BULLETIN of the Chicago Herpetological Society Volume 54, Number 7 July 2019 BULLETIN OF THE CHICAGO HERPETOLOGICAL SOCIETY Volume 54, Number 7 July 2019 Notes on the Herpetofauna of Northwestern Mexico 2: Tortuga Island, Gulf of California, Mexico . Gustavo Arnaud, David Lazcano and Larry David Wilson 137 Head Triangulation in Dipsas turgida (Cope, 1868) (Dipsadidae, Dipsadinae, Dipsadini): A Potential Deimatic Behavior? . Paul Smith 142 Notes on Reproduction of Great Basin Spadefoot Toads, Spea intermontana (Anura: Scaphiopodidae) . Stephen R. Goldberg 145 Movin’ On Up! Some Notes on Arboreal Behaviors with Three Species of Fossorial Snakes: Sonoran Coralsnakes (Micruroides euryxanthus), Western Threadsnakes (Rena humilis) and Spotted Nightsnakes (Hypsiglena chlorophaea) . Roger A. Repp 148 What You Missed at the June Meeting: Show & Tell . .John Archer 153 Herpetology 2019......................................................... 155 Advertisements . 156 New CHS Members This Month . 156 Cover: Tortuga Island in the Gulf of California, Mexico. Google Earth image © 2018 DigitalGlobe STAFF Membership in the CHS includes a subscription to the monthly Bulletin. Annual dues are: Individual Membership, $25.00; Editor: Michael A. Dloogatch --- [email protected] Family Membership, $28.00; Sustaining Membership, $50.00; Copy editor: Joan Moore Contributing Membership, $100.00; Institutional Membership, Photo editor: Steve Barten $38.00. Remittance must be made in U.S. funds. Subscribers outside the U.S. must add $12.00 for postage. Send membership 2019 CHS Board of Directors dues or address changes to: Chicago Herpetological Society, Membership Secretary, 2430 N. Cannon Drive, Chicago, IL 60614. President: Rich Crowley Vice-president: Jessica Wadleigh Manuscripts published in the Bulletin of the Chicago Herpeto- Treasurer: John Archer logical Society are not peer reviewed. Manuscripts and letters Recording Secretary: Gail Oomens concerning editorial business should be e-mailed to the editor, Media Secretary: Kim Klisiak [email protected]. Alternatively, they may be mailed Membership Secretary: Mike Dloogatch to: Chicago Herpetological Society, Publications Secretary, 2430 Sergeant-at-arms: Mike Scott N. Cannon Drive, Chicago, IL 60614. Back issues are limited but Members-at-large: Dan Bavirsha are available from the Publications Secretary for $2.50 per issue Tom Mikosz postpaid. Cindy Steinle Sammy Velazquez Visit the CHS home page at <http://www.chicagoherp.org>. The Bulletin of the Chicago Herpetological Society (ISSN The Chicago Herpetological Society 0009-3564) is published monthly by the Chicago Herpeto- is a nonprofit organiza- logical Society, 2430 N. Cannon Drive, Chicago IL 60614. tion incorporated under the laws of the state of Illinois. Its Periodicals postage paid at Chicago IL. Postmaster: Send purposes are education, conservation and the advancement address changes to: Chicago Herpetological Society, Mem- bership Secretary, 2430 N. Cannon Drive, Chicago IL 60614. of herpetology. Meetings are announced in this publication, and are normally held at 7:30 P.M., the last Wednesday of each month. Copyright © 2019 Bulletin of the Chicago Herpetological Society 54(7):137-142, 2019 Notes on the Herpetofauna of Northwestern Mexico 2: Tortuga Island, Gulf of California, Mexico Gustavo Arnaud 1, David Lazcano 2 and Larry David Wilson 3 Introduction Thirty-one taxa of lizards (56.4%) and 14 taxa of snakes (38.9%) are endemic to one or several islands (Blázquez et al., 2018). The Gulf of California islands belong to the Reserve and The species of the genus Crotalus are an important ecological Refuge Areas for Migratory Birds and Wildlife and are sites of element of the endemic fauna of these islands; they all play an reproduction, nesting, resting, and feeding for marine wildlife important role as primary predators (Ruiz-Sanchez et al., 2019). and migratory birds (Tershy and Croll, 1994). In spite of this status, the population sizes, distribution, abundance, and natural The Gulf of California islands are a priority for conservation history of most of the reptiles living on these islands are unknown. of biodiversity in Mexico (Vázquez-Domínguez et al., 1998). Therefore, we need to understand the natural biodiversity and The conditions of the islands are variable, because they are resources they support. Most of the islands are not inhabited by not homogeneous in origin, age, geology, or distance from the people; they are visited, however, by tourists, fishermen and coast (Case et al., 2002). The islands of the Gulf of California scientists. The resulting impact on the terrestrial ecosystems has are classified into three types: oceanic, continental, and land- not yet been evaluated (López-Espinosa de los Monteros, 2002). bridge (Grismer, 2002). The oceanic islands have never been In this context, we have documented herpetological information connected to Baja California peninsula or mainland Mexico. for the little-known Tortuga Island (Isla Tortuga). The continental islands were once connected to the Baja Califor- nia peninsula and/or mainland Mexico, but became separated as Our Goals a result of tectonic displacements along coastal fault zones, and broke off the trailing edge of the peninsula as it moved north- Lack of information about the ecology and abundance of the west. The landbridge islands are the commonest and youngest of Mexican insular herpetofauna makes it important to increase our all the islands in the Gulf of California, and were connected to knowledge of this group of vertebrates. We hope that through Baja California or mainland Mexico, but for the most part, were ecological and educational programs on mainland Baja Califor- cut off by a rise in sea level (Grismer, 2002). nia, we can foster greater awareness of the importance of this group of organisms and promote further protection and conser- The climate of the islands is very arid, with summer rains vation of the islands. and little or no winter precipitation. The vegetation is dense in glens and along streams, contrasting with the rocky, arid slopes. Study Area Such places are a refuge for reptiles. These islands have a highly diverse terrestrial herpetofauna of 92 species, distributed on 68 Tortuga Island is an oceanic island, located at 27E26'00" N islands, including one tortoise, 55 lizards, and 36 snakes. The and 111E52'00" W in the Gulf of California (Figure 1), and has percentage of endemicity is 48%, one of the highest in the world. an area of 11.36 km² (dimensions approximately 4.7 × 3.3 km). Figure 1. Location and physiography of Tortuga Island in the Gulf of California, Mexico. Source: Google Earth 1. Centro de Investigaciones Biológicas del Noroeste, La Paz, Baja California Sur, CP 23096, México. ([email protected]) 2. Laboratorio de Herpetología, Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Apartado Postal 157, San Nicolás de los Garza, Nuevo León, C.P. 66450 México. ([email protected]) 3. Centro Zamorano de Biodiversidad, Escuela Agrícola Panamericana Zamorano, Departamento de Francisco Morazán, Honduras; 16010 SW 207th Ave, Miami, FL 33187-1056, USA. ([email protected]) 137 small ravines where the dominant species are Stenocereus gum- mosus (sour pitaya), Bursera spp. (elephant tree), Lophocereus schottii (senita cactus), and Lycium brevipes (Baja desert thorn). On the high plains, the dominant species are Stenocereus gum- C) E mosus, Fouquiera diguetii (desert coral), Atriplex barclayana (dwarf saltbush), Pachycereus pringlei (Mexican giant cactus), Bursera spp., Colubrina viridis (snakewood), and Lycium brevipes. Temperature ( Temperature Precipitation (mm) Mammals The only mammal on the island is Peromyscus dickeyi (Dickey’s mouse). This mouse is found in all habitats of the Figure 2. Annual climogram of the Tortuga Island region. The line island, except at the bottom of the cone and is the primary food graph shows average daily temperature using the scale on the left. The item for the rattlesnake species (Crotalus tortugensis = C. atrox). bar graph plots average monthly precipitation using the scale on the right. Birds The island is a volcanic cone with an elevation of 309 m The bird community of the island is composed of seven (Murphy et al., 2002). The physiography is dominated by volca- resident terrestrial species, among which are Zonotrichia nic rocks. The island lacks beaches and its shoreline consists leucophrys (white-crowned sparrow), Pipilo chlorus (green- primarily of cliffs, which make it inaccessible. The island is tailed towhee), Amphispiza bilineata (black-throated sparrow), covered by irregularly shaped volcanic rocks, within and under and Corvus corax (Raven). The wintering species are Dendroica which reptiles take refuge. Tortuga is located 36.3 km from the nigrescens (black-throated gray warbler) and Vermivora city of Santa Rosalía in the municipality of Mulegé, Baja Cali- ruficapilla (Nashville warbler) (Cody and Velarde, 2002). fornia Sur on the Baja California Peninsula, México. The human population of Santa Rosalía is 14,000. Tortuga island is unin- Methods habited by humans; fishermen do not establish fishing camps Eight sampling visits were conducted during the course of because they are afraid of rattlesnakes, which they say are plen- five years (April, September 2009; April 2010; June, August tiful. Tourists too do not visit the island because of the snakes. 2011; July 2012; and October 2014). Sampling time was 2 or 3 nights and 2 to 3 days on each occasion. Reptiles were