Oryx Vol 35 No 4 October 2001 Threats to the Critically Endangered endemic Bermudian skink Eumeces longirostris John Davenport, Jeremy Hills, Anne Glasspool and Jack Ward Abstract The Bermudian rock lizard or skink Eumeces inated by large, old (some possibly >27 years) animals longirostris is categorized as Critically Endangered on that exhibit high mutilation rates. Breeding occurs, but the 2000 IUCN Red List. Skinks are vulnerable to habitat survival to adulthood appears poor. All of neighbouring loss, introduction of non-native species and mortality Southampton Island was intensively trapped, with traps caused by discarded bottles and cans that act as self- placed at the intersections of a 10-m grid. The popula- baiting traps. This study describes the population tion was estimated by mark-recapture trials to be c. 400 characteristics of the Bermudian skink on two islands adults and juveniles; hatchlings are insectivorous and of the Bermudian archipelago: Nonsuch and Southamp- not susceptible to trapping. The population on Sou- ton islands. Nonsuch Island is a nature reserve but has thampton Island is currently the largest known on populations of introduced lizards of the genus Anolis, Bermuda and appears to be viable; sustained isolation lizard-eating birds and (a new finding) the cane toad from predators and people is essential to its mainten- Bufo marinus. Southampton Island is relatively isolated ance. and has no introduced species. The skink population on Nonsuch Island was not investigated in detail, but Keywords Bermuda, Critically Endangered lizards, appears to be small, localized to human habitation Eumeces longirostris, skinks. (where cover and food scraps are available) and dom- Introduction (pers. comm.) has a photograph of a dissected skink with six eggs. Taken together these observations suggest The Bermudian rock lizard or skink Eumeces longirostris that breeding takes place each year in the summer and is the only endemic terrestrial vertebrate on the isolated that clutch size is 5-6. However, there is no indication of archipelago of Bermuda. It is a relatively primitive whether females lay clutches every year, or more than 'relict' species of the widespread genus Eumeces (Taylor, once in a season. 1936), identifiable on Bermuda from Pleistocene depos- The species' lifespan is essentially unknown, although its (Wingate, 1965), but probably resident for hundreds some skink species are known to survive in captivity for of thousands of years. The closest relative appears to be many years - an experimental colony (n ~ 100) of E. fasciatus of south-eastern USA (Heilprin, 1889). similarly sized desert skinks Chalcides ocellatus from The Bermudian skink is poorly known, except in those Egypt showed no adult mortality during a 12-year features amenable to direct observation. Notes on period (J. Davenport, pers. obs.). H. Griffith, D.B. reproduction were made from five skinks kept in Wingate & D.L. Robinson (unpublished data) used toe- captivity at Bermuda Aquarium, Museum and Zoo clipping in studies on Nonsuch Island (Fig. 1) during since 1984. Three hatchlings were 'discovered' in the the 1960s, but abandoned these in 1970. Several large terrarium in August 1984, seven skinks hatched in July- lizards collected in the present study were missing toes, August 1985, and in July 1986 a nest of five eggs was suggesting that individuals may live more than discovered under a rock and shortly thereafter a 27 years. It is not known when Bermudian skinks hatchling was seen (Barnes & Eddy, 1987). R. Marirea become sexually mature or what their growth rates are. Another captive colony is to be established by the J. Davenport (Corresponding author) University Marine Biological Bermuda Aquarium, Museum of Natural History and Station, Millport, Isle of Cumbrae, UK; Present address: Department of Zoo, and if successful, some of these basic questions Zoology and Animal Ecology, University College Cork, Lee Maltings, may be answered. Prospect Row, Cork, Ireland. E-mail: [email protected] Colouration of Bermudian skinks changes markedly J. Hills University Marine Biological Station, Millport, Isle of Cumbrae, during development. Recently hatched skinks ('hatch- UK lings') have sky blue tails and striped bronze, cream and A. Glasspool and J. Ward Bermuda Aquarium, Natural History Museum chocolate bodies. Juvenile and subadult animals pro- and Zoo, PO Box FL 145, Flatts, FL BX, Bermuda gressively lose first the blue coloration of the dorsal tail Revised manuscript accepted for publication 3 July 2001 332 © 2001 FFI, Oryx, 35(4), 332-339 Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.76, on 26 Sep 2021 at 09:00:34, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1046/j.1365-3008.2001.00200.x Threats to the Bermudian skink 333 64°42' 64°48' O 32=24'- 32 24' 32°18'- Pear Island ^ Green Tom's Rock > Rock Castle Island "y- - "^Southampton Castle Point Island 'Charles Island 0.5 1 km 4 km Bird Rock Rushy