Re-introduction of the American burying beetle to Nantucket Island, Massachusetts, USA

Summary

The American burying beetle (Nicrophorus americanus), federally endangered and reliant on 80-180 gram vertebrate carrion for reproduction, disappeared from Nantucket Island, Massachusetts by 1926 before the Roger Williams Park Zoo and Nantucket Maria Mitchell Association began an 18-year US Fish and Wildlife Service-supervised reintroduction, now the only successful reintroduction of the species in the country. Captive breeding, developed at Boston University and expanded at the zoo using founders from the natural Block Island, Rhode Island population, has produced over 5,000 beetles by pairing siblings-free adults in soil-filled containers with frozen-thawed quail or rat carcasses that beetles bury and prepare as larval food, tracked through an AZA studbook to preserve genetic diversity. Following a seven-year pilot release on Penikese Island that established a persisting population with no further stocking, Nantucket became the site of full-scale releases starting in 1994, with 2,923 beetles released over 13 years, achieving 50-70% successful brood-rearing per buried pair as verified by periodically exhuming and reburying a sample of broods. Trap-based monitoring of wild beetle numbers has generally increased year over year, and starting in 2011 the team began deliberately scaling back supplemental provisioning, from full support down to just 24% of captured beetles, to test whether the wild population can sustain itself unaided. Major difficulties included uncertain natural carrion availability, difficulty precisely estimating the reintroduced population, and short beetle activity seasons vulnerable to weather. The project rates itself Successful, while acknowledging that true self-sustaining status remains unconfirmed.