, Ceiba pentandra, Didalium guianense, Ficus sp., Sideroxylon lundelli, Swietenia macrophylla, and Vitex sp. (Pl. 1, fig. 1). The middle layer of trees have crowns about 25 meters above the ground; these trees in some places where the upper canopy is missing form the tallest trees in the forest. This is especially true on steep hillsides. Common trees in the middle layer include Achras zapote, Bombax ellipticum, Cecropia mexicana, Orbignya cohune, and Sabal sp. The lowermost layer reaches a height of about 10 meters; in many places in the forest this layer is absent. Common trees in the lower stratum include Crysophila argentea, Cymbopetalum penduliflorum, Casearia sp., and Hasseltia dioica.

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