Revista de Biología Tropical ISSN: 0034-7744 ISSN: 2215-2075 Universidad de Costa Rica Solórzano, Alejandro; Sasa, Mahmood Redescription of the snake Lachesis melanocephala (Squamata: Viperidae): Designation of a neotype, natural history, and conservation status Revista de Biología Tropical, vol. 68, no. 4, 2020, October-, pp. 1387-1400 Universidad de Costa Rica DOI: https://doi.org/10.15517/RBT.V68I4.42359 Available in: https://www.redalyc.org/articulo.oa?id=44966323031 How to cite Complete issue Scientific Information System Redalyc More information about this article Network of Scientific Journals from Latin America and the Caribbean, Spain and Journal's webpage in redalyc.org Portugal Project academic non-profit, developed under the open access initiative ISSN Printed: 0034-7744 ISSN digital: 2215-2075 Redescription of the snake Lachesis melanocephala (Squamata: Viperidae): Designation of a neotype, natural history, and conservation status Alejandro Solórzano1* & Mahmood Sasa2 1. Museo de Zoología, Universidad de Costa Rica, Ciudad Universitaria Rodrigo Facio, San Pedro de Montes de Oca, San José, Costa Rica; [email protected] 2. Instituto Clodomiro Picado y Escuela de Biología, Universidad de Costa Rica, Ciudad Universitaria Rodrigo Facio, San Pedro de Montes de Oca, San José, Costa Rica; [email protected] * Correspondance Received 18-VI-2020. Corrected 18-VIII-2020. Accepted 11-IX-2020. ABSTRACT. Introduction: The Black-headed Bushmaster (Lachesis melanocephala) is a large venomous snake that inhabits tropical moist forest, wet forest, montane and premontane wet forest in Southwestern Costa Rica and extreme Western Panama. Objective: We assign a neotype for the species due to the loss of the original holotype and update the information on its geographical distribution, natural history, and conservation status. Methods: To determine the conservation status of L. melanocephala, we modeled its potential distribu- tion using the species` locality records and distribution modeling analysis implemented in MaxEnt. Based on the species’ potential distribution, we evaluate the loss of its original habitat and estimate the percentage of its distribution area that is currently protected by the country’s protected area system. Results: The potential distribution of the species was estimated at 10 139 km2, including areas where the species currently occurs and historical areas where the species has been registered but is nowadays considered locally extinct. About 29 % of that potential distribution overlaps with protected wild areas, so less than a third of the potential distribution of the species is under protection. Conclusions: During the last decade, accelerated habitat loss and growing evidence of declining natural populations indicate the need for urgent protective measures to prevent the extinc- tion of this species in the foreseeable future. Key words: Neotropical pitvipers; snake conservation; species distribution model. Solórzano, A., & Sasa, M. (2020). Redescription of the snake Lachesis melanocephala (Squamata: Viperidae): Designation of a neotype, natural history, and conservation status. Revista de Biología Tropical, 68(4), 1384-1400. The genus Lachesis (n.f., Daudin, 1803) allow distinguishing them. In its distal part, represents a clade of Neotropical pitvipers that the caudal region has small, bristling scales, includes four nominal species distributed in even in the sub-tail area (Fernandes, 2001). the rainforest of South America and Isthmian The tail ends on a spine-shaped scale; some Central America (Campbell & Lamar, 2004; authors suggest it is involved in producing a Wallach, Williams, & Boundy, 2014). These warning sound when vibrates against the leaf are the longest venomous snakes in the West- litter (Ripa, 1994). The dorsal scales are warty, ern Hemisphere and are considered the longest almost pyramidal, giving it a rough and warty vipers in the world (Campbell & Lamar, 2004). appearance (the vernacular name assigned to Besides their large size, species within Lache- bushmasters in Panamá and Colombia refers to sis share several external characteristics that that appearance). The dorsal coloration consists 1384 Rev. Biol. Trop. (Int. J. Trop. Biol.) • Vol. 68(4): 1384-1400, December 2020 of a background of light brown, cream, or clay (Solórzano & Cerdas, 1986). The dorsal ground tones depending on the species and has a pat- color is light, cream-white to yellowish, with tern of dark rhomboid designs that extends from rhomboidal markings that are dark gray or the dorsal spine to the sides. These designs also black (Fig. 1D). Lachesis melanocephala has vary interspecifically. The bushmaster species the most restricted distribution, occurring in also share a unique feature among Neotropical Southern and Southwestern Costa Rica (Sav- pitvipers: they are oviparous, conceivably the age, 2002; Solórzano, 2004; Sasa, Chaves, & only members of Viperidae that lay eggs in Porras, 2010). This species also occurs near the New World (Campbell & Lamar, 2004; see the border with Costa Rica in Western Panama, this same reference for a possible exception in in the Province of Chiriquí (Dwyer & Perez, Bothrocophias colombianus). 2009, see below). Among the bushmaster species, the Black- Populations currently assigned to L. mela- headed Bushmaster (Lachesis melanocepha- nocephala were first considered a synonymy la) is considered the most distinctive: the back of Lachesis muta (Daudin, 1803). In Costa of its head is heavily pigmented, forming a Rica, early researchers did not distinguish unique black cap (Fig. 1A, Fig. 1B, Fig. 1C). between bushmaster populations at each side This characteristic makes this species locally of the Cordillera Volcánica Central and the known as Plato Negro (black plate), and the Talamanca mountain range, but they were epithet “melanocephala” refers precisely to aware of their presence (Picado, 1931; Taylor, that dark coloration on the back of the head 1954). Later, Vial & Jiménez-Pórras (1966) Fig. 1. Neotype of Lachesis melanocephala MZUCR-23185. A. Lateral view of head. B. Dorsal view of the head. C. Chin region. D. Full view. Note the dorsal body blotches. Rev. Biol. Trop. (Int. J. Trop. Biol.) • Vol. 68(4): 1384-1400, December 2020 1385 and Bolaños (1982) distinguished the Pacific propose the species status for L. melanoceph- and Caribbean forms, although they did not ala and Lachesis stenophrys. Subsequently, offer a formal taxonomic proposal. During Fernandes (2001) and Fernandes, Franco, & those years, differences in venom character- Fernández (2004) confirm the Central Ameri- istics between the Caribbean populations (= can forms as valid species, separated from L. Lachesis stenophrys) and the South Pacific muta, from morphological characters related population were recognized by Roger Bolaños to squamation, hemipenes morphology, and and collaborators at Instituto Clodomiro Picado coloration patterns. (ICP), Universidad de Costa Rica (Bolaños, The ICP museum collection was neglected Muñoz, & Cerdas, 1978). during 1996-2000, resulting in the loss of Solórzano & Cerdas (1986) first described many specimens during that period. One of Lachesis melanocephala as a subspecies of the most painful losses was the holotype and Lachesis muta. Besides their venom immuno- paratypes of Lachesis melanocephala. These logical differences, the authors found morpho- losses forced the cessation of maintaining the logical evidence to support that Caribbean and scientific collection at the Institute and the Pacific bushmaster populations were distinct decision to send the remaining specimens to forms that warrant different taxonomic status. the Museum of Zoology, at the Universidad de In the original description, the type series was Costa Rica (MZUCR). collected from 1984 to 1986 in the Southern Probably due to its relatively recent region of Puntarenas Province, Costa Rica. All description and coupled with the fact that it specimens were deposited in the Museo Insti- is an uncommon species, the biology, and tuto Clodomiro Picado (MICP), a snake collec- conservation status of L. melanocephala has tion established in 1984 by one of us (ASL) at not received much attention by the scientific ICP in San José. The holotype MICP-301 was mainstream (Solórzano, 2004). In fact, much an adult male (1969 mm snout-vent length), of the information available on the ecology and collected 9 km Northern of Ciudad Neily. The behavior of this species comes from observa- paratypes localities were: MICP-302: Palmar tions in captivity (see the section on Natural Norte; MICP-303: Corcovado National Park history, below). on Península de Osa; MICP-304: Golfito; In recent years, interest in this species MICP-305: Palmar Sur; MICP-306: Sabalito de has grown. Using ecological niche modeling, Coto Brus; MICP-307: Alturas del Río Cotón, González-Maya, Castañeda, González, Pache- East from Valle de Coto Brus (Solórzano & co, & Ceballos (2014) estimated the extent of Cerdas, 1986). occupation for L. melanocephala in less than It would take another decade before the 10 500 km2. According to these authors, the Black-headed Bushmaster was recognized as restricted distribution and high specificity to a full species. Ripa (1994) first suggested undisturbed habitats impose risky conditions the convenience of elevating both L. mela- for the survival of this species, suggesting nocephala and L. stenophrys as valid species that this situation coincides with the IUCN but did not take action on his proposal. Zamu- criteria for categorizing