Spencer R-J, Van Dyke J U, Thompson Michael B
School of Science and Health, Hawkesbury Institute for the Environment, Western Sydney University, Building M15, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW 2751, Australia.
School of Life and Environmental Sciences, University of Sydney, Heydon-Laurence Building (A08), Sydney, NSW 2006, Australia.
Conserv Biol. 2017 Dec;31(6):1340-1349. doi: 10.1111/cobi.12930.
Ex situ conservation tools, such as captive breeding for reintroduction, are considered a last resort to recover threatened or endangered species, but they may also help reduce anthropogenic threats where it is difficult or impossible to address them directly. Headstarting, or captive rearing of eggs or neonate animals for subsequent release into the wild, is controversial because it treats only a symptom of a larger conservation problem; however, it may provide a mechanism to address multiple threats, particularly near population centers. We conducted a population viability analysis of Australia's most widespread freshwater turtle, Chelodina longicollis, to determine the effect of adult roadkill (death by collision with motor vehicles), which is increasing, and reduced recruitment through nest predation from introduced European red foxes (Vulpes vulpes). We also modeled management scenarios to test the effectiveness of headstarting, fox management, and measures to reduce mortality on roads. Only scenarios with headstarting from source populations eliminated all risks of extinction and allowed population growth. Small increases in adult mortality (2%) had the greatest effect on population growth and extinction risk. Where threats simultaneously affected other life-history stages (e.g., recruitment), eliminating harvest pressures on adult females alone did not eliminate the risk of population extinction. In our models, one source population could supply enough hatchlings annually to supplement 25 other similar-sized populations such that extinction was avoided. Based on our results, we believe headstarting should be a primary tool for managing freshwater turtles for which threats affect multiple life-history stages. We advocate the creation of source populations for managing freshwater turtles that are greatly threatened at multiple life-history stages, such as depredation of eggs by invasive species and adult mortality via roadkill.
迁地保护手段，如用于重新引入的圈养繁殖，被视为恢复受威胁或濒危物种的最后手段，但在难以或无法直接解决人为威胁的情况下，它们也可能有助于减少这些威胁。提前放生，即圈养卵或新生动物随后放归野外，存在争议，因为它只解决了一个更大的保护问题的症状；然而，它可能提供一种应对多种威胁的机制，特别是在人口中心附近。我们对澳大利亚分布最广的淡水龟——长吻蛇颈龟（Chelodina longicollis）进行了种群生存力分析，以确定成年龟因道路致死（与机动车碰撞死亡）的影响，这种情况正在增加，以及引入的欧洲赤狐（Vulpes vulpes）对巢穴的捕食导致幼龟数量减少的影响。我们还对管理方案进行了建模，以测试提前放生、狐狸管理以及减少道路死亡率措施的有效性。只有从源种群进行提前放生的方案消除了所有灭绝风险，并实现了种群增长。成年龟死亡率小幅上升（2%）对种群增长和灭绝风险的影响最大。当威胁同时影响其他生活史阶段（如幼龟数量补充）时，仅消除对成年雌龟的捕捞压力并不能消除种群灭绝的风险。在我们的模型中，一个源种群每年可以提供足够的幼龟来补充25个其他类似规模的种群，从而避免灭绝。基于我们的研究结果，我们认为提前放生应该是管理淡水龟的主要手段，因为这些龟面临的威胁会影响多个生活史阶段。我们主张为管理在多个生活史阶段受到严重威胁的淡水龟建立源种群，比如外来物种对卵的捕食以及道路致死导致的成年龟死亡。
