Spatiotemporal variation in Lepidochelys olivacea sea turtle nests and their influence on the abundance and reproductive phenology of the sapro-necrophagous beetle Omorgus suberosus.

Abstract

The olive ridley sea turtle, Lepidochelys olivacea (Eschscholtz, 1829), nests en masse in the protected natural area of La Escobilla, Mexico. On this beach, Omorgus suberosus (Fabricius, 1775), a sapro-necrophagous beetle, feeds on the sea turtles' decomposing and live eggs and is considered to be a threat for the conservation of L. olivacea. However, the abundance and reproductive phenology of O. suberosus in relation to the spatial and temporal availability of this food resource are unknown. We tested two alternative hypotheses during the 2013-2014 nesting season of L. olivacea: (i) abundance and female reproductive phenology of beetles are determined by the spatial and temporal availability of decomposing eggs that accumulate during the turtle nesting season, and (ii) abundance and female reproductive phenology of beetles are related to the increase in the concentration of seasonal and/or new turtle nests. Twenty-four plots (1m2) were sampled in three areas with different turtle nesting densities. Spatially, beetle abundance was greater where turtle nest density was high and decomposed eggs were abundant. At the temporal level, old nests (> 45days after egg deposition) were abundant and the presence of seasonal and new nests (~ 45 or fewer days after egg deposition) appeared to trigger sexual maturation in female beetles. Immature female beetles were more abundant throughout the turtles' nesting season, and mature females were only abundant during the turtle arribadas with the highest number of seasonal nests. We conclude that abundance and female reproductive phenology of O. suberosus females are influenced by the quantity and quality of the resource. These findings are useful to understand the interaction of L. olivacea with other species and to strengthen the conservation plans of this turtle species.