Ecology, natural history, and conservation status of Scolopendra abnormis, a threatened centipede endemic to Mauritius

Abstract

The Serpent Island centipede Scolopendra abnormis is a threatened centipede species found on only 2 small islands in the Indian Ocean: Round Island, located 22.5 km northeast of Mauritius, and Serpent Island, 4 km northwest of Round Island. Current understanding of its ecology is based on limited direct observations from 30 yr ago. Round Island has since undergone significant habitat restoration. Hyperabundant non-native ants are also present, which may impact centipede nesting behaviour, ecology, and survival. Recent methodological advances, such as high-throughput sequencing of dietary DNA, can extend our understanding of invertebrate ecology and provide data complementary to direct observation. Using a combination of dietary metabarcoding and observational approaches, we provide new insights into the ecology and natural history of this threatened invertebrate predator. S. abnormis nest most consistently in the root network found beneath endemic Pandanus vandermeeschii trees. They are also found in areas with good soil cover, herbaceous growth, and areas of bare rock slab. Only 4 of 43 centipedes in this study were found near an ant foraging trail, which may have significant implications for S. abnormis nesting habits. These centipedes primarily consume insect prey (particularly taxa within Lepidoptera, Hymenoptera, Diptera), irrespective of centipede body size. A quarter of centipedes also consumed endemic lizards. We also found marked differences in diet composition between wet and dry seasons arising from the changing availability of prey. We provide additional natural history observations and conclude by suggesting conservation actions that would help better understand and safeguard S. abnormis populations.