Impact of food availability on the length-weight allometry of the slender forest skink (Scincella modesta) in a subtropical urban forest

Lizards are important reptiles to global terrestrial ecosystems but are vulnerable to habitat loss. The relationships between body size and weight of lizards follow species-specific allometric equations that reflect growth patterns and life-history strategies. The slender forest skink ( Scincella modesta ) is a small-sized oviparous skink endemic to and protected in China. Feeding on arthropods, it is under the threats of decreasing arthropod abundance due to human disturbances in its habitats, e.g., deforestation and urbanization. However, there is little understanding how arthropod abundance might affect its growth pattern and life-history strategy. In this study, we sampled 93 individuals of the S. modesta from 61 sites in a 32-hectare subtropical urban forest, and collected 13,397 ground arthropods from these sites. We then incorporated arthropod abundance into the allometric equation between snout-vent length and weight of the 93 skinks. The parameterized model shows that, at a parity of body sizes, the skinks at the sites with fewer arthropods are heavier than those with more arthropods. Selection pressure for food is likely associated with the additional energy invested in gaining weight by S. modesta in the study area, which reduces their available energy for escape and reproduction. The results suggest that maintaining arthropod abundance and protecting forest habitats are essential for conserving this endemic lizard species in China.