Relative Abundance of Lizards and Marine Toads on Saipan, Mariana Islands

Twelve species of lizards and the marine toad (Bufo marinus L.) were surveyed in six habitat types at three sites on the island of Saipan, Mariana Islands, using visual censuses, hand captures, and adhesive traps. Toads were rare on each of the study sites. Anolis carolinensis Cuvier was most common in disturbed forests. Four species of geckos, Gehyra mutilata (Wiegmann), G. oceanica (Lesson), Lepidodactylus lugubris (Dumeril & Bibron), and Perochirus ateles Dumeril, were most abundant in forests and abandoned buildings, and a fifth species, Hemidactylus frenatus Dumeril & Bibron, occurred most frequently on structures of all types and in open fields. The skink Carlia fusca Dumeril & Bibron was the most abundant diurnal lizard in all habitats. Emoia caeruleocauda de Vis occurred in all habitat types surveyed except open fields and was usually much less common than C. fusca. Emoia atrocostata (Lesson) was documented for the first time on Saipan, with a population found on a small offshore islet with scrubby strand vegetation. Lamprolepis smaragdina (Lesson) was relatively common at only one of three study sites, where it was seen primarily on large tree trunks. Varanus indicus (Daudin) displayed broad habitat use, but also was common in only one study area. At least five of these species are introductions, with C. fusca suspected of causing population reductions of other terrestrial skinks on the island. INCREASING AlTENTION has been focused on the diversity, abundance, and ecology of reptile and amphibian communities in the Mariana Islands of Micronesia (Sabath 1981, Wiles et al. 1989, 1990b, Rodda et al. 1991, Rodda and Fritts 1992). However, no studies have examined the herpetofauna of Saipan, which is the second largest and second most populous island in the archipelago. A better understanding of the reptiles on the island is desirable because of accelerated habitat loss associated with recent economic growth and the island's high risk of obtaining a breeding population of brown tree snakes [Boiga irregularis (Merrem)]. Saipan's reptile fauna is also of interest because of the introduction of several lizard species during the last few decades (Rodda et al. 1991). One of these 1 Manuscript accepted 25 October 1995. 2 Division of Aquatic and Wildlife Resources, 192 Dairy Rd., MangiJao, Guam 96923. species, the skink Carlia fusca Dumeril & Bibron, has been implicated in the declines of native skinks elsewhere in the island chain (Rodda et al. 1991). Finally, most of Saipan is occupied by highly disturbed vegetation, which likely has altered its lizard populations. Native plant communities currently cover less than 8% of the island (Engbring et al. 1986). The goals of our study were to document lizard and marine toad (Bufo marinus L.) abundance and habitat use at several locations on Saipan.