Dietary shifts may underpin the recovery of a large carnivore population

Supporting the recovery of large carnivores is a popular yet challenging endeavour. Estuarine crocodiles in Australia are a large carnivore conservation success story, with the population having extensively recovered from past heavy exploitation. Here, we explored if dietary changes had accompanied this large population recovery by comparing the isotopes δ13C and δ15N in bones of crocodiles sampled 40 to 55 years ago (small population) with bones from contemporary individuals (large population). We found that δ13C and δ15N values were significantly lower in contemporary crocodiles compared to the historical cohort, inferring a shift in prey preference away from marine and into terrestrial food webs. We propose that an increase in intraspecific competition within the recovering crocodile population, alongside an increased abundance of feral ungulates occupying the floodplains, may have resulted in the crocodile population shifting to feed predominantly upon terrestrial food sources. The ...助力大型食肉动物种群恢复是一项广受关注却极具挑战的工作。澳大利亚河口鳄（Estuarine crocodile）是大型食肉动物保护领域的成功典范，其种群已从过去的过度捕猎中全面恢复。本研究通过对比40至55年前（彼时种群规模较小）采集的鳄骨与当代个体（当前种群规模较大）的碳同位素δ¹³C与氮同位素δ¹⁵N值，探究该种群大规模恢复过程中是否伴随食性改变。研究发现，当代河口鳄的δ¹³C与δ¹⁵N值显著低于历史种群，由此推断其猎物偏好已从海洋食物网转向陆地食物网。我们推测，恢复中的河口鳄种群种内竞争加剧，加之泛滥平原上野生有蹄类动物种群数量增多，可能促使该种群转向以陆地食物来源为主要捕食对象。……