Island 64°42' 64°48' Fig. 1 Bermuda, with parishes, showing locations of islands mentioned in the text. surface, then the bronze dorsal colour and stripes, and occurrence <100 sq km or area of occupancy <10 sq km acquire an orange chin and cheeks. Apparently fully (B), severely fragmented (1), and with continued decline adult animals have dark upper surfaces (marbled tan or (2), in area of occupancy (b), in area, extent and/or blue or black), a blue belly and an orange chin and quality of habitat (c), in number of locations or subpopu- cheeks. We emphasize that 'hatchling', 'juvenile', 'sub- lations (d), and in number of mature individuals (e). adult' and 'adult' are imprecise terms; the duration of However, there is no specific legislative protection for each stage is unknown, and it is unclear whether 'adults' the skink, although island beaches are equipped with are the only sexually mature stages. litter bins, notices explain the risks posed by discarded The Bermudian skink is believed to be strictly insec- drink containers, and poster campaigns raise awareness tivorous as a hatchling, but juveniles, subadults and in schools. The Bermuda Biodiversity Strategy and adults also take substantial quantities of carrion, espe- Action Plan is being prepared and coordinated by the cially that associated with sea bird nests (in particular Bermuda Zoological Society, supported through the UK the cahow Pterodroma cahozv and the white-tailed tropic Darwin Initiative. bird or longtail Phaethon lepturus). Carrion taken Once common throughout Bermuda (Wingate, 1965), includes broken eggs, dead chicks, and regurgitated skink populations have declined throughout the archi- fish and squid (Wingate, 1965; Garber, 1988; pelago, although Wingate thought the species more D.B. Wingate, pers. comm.). common inland than generally recognized (disputed by The Bermudian skink is listed as Critically Endan- Garber (1988), who believed the skink to have been rare gered on the 2000 IUCN Red List (Conyers, 1996; Hilton- for many years). Habitat loss has undoubtedly been a Taylor, 2000), based on criteria Bl + 2bcde, i.e. extent of factor over much of the archipelago. The native habitat © 2001 FFI, Oryx, 35(4), 332-339 Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.76, on 26 Sep 2021 at 09:00:34, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1046/j.1365-3008.2001.00200.x 334 J. Davenport et al. of forests and swamps has largely been replaced by agement of the species. The report from the present agriculture, which covers 17 per cent of the archipelago, study was regarded as a key first step towards design of and homes and gardens, which occupy 50 per cent of a full management plan. Preliminary work was carried land area (Thomas & Logan, 1992). out on Nonsuch Island to determine whether the A study in the early 1990s by H. Griffith, D.B. Wingate population decline there was continuing and to test & D.L. Robinson (unpublished data) on Nonsuch Island survey techniques. (Fig. 1), a nature reserve (6.8 ha) with restored natural vegetation, revealed evidence of a serious population Methods decline over a 20-year period despite habitat loss not being a contributory factor. The decline has been Nonsuch Island (Fig. 1) has extensive restored natural attributed to predation by introduced and reintroduced Bermudian vegetation, is a nature reserve, and is visited species (D.B. Wingate, pers. comm.). These include by relatively large numbers of people. Southampton kiskadees (Pitangus sulphuratus, lizard-eating birds Island, to the south-west (Fig. 1), is barren and water- deliberately introduced in 1957 to control anoles but less by comparison and, because access is difficult, often observed to take skinks), night herons (Nyctanassa visitors are few. Except in a narrow band of bare rocky violacea, reintroduced to replace long-extinct native coast, the island supports extensive crab grass Steno- herons in 1976-78 and observed to regurgitate skink taphrum secundatum interspersed with Spanish bayonet remains in pellets) and Jamaican anoles (Anolis grahami, Yucca aloifolia, prickly pear Opuntia dilleni, seaside introduced in 1905 to control scale insects on crops and goldenrod Solidago sempervirens, lantana Lantana invo- seen to prey on young skinks (D.B. Wingate, unpub- lucrata and Bermudiana Sisyrinchium bermudiana. The lished data)). Other than night herons and a fossil hawk only shade is provided by a few scattered mixed bay there appear to have been no native skink predators on grape Coccoloba uvifera and tamarisk Tamarix gallica pre-colonial Bermuda. It is worth noting that Cope stands. Potentially predatory bird life is largely limited (1861), writing before the introduction of any other to the occasional kiskadee. At the southern end of the reptiles or amphibians but after much habitat loss, island is Southampton Fort, built shortly after Ber- described the skink as 'very common', but Verrill (1902) muda's colonization in 1612.