Hyman Isabel T, Van Sluys Monique, Foon Junn Kitt, Macgregor Nicholas A, Anderson Alexandra H, Patel Tara, Williams Clow Tarryn, Wilson Melinda, Daly Andrew, Bennison Kerrie, Bonson Parnee, Brown Simon, Christian Brendon, Finlayson Brett, Greenup Nigel, King Lilli-Unna, Köhler Frank
Australian Museum Research Institute, Sydney, Australia.
Invertebrates Australia, Osborne Park, Australia.
PLoS One. 2024 Dec 16;19(12):e0314300. doi: 10.1371/journal.pone.0314300. eCollection 2024.
Norfolk Island, situated between Australia, New Zealand and New Caledonia, has a rich, narrowly endemic land snail fauna, which has suffered considerably from habitat loss and introduced predators. Eleven species (Stylommatophora, Microcystidae) are currently listed by the IUCN and/or Australia's EPBC Act 1999 as Endangered, Critically Endangered or Extinct. Based on targeted surveys undertaken since 2020, we re-assess the threat status of these taxa. For three species assessed to be at imminent risk of extinction, we report on the implementation of in-situ and ex-situ conservation actions and assess their effectiveness after a three-year period. We document current distributions and abundances of these species and describe experimental conservation methods, such as increased predator control, the erection of predator-proof exclosures, and the establishment of an ex-situ breeding population. We found that the relative abundance of one subspecies, Advena campbellii campbellii, was strongly correlated with monthly rainfalls. Trials of predator-proof exclosures that retain adults but allow juveniles to disperse indicated that snails can be successfully secured from predation. Increased efforts in predator control led to the killing of more rodents and chickens; however, the impact on the snail population is unclear. The ex-situ breeding population had high birth rates initially followed by high adult mortality. Adjustments in husbandry conditions reduced stress levels leading to sustainable birth rates and increased survivorship with the result of rapid population growth. We determined that the ovoviviparous A. campbellii campbellii matures at the age of 3-4 months and has a lifespan of 10-12 months in captivity. We conclude that focused predation studies are needed to determine the impact of introduced predators. The use of exclosures requires further refinement especially regarding feeding schedules. In-situ breeding requires significant time for establishment but can be implemented successfully. We assess three endemic species as Extinct, four as Critically Endangered and two as Vulnerable.
诺福克岛位于澳大利亚、新西兰和新喀里多尼亚之间，拥有丰富的、狭域分布的特有陆地蜗牛动物群，但该动物群因栖息地丧失和外来捕食者的引入而遭受了严重影响。目前，国际自然保护联盟（IUCN）和/或澳大利亚1999年的《环境保护与生物多样性保护法》（EPBC Act）将11种蜗牛（柄眼目，微囊科）列为濒危、极度濒危或灭绝物种。基于2020年以来开展的针对性调查，我们重新评估了这些分类群的受威胁状况。对于三种被评估为面临迫在眉睫的灭绝风险的物种，我们报告了就地和迁地保护行动的实施情况，并在三年后评估了其有效性。我们记录了这些物种当前的分布和数量，并描述了实验性的保护方法，如加强捕食者控制、建造防捕食者围栏以及建立迁地繁殖种群。我们发现，一个亚种——坎氏阿文螺坎贝尔亚种（Advena campbellii campbellii）的相对丰度与月降雨量密切相关。对能留住成年个体但允许幼体扩散的防捕食者围栏进行的试验表明，蜗牛能够成功避免被捕食。加强捕食者控制的努力导致捕杀了更多的啮齿动物和鸡；然而，对蜗牛种群的影响尚不清楚。迁地繁殖种群最初出生率很高，随后成年个体死亡率也很高。饲养条件的调整降低了压力水平，从而实现了可持续的出生率，并提高了存活率，结果是种群迅速增长。我们确定，卵胎生的坎氏阿文螺坎贝尔亚种在3 - 4个月龄时成熟，圈养寿命为10 - 12个月。我们得出结论，需要开展有针对性的捕食研究，以确定外来捕食者的影响。防捕食者围栏的使用需要进一步完善，特别是在喂食时间表方面。就地繁殖需要很长时间才能建立起来，但可以成功实施。我们评估三种特有物种为灭绝，四种为极度濒危，两种为易危。
