SKINKS BENEATH THE SUBSTRATE: NEOICHNOLOGY OF THE GOLDEN SKINK MABUYA MULTIFASCIATA

With over 1,200 extant species, skinks are the most diverse group of lizards. While most skink species are either ground dwellers or burrowers, little is known about their biogenic structures. In this project, the biogenic structures produced by the burrowing skink Mabuya multifasciata were studied in laboratory-based neoichnological experiments in order to aid in the interpretation of continental ichnofossils. Mabuya multifasciata is an exclusively tropical, medium-sized skink whose range includes southern China, Malaysia, and the Philippines. The objectives of this research were to determine the morphology of the biogenic structures produced by ground-dwelling skinks as well as to evaluate the effects of environmental factors, such as sediment density and moisture content, on the burrowing behaviors and resulting biogenic structures. Individual specimens of M. multifasciata were placed in 10 and 30 gallon terrariums that contained massive, organic-rich sediment. The specimens were exposed to variations in sediment density and moisture content within the normal range of the species. The density of the sediment was increased with the addition of clay and decreased with the addition of sand. The sediment moisture content was held constant at 20, 40 and 60%. Specimens of M. multifasciata burrowed through intrusion while engaged in dwelling, escape, and predation behaviors. They produced a diverse array of burrow morphologies including several types of ramps, U-shaped, and J-shaped burrows with circular to elliptical cross sections. The majority of the burrows possessed several randomly spaced, triangular divots along the tunnel walls. Burrows produced in high density sediments had reduced average widths and width-to-height ratios while burrows produced in high moisture sediments had greater maximum depths and complexities. Bray Curtis similarity analyses indicated that all of the M. multifasciata burrows were similar to each other based on 10 quantitative parameters. The results of this laboratory study will allow for the recognition of biogenic structures produced by skinks, aid in the interpretation of the paleoenvironmental conditions in which similar biogenic structures were produced, and assist in the understanding of the role of small reptiles in pedogenesis in tropical environments.