Nactus pelagicus (Girard, 1852)
Family: Gekkonidae Pacific Slender-toed Gecko Status: Indigenous Description: This is a medium sized to large species of gecko with a relatively large head. Adults range from 40 up to 70.5 mm SVL (Zug and Moon 1995). The dorsal surface of the body and tail has rows of distinct tubercles. Unlike all other geckos in the region, this species lacks enlarged toe-pads. The dorsal coloration is grey to brown with a series of darker chevrons down the back. The lips are pale with dark vertical bars. Like other geckos in the region this gecko appears paler at night, however, it does not undergo the dramatic shift in coloration and pattern that can be seen in other geckos. The exception to this is the bold vertical bars on the lips that virtually disappear at night. The proportionally large head, tuberculate skin, and lack of toe-pads will distinguish this gecko from all others in the region. Biology: This is another all female species of gecko that reproduces asexually. This species is most common in areas with abundant terrestrial retreats. It is most often encountered in forest with large trees and a rocky substrate, but can also be found in riverine forest with an abundance of leaf litter and woody debris. On Pagan Island it is common on the barren lava flows, and this is the only habitat in which it was detected. On Guam, N. pelagicus appears to exist in localized populations and there are large areas of apparently suitable habitat that seem to be uninhabited by this gecko. At night this gecko is usually observed on large diameter trees and rocks within a meter of the ground though individuals are also seen on the ground and higher in the trees. It is easily disturbed by lights and it quickly flees to the nearest retreat, often a hole at the base of the tree or rock upon which it’s perched. If undisturbed, geckos can be observed perched on the same rock or trunk several nights in a row. This gecko appears to be particularly vulnerable to predation by the introduced shrew Suncus marinus and is thought to be extirpated from the islands of Saipan and Tinian where the shrew is common. Ironically, this gecko’s persistence on Guam may be due in part to the presence of the brown treesnake which has played a significant role in the extirpation and extinction of many of Guam’s other native terrestrial vertebrates. The snake also preys on the shrews and may keep populations suppressed (Rodda and Fritts 1996). Distribution: This species occurs widely throughout Oceania and the islands of the western Pacific (Zug and Moon 1995). In the Mariana Islands, Nactus pelagicus occurs on Guam, Rota, Anatahan, Sarigan (Vogt and Williams 2004) and Pagan (Reed et al. 2010). It would not be surprising if it were found on the rest of the larger islands. Reed R. N., G.H. Rodda, S.R. Siers, E. Wostl, A. Yackel Adams. 2010. Terrestrial Reptiles of Pagan Island, Commonwealth of the Northern Mariana Islands. Report to USFS. Rodda G. H. and T. Fritts. 1996. Reptiles of the Ordinance Annex, Naval Activities Guam. Prepared for U.S. Fish and Wildlife Service, Honolulu HI. Vogt, S. and L. Williams. 2004. Common Flora and Fauna of the Mariana Islands. Zug, G.R. and B.R. Moon. 1995.Systematics of the Pacific Slender-Toed Geckos, Nactus pelagicus complex: Oceania, Vanuatu, and Solomon Islands Population. Herpetologica, 51 (1) 77-90 |