Chilabothrus argentum 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Boidae

Scientific Name: Chilabothrus argentum Reynolds, Puente-Rolón, Geneva, Aviles-Rodriguez & Herrmann, 2016
Common Name(s):
English Conception Bank Silver Boa, Silver Boa
Spanish La Boa Plata
Taxonomic Source(s): Reynolds, R.G., Puente-Rolón, A.R., Geneva, A.J., Aviles-Rodriguez, K.J. and Herrmann, N.C. 2016. Discovery of a remarkable new Boa from the Conception Island Bank, Bahamas. Breviora 549(1): 1-19.
Taxonomic Notes: Chilabothrus argentum is a recently discovered species (Reynolds et al. 2016), unknown until July 2015. Species description was based on genetic and morphological analysis of six specimens, in the context of other Bahamian and West Indian boas. This species is divergent from other West Indian boas at an mtDNA locus and is readily distinguishable based on morphometric and morphological characteristics.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(i,ii,iii,v)+2ab(i,ii,iii,v) ver 3.1
Year Published: 2017
Date Assessed: 2017-08-04
Assessor(s): Reynolds, R.G.
Reviewer(s): Auliya, M. & Waller, T.
Chilabothrus argentum is a newly discovered species with a known distribution on a single island bank. Repeated surveys reveal that the species exists in a single isolated population, with an extent of occurrence of less than 7 km2 and an area of occupancy of 4 km2 (actually <1 km2 based on the area of the remaining habitat). It is likely that fewer than 1,000 individuals of all age classes exist, based on three mark-recapture sessions conducted on the population. Acute threats include small available habitat size, small population size, habitat damage owing to hurricanes and erosion, and the potential for human exploitation which are all causing a continuing decline. Chilabothrus argentum is therefore assessed as Critically Endangered based on criteria B1ab(i,ii,iii,v)+2ab(i,ii,ii,vi); making  the species one of the most threatened boid species globally.

Geographic Range [top]

Range Description:This species is currently known from a single island (<7 km2) on the Conception Island Bank. It seems likely, based on biogeographic analysis (Reynolds et al. 2016), that the species might previously have been more widespread on the Conception Island Bank, as well as possibly on the Rum Cay Bank (22 km southeast). Recent surveys of these other areas indicate that extant populations no longer exist (Reynolds et al. 2016).
Countries occurrence:
Additional data:
Estimated area of occupancy (AOO) - km2:4Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:7
Number of Locations:1
Lower elevation limit (metres):1
Upper elevation limit (metres):30
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is abundant in a very small forested area (<1 km2), and likely absent elsewhere on the island bank based on repeated surveys (R.G. Reynolds unpubl. data). Ongoing mark-recapture studies (R.G. Reynolds unpubl. data) suggest that fewer than 1,000 individuals exist in total.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:999
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This species is largely arboreal, occurring in relatively mature coastal forest dominated by Bursera simaruba trees and Cocothrinax argentata palms. Appears to require relatively mature forest, where it hunts migratory songbirds (Reynolds et al. 2016). The species might also feed on nesting native birds, including seabirds and waterbirds (R.G. Reynolds unpubl. data). Juveniles and young adults likely feed on the abundant Anolis sagrei on the island. The species is a nocturnal arboreal forager. Likely requires treeholes, large branches, rotten logs, rocks, and solution holes as refugia, particularly when hurricanes strike the island.
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):5

Use and Trade [top]

Use and Trade: As of July 2017 there is no known trade, as this species was unknown until July 2015. However, significant concern exists that the species will be exploited for the pet trade in the near future. The removal of even a small number of mature animals could doom the species to extinction. Other members of the genus have been heavily exploited for the pet trade, leading to the near-extirpation of at least one island population (Dodd 1986).

Threats [top]

Major Threat(s): The main threats are (1) likely historical range contraction, (2) potential exploitation, and (3) natural disaster:
  1. This species was likely more widespread in the recent past, being now restricted to a single island. This is likely owing to anthropogenic habitat modification, particularly on the islands of Rum Cay (potential historical range) and Conception Island. The latter has a history of use for agriculture (sisal plantations, possible burning and cutting of forest) early in the 20th century. 
  2. The recent discovery of this attractive species might lead to exploitation for the pet trade, as has happened with other members of the genus (e.g. Dodd 1986).
  3. The limited range of this species is threatened by habitat loss owing to hurricanes, as well as the potential for complete destruction of present habitat owing to rising sea levels. Hurricane Joaquin (October 2015) struck the island directly, causing an approximately 50 m x 10 m x 5 m section of beach/forest interface to erode into the sea. The island has a maximum height of 27 m asl, with much of the forest habitat occurring near present sea level. Thus, natural catastrophes, which might be exacerbated in intensity or frequency owing to climate change, should be considered a significant threat to the persistence of this species. Concomitantly, given the maximum elevation of the island, and the lower elevation of the remaining closed-canopy forest, rising sea levels will likely render the island uninhabitable by the species in the coming century (e.g. Williams 2013).

Conservation Actions [top]

Conservation Actions: Very little information is known about this newly discovered species. Hence, additional research is greatly needed with regard to the biology, ecology, and natural history of the species. Some acute conservation measures should be implemented based on what is presently known. These should include introduced species removal and habitat restoration of Conception Island, ex situ conservation, and ongoing monitoring. Habitat restoration of Conception Island should primarily include surveys for invasive vertebrates (e.g., Rattus, Felis). Mice (Mus) are presently documented on the island. Ex situ conservation should include the establishment of an “insurance colony” at an approved institution, accompanied by a Species Survival Plan or other actionable captive management plan. Ongoing research should include further studies of population trends and size, basic natural history, etc.

Citation: Reynolds, R.G. 2017. Chilabothrus argentum. The IUCN Red List of Threatened Species 2017: e.T118470875A118470877. . Downloaded on 24 March 2018.
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