Warret Rodrigues Chloé, Angin Baptiste, Besnard Aurélien
Office National de la Chasse et de la Faune Sauvage Cellule Technique des Antilles françaises Trois-îlets France.
Department of Biological Sciences University of Manitoba Winnipeg Canada.
Ecol Evol. 2021 Sep 15;11(19):13068-13080. doi: 10.1002/ece3.8021. eCollection 2021 Oct.
In long-lived species, although adult survival typically has the highest elasticity, temporal variations in less canalized demographic parameters are the main drivers of population dynamics. Targeting recruitment rates may thus be the most effective strategy to manage these species. We analyzed 1,136 capture-recapture histories collected over 9 years in an isolated population of the critically endangered Lesser Antillean iguana, using a robust design Pradel model to estimate adult survival and recruitment rates. From an adult population size estimated at 928 in 2013, we found a yearly decline of 4% over the 8-year period. As expected under the canalization hypothesis for a long-lived species, adult survival was high and constant, with little possibility for improvement, whereas the recruitment rate varied over time and likely drove the observed population decline. We then used a prospective perturbation analysis to explore whether managing the species' immature cohorts would at least slow the population decline. The prospective perturbation analysis suggested that a significant and sