Research Institute for the Environment and Livelihoods, College of Engineering, IT and Environment, Charles Darwin University, Darwin, NT, Australia.
Australian Institute of Marine Science, Darwin, NT, Australia.
Biol Lett. 2022 Apr;18(4):20210676. doi: 10.1098/rsbl.2021.0676. Epub 2022 Apr 27.
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 C and N in bones of crocodiles sampled 40 to 55 years ago (small population) with bones from contemporary individuals (large population). We found that C and N values were significantly lower in contemporary crocodiles than in 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 number of feral pigs consumed to sustain and grow crocodile biomass may help suppress pig population growth and increase the flow of terrestrially derived nutrients into aquatic ecosystems. The study highlights the significance of prey availability in contributing to large carnivore population recovery.
支持大型食肉动物的恢复是一项受欢迎但具有挑战性的工作。澳大利亚的咸水鳄是大型食肉动物保护的成功案例，其数量从过去的大量开发中广泛恢复。在这里，我们通过比较 40 至 55 年前（小种群）和当代个体（大种群）取样的鳄鱼骨骼中的 C 和 N 同位素，探讨了这种大型种群恢复是否伴随着饮食变化。我们发现，与历史群体相比，当代鳄鱼的 C 和 N 值明显较低，这表明它们的猎物偏好已经从海洋转向陆地食物网。我们提出，在恢复中的鳄种群中，种内竞争的增加，以及占据洪泛平原的野生动物有蹄类动物的增加，可能导致鳄种群转向主要以陆地食物为食。为维持和增加鳄生物量而消耗的野猪数量可能有助于抑制猪群的生长，并增加陆地来源的营养物质流入水生生态系统。该研究强调了猎物可用性在促进大型食肉动物种群恢复方面的重要性。
