Status of Siamese Crocodile (Crocodylus siamensis) Schneider, 1801 (Reptilia: Crocodylia) in Laos
The Siamese Crocodile (Crocodylus siamensis) is critically endangered and, until a decade ago, few remaining wild populations were known to exist. Described here are the first in-depth surveys for C. siamensisin Laos with new field data on ecology and conservation. Small breeding populations of C. siamensisare confirmed to persist in Laos. During surveys between 2003 and 2008, C. siamensiswas recorded in 13 sites of six river systems, where at least 36 individuals (1–11 per site) were documented. In all sites, crocodile densities and recruitment rates were extremely low. Eight nests were recorded—among the first wild nests of C. siamensisto be reported. Perennial, thickly vegetated floodplain lakes are critical dry-season refugia and breeding habitats for C. siamensisin Laos. Opportunistic collection of crocodiles by local communities was observed, and at all sites there is increasing degradation of floodplain lakes for agriculture or economic development. National crocodile records were compiled and indicate that, historically, C. siamensiswas widespread in lowland riverine and palustrine habitats of Laos, with most records from Central and South Laos in the Mekong Plain. These records also suggest that a severe range decline has occurred over the past century, although most wetlands remain unsurveyed for crocodiles. Crocodylus siamensisis probably now extirpated from the Lao Mekong and many other wetlands. Remnant C. siamensispopulations in Laos are of global importance. All documented breeding sites, and most confirmed national records, are in rural lands outside the national protected area system, and conservation efforts will require community-based approaches.Abstract
Survey sites and other localities mentioned in the text. Solid triangles are sites where crocodiles are reported from the literature. PFA = Provincial Forestry Area. Provinces where sites were surveyed between 2003 and 2008 are shaded in grey on the inset map of Laos.
Crocodile records for Laos 1867–2008.
a–f. Habitats of Crocodylus siamensis in Laos. Few published photographs are available of C. siamensis habitat from its global range. Perennial floodplain lakes: (a) Bung Pulon, partly cleared–burned (deep-water areas are in center of photo); (b) Kout Mak Peo, undisturbed wetland vegetation on thick floating mat (the most-intact site visited and which supported the highest number of crocodile signs, see text); (c) Xe Lat Gnai, partly cleared, extensive infestation of floating weed Eichhornia crassipes (foreground). Perennial rivers: (d) Xe Champhon (adjacent to site in 2b), extensive sand bars; (e) Xe Don, slow-flowing, mud banks; (f) Xe Lanong, swift-flowing, rocky substrate. Photos by Mark R. Bezuijen, Wildlife Conservation Society (WCS). Used with permission.
Wild Crocodylus siamensis, among the first photographs from Laos of this species. (a) Adult female, Bung Boua Thong, February 2003 (ZRC [IMG] 2.131). Photo by John B. Thorbjarnarson, WCS. Used with permission. (b) Adult female at nest, Bung Ho, October 2008 (ZRC [IMG] 2.132a] (reported to be the same individual as in Fig. 3a). Photo by Jack H. Cox, WCS. Used with permission. (c) Hatchling, Kout Mak Peo, April 2005 (ZRC [IMG] 2.135a). Photo by Mark R. Bezuijen, WCS. Used with permission. (d) Captive juvenile, Kout Kaen, May 2008 (ZRC [IMG] 2.139b). Photo by Jack H. Cox, WCS. Used with permission.
. Crocodylus siamensis nest, Kout Kouang Gnai, May 2008, Laos (ZRC [IMG] 2.145a]. (a) Nest mound. (b) Cavity with eggs. Photo by Jack H. Cox, WCS. Used with permission.
Historical distribution of Crocodylus siamensis in Laos overlaid with current (≥1980) records.
Contributor Notes
Deceased
