TY - JOUR
T1 - The challenge of preventing extinctions
T2 - lessons from managing threatened land snails on Norfolk Island
AU - Hyman, Isabel T.
AU - Van Sluys, Monique
AU - Foon, Junn Kitt
AU - Macgregor, Nicholas A.
AU - Anderson, Alexandra H.
AU - Patel, Tara
AU - Clow, Tarryn Williams
AU - Wilson, Melinda
AU - Daly, Andrew
AU - Bennison, Kerrie
AU - Bonson, Parnee
AU - Brown, Simon
AU - Christian, Brendon
AU - Finlayson, Brett
AU - Greenup, Nigel
AU - King, Lilli Unna
AU - Köhler, Frank
N1 - Publisher Copyright:
© 2024 Hyman et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
PY - 2024
Y1 - 2024
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85212689609&partnerID=8YFLogxK
U2 - 10.1371/journal.pone.0314300
DO - 10.1371/journal.pone.0314300
M3 - Article
C2 - 39680534
AN - SCOPUS:85212689609
SN - 1932-6203
VL - 19
JO - PLoS ONE
JF - PLoS ONE
IS - 12
M1 - e0314300
ER -
