School of Biological Sciences, Queen's University Belfast, Belfast, UK.
Institute of Global Food Security (IGFS), Queen's University Belfast, Belfast, UK.
Integr Zool. 2021 Mar;16(2):240-254. doi: 10.1111/1749-4877.12497. Epub 2020 Dec 4.
According to the International Union for Conservation of Nature Red List, 41% of the world's amphibian species are threatened with extinction, making them more threatened than any other vertebrate group nowadays. Given the global amphibian crisis, comprehensive understanding of demographics and population trends of declining and threatened species is essential for effective management and conservation strategies. Counting egg spawns is widely used to assess population abundance in pond breeding anurans. However, it is unknown how such counts translate into robust population size estimations. We monitored the breeding activity of the Natterjack toad (Epidalea calamita), combining egg string counts and individual photo-identification with Capture-Mark-Recapture population size and operational sex ratio estimation. Male Natterjack toads were identified by the pattern of natural markings with repeated ID of the same individual confirmed for 10% of the samples using genetic fingerprinting. We identified 647 unique individuals within a closed study population at Caherdaniel, Co Kerry. Population estimates derived from egg string counts estimated a breeding population of 368 females (95% CI 353-384) and Capture-Mark-Recapture estimated a breeding population of 1698 males (95% CI 1000-2397). The female:male sex ratio was conservatively estimated at 1:5 (95% CI 1:3-1:6) where 62% ± 6% of females were assumed to spawn. These substantially departed from any priori assumption of 1:1 which could have underestimated the breeding population by up to 72%. Where amphibian absolute population size estimation is necessary, methods should include empirical survey data on operational sex ratios and not rely on assumptions or those derived from the literature which may be highly population and/or context-dependent.
根据国际自然保护联盟的红色名录，全球 41%的两栖物种面临灭绝威胁，比当今任何其他脊椎动物群体都更受威胁。鉴于全球两栖动物危机，全面了解数量减少和濒危物种的人口趋势对于制定有效的管理和保护策略至关重要。 计数卵是广泛用于评估池塘繁殖蛙类种群丰度的方法。然而，目前尚不清楚这种计数如何转化为可靠的种群规模估计。我们监测了欧洲林蛙（Epidalea calamita）的繁殖活动，将卵串计数与个体照片识别与捕获-标记-重捕种群规模和操作性别比估计相结合。通过对个体的反复识别和遗传指纹确认，可根据个体天然标记的图案识别雄蛙，我们在凯里郡的卡赫达尼尔（Caherdaniel）的一个封闭研究种群中识别了 647 个独特个体。 卵串计数估计的繁殖种群有 368 只雌蛙（95%置信区间 353-384），而捕获-标记-重捕估计的繁殖种群有 1698 只雄蛙（95%置信区间 1000-2397）。雌性：雄性性别比保守估计为 1:5（95%置信区间 1:3-1:6），其中 62%±6%的雌蛙被假定产卵。这与任何先验假设的 1:1 相差甚远，这可能会导致繁殖种群被低估多达 72%。在需要对两栖动物的绝对种群规模进行估计时，方法应该包括关于操作性别比的经验调查数据，而不应依赖于假设或可能高度依赖于种群和/或背景的文献推导数据。
