The University of New South Wales, Sydney, New South Wales, Australia.
Arid Recovery, Roxby Downs, South Australia, Australia.
Conserv Biol. 2024 Jun;38(3):e14209. doi: 10.1111/cobi.14209. Epub 2024 Feb 11.
Reintroduced populations are typically considered to progress through establishment, growth, and regulatory phases. However, most reintroduction programs do not monitor intensively enough to test this conceptual model. We studied population indices derived from track activity of 4 threatened species (greater bilby [Macrotis lagotis], burrowing bettong [Bettongia lesueur], greater stick-nest rat [Leporillus conditor], and Shark Bay bandicoot [Perameles bougainville]) over 23 years after multiple reintroductions of each species in arid Australia. We compared population trajectories among species and investigated the effect of time and environmental variables. All species bred immediately after release, and the growth phase lasted 3-16 years, varying markedly among but not within species. The end of the growth phase was characterized by an obvious peak in population density followed by either a catastrophic decline and sustained low density (bettongs), a slow decline to extirpation after 20 years (stick-nest rat), or a slight decline followed by irregular fluctuations (bilby and bandicoot). Minor fluctuations were related to environmental variables, including 12-month cumulative rainfall and lagged summer maximum temperatures. Three of the 4 species did not reach a regulation phase, even after 23 years, possibly due to interspecific competition and trophic cascades triggered by predator removal and multispecies reintroductions. Bilbies and bandicoots exhibited a second growth phase 18 years after reintroduction, likely caused by high rainfall and increased resources following the population crash of overabundant bettongs. Our results suggest that assemblages within multispecies reintroductions demonstrate high variability in population trajectories due to interactive effects. Intensive monitoring to assess population viability may require decades, particularly where multiple species are reintroduced, release sites are confined, and the climate is unpredictable. Intensive monitoring also allows for adaptive management to prevent precipitous population declines. Practitioners should not assume reintroduced species pass through predictable postrelease population phases or that viability is assured after a certain period.
重新引入的种群通常被认为要经历建立、增长和监管阶段。然而，大多数重新引入计划并没有进行足够密集的监测来检验这一概念模型。我们研究了 4 种受威胁物种（大兔耳袋狸 [Macrotis lagotis]、穴兔袋狸 [Bettongia lesueur]、大竹鼠 [Leporillus conditor] 和鲨鱼湾袋狸 [Perameles bougainville]）在澳大利亚干旱地区多次重新引入后 23 年的足迹活动得出的种群指数。我们比较了物种之间的种群轨迹，并研究了时间和环境变量的影响。所有物种在释放后立即繁殖，增长阶段持续了 3-16 年，不同物种之间的差异显著，但同一物种内的差异不显著。增长阶段的结束以种群密度的明显峰值为特征，随后是灾难性下降和持续低密度（穴兔袋狸）、20 年后缓慢下降至灭绝（竹鼠），或轻微下降后不规则波动（兔耳袋狸和袋狸）。小的波动与环境变量有关，包括 12 个月的累积降雨量和滞后的夏季最高温度。4 个物种中有 3 个甚至在 23 年后仍未达到调控阶段，这可能是由于种间竞争和捕食者去除以及多种群重新引入引发的营养级联。兔耳袋狸和袋狸在重新引入 18 年后出现了第二个增长阶段，可能是由于过度丰富的穴兔袋狸种群崩溃后降雨量增加和资源增加所致。我们的结果表明，由于相互作用的影响，多种群重新引入的组合在种群轨迹上表现出高度的可变性。为了评估种群生存能力，需要进行密集监测，尤其是在多个物种被重新引入、释放地点受限且气候不可预测的情况下。密集监测还可以进行适应性管理，以防止种群急剧下降。从业者不应假设重新引入的物种会经历可预测的释放后种群阶段，也不应假设在一定时间后就可以保证其生存能力。
