Growth patterns of the Golden Lancehead and their determinants: Conservation strategies for critically endangered species

Abstract

The Golden Lancehead, Bothrops insularis, is a critically endangered viperid species, endemic to Queimada Grande Island. The diet of adults relies mainly on migratory birds, which peaks in March and July on the island. Herein, we describe the growth rate of the Golden Lancehead for the very first time, testing the hypothesis that growth and adult body size may decrease as a result of resource scarcity and environmental variability in the island, in comparison to a captive population. Our findings suggest that both food intake, temperature, and reproductive requirements might influence body size, growth rate, and sexual maturity of B. insularis. More specifically, wild animals attain smaller body size and mass, show lower growth rate, and attain sexual maturity later, in comparison to the captive individuals of the same sex, possibly as a result of lower food availability. This situation is more evident among males, and, apparently, morphological constraints make it difficult for them to explore large prey at the island. Females are the largest sex, possibly as a result of fecundity optimization. Fecundity also depends on energy reserve for vitellogenesis, and, due to the metabolic costs involved, females take a longer time to mature, showing, therefore, delayed maturity when compared to males. These aspects are especially important for conservation. Concerning species conservation, the impact of the larger body size in captive animals on other traits, such as habitat use, must be considered, especially if reintroduction of these animals become necessary. As for the Golden Lanceheads in the island, it is mandatory that the conservation strategies encompass the maintenance of the population of the migratory birds, in order to ensure the energetic income to the snakes.