Natural history of the terciopelo Bothrops asper (Serpentes: Viperidae) in Costa Rica Mahmood Sasa a, * , Dennis K. Wasko b , William W. Lamar c a Instituto Clodomiro Picado, Universidad de Costa Rica, San Jose´, Costa Rica b Department of Biology, University of Miami, Coral Gables, FL 33124 USA c Department of Biology, The University of Texas at Tyler, TX 75799, USA article info Article history: Received 25 February 2009 Received in revised form 17 June 2009 Accepted 18 June 2009 Available online 27 June 2009 Keywords: Lancehead pitviper Viperidae Bothrops Home range Ontogenic dietary change La Selva abstract The terciopelo Bothrops asper is the only lancehead species widely distributed in the humid lowlands of Middle America and northwestern South America. Its large body size, relative abundance and cryptic habits contribute to the high incidence of snakebites induced by this species throughout its distribution. The terciopelo plays an important role in ecosystems, both as prey and as a generalist predator. Diet comprises a great variety of prey items, including some species that are considered nuisances. B. asper, as other lan- cehead species, exhibits a notable ontogenetic shift in diet, consuming ectotherms (mainly frogs and lizards) when young, and increasingly incorporating birds, rodents, and other small mammals with maturity. Adult terciopelos also consume large anurans, especially when endothermic prey availability is low. Using radiotelemetry we determined home range and movement patterns from 28 indi- vidual B. asper at La Selva Biological Station, Costa Rica. Overall home range estimates are relatively small compared with other pitvipers, averaging between 3.71 ha and 5.95 ha; home range size did not differ between males and females. Movement patterns are largely aseasonal and consist of short (<10 m) movements between daytime shelter and nocturnal ambush sites within a given area, interspersed with longer distance (>50 m) movements to new foraging areas. Habitat use is related to prey availability and therefore to foraging strategy. Our data support a strong preference for areas near swamps by both sexes. Reproduction in B. asper is highly seasonal, and – apparently – biannual. Reproductive cycles in Costa Rica are tightly related to rainfall patterns. Therefore, the timing of breeding differs between populations in the Caribbean and Pacific lowlands. Bothrops asper is adapted to areas with low levels of disturbance along the agricultural frontier, and consequently it is not rare to find it in or near human dwellings. However, despite popular belief, no evidence supports a purported increase in population density of this species in Costa Rica. Despite human persecution and substantial modification of habitat, B. asper is a species with a conservation status of least concern, and probably will likely persist well into the future. Thus, it is important to learn how to coexist with this species, and to improve mechanisms for the prevention and treatment of accidental snakebite and its consequences. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The genus Bothrops comprises over 37 species commonly referred to as lanceheads (Campbell and Lamar, 1989, 2004) which are chiefly distributed in South America, * Corresponding author. Tel.: þ1 506 2229 3135; fax: þ1 506 2292 0485. E-mail address: msasamarin@gmail.com (M. Sasa). Contents lists available at ScienceDirect Toxicon journal homepage: www.elsevier.com/locate/toxicon 0041-0101/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.toxicon.2009.06.024 Toxicon 54 (2009) 904–922