The prehistory of terrestrial reptiles and birds in the Central Lau Group, Fiji

Abstract

We identified nearly 1000 bones of reptiles and birds from 20 prehistoric sites in caves and rockshelters on four islands (Lakeba, Nayau, Aiwa Levu, and Aiwa Lailai) in the Lau Group of Fiji. The bones are Late Holocene in age (ca. 2800 to 200 years old) and are contemporaneous with prehistoric human habitation of the islands. They represent 32 species (7 reptiles, 25 non-passerine landbirds). Six of the seven taxa of squamate reptiles recovered from the prehistoric sites are indigenous to the Lau Group, including an undescribed and presumably extinct species of gekkonid lizard. While the Lau islands have never been surveyed comprehensively for modern squamate reptiles, six other species of lizards known to occur in Lau today are not represented with certainty in any of the bone deposits (the geckos Hemidactylus frenatus and Lepidodactylus lugubris, and skinks Emoia cyanura, E. impar, Cryptoblepharus eximius, and Lipinia noctua). Except for C. eximius, these synthropic and not necessarily native species are widespread on Pacific islands, with much or all of their dispersal being due to human agency. For landbirds, the prehistoric bones increase the species richness values from 21 to 29 species on Lakeba, from 17 to 19 species on Nayau, from 18 to 26 on Aiwa Levu, and from 16 to 17 on Aiwa Lailai. The extinct species of birds consist of two megapodes (Megapodius alimentum, M. amissus), two flightless rails (Gallirallus undescribed sp., Porzana undescribed sp.), and a pigeon (Ducula lakeba). Three living species of birds recorded pre-historically, but that no longer occur on these islands, are characteristic of freshwater habitats: the heron Butorides striatus and two volant rails, Porzana tabuensis and Poliolimnas cinereus. Three other extant species recorded from bones on Lakeba, but that no longer inhabit that island or any others in Lau, are the pigeon Didunculus cf. strigirostris, parrot Prosopeia sp., and lorikeet ?Charmosyna amabilis. Much of the inter-island differences in total species richness of birds (modern + prehistoric) is probably due to uneven sampling of prehistoric bones, which are both older (on average) and more abundant on Lakeba and Aiwa Levu than on the other two islands. Reconstructing the composition of the reptile and bird communities as they existed at first human contact demonstrates the unappreciated species richness of very small islands, a concept of interest to biogeographers and conservation biologists.