Morelet's Crocodile (Crocodylus moreletii) in the Macal River watershed, Maya Mountains, Belize PETER J. STAFFORD', SCOTT T. McMURRY2, THOMAS R. RAINWATER2, DAVID A. RAYS, LLEWELLYN D. DENSMORE3, and BRADY BARR4 I The Natural History Museum, Cromwell Road, London SW7 SBD, UK [author for correspondence] 2 The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX 79416, USA 3 Department of Biological Sciences, Texas Tech University, Lubbock, TX 79416, USA 4 National Geographic Society, Washington DC, USA ABSTRACT — Results are presented of an investigation into the status of Morelet's Crocodile in the Macal River watershed, a little known upland tributary system in Belize. During spotlight surveys in February 2001 and September 2002, numerous individuals were observed representing a wide range of size classes. Sequence analyses of mtDNA from captured animals show that crocodiles in the area represent a genetically pure strain of C. moreletii. No evidence of hybridisation with the American Crocodile (C. acutus) was detected, as observed in animals from other sampled localities (northern lowlands). Due to their relative isolation, crocodiles in the Macal watershed may thus function as a regionally important population source for C. moreletii should introgression with C. acutus spread over time. Differences between C. moreletii in the Macal and northern lowlands were apparent also in aspects of ecology. 1VI ORELET'S Crocodile (Crocodylus moreletii) is one of two species of crocodilian found in Belize (Lee, 1996; Stafford & Meyer, 2000). It occurs primarily in freshwater habitats, especially in the northern part of the country, a flat limestone shelf dominated by extensive lagoons, alluvial swamps, and flooded sinkholes. The remaining species, C. acutus, is restricted to offshore islands and coastal areas of the mainland (Platt & Thorbjamarson, 2000a). Commercial harvesting for its high quality leather had depleted populations of C. moreletii throughout its entire range, and by the late 1960s the species is believed to have been nearly exterminated in Belize (Neill, 1971; Frost, 1974). Following legal protection afforded in 1981, however, its numbers have since recovered significantly. Surveys undertaken recently of C. moreletii in Belize have focused mostly on the northern lowlands (e.g. Abercrombie et al., 1980, 1982; Platt, 1996; Rainwater et al., 1998; Platt & Thorbjarnarson, 2000a), where at some localities the species appears to be common. At Gold Button Lagoon in the Orange Walk District, Platt (1996) counted 159 individuals representing an encounter rate of 22.08 crocodiles per km of the shoreline. More recent observations have confirmed the presence of C. moreletii at various localities in southern Belize east of the central mountain divide (Platt et al., 1999). Crocodiles are also known to inhabit some of the larger rivers and streams that drain the western slopes of this little known mountain range (Maya Mountains), particularly the Macal and its larger tributary, the Raspaculo Branch, but with only a small number of records available the occurrence and distribution of populations in the area remain inadequately assessed. In this paper we review the status of C. moreletii in the Macal watershed based on recent surveys and other data collected periodically over the last ten years. Much of this system is threatened with flooding should plans to construct a hydro-electric storage dam at Chalillo, a locality on the Macal some 12 km downstream from its Number 85 - Herpetological Bulletin [2003] 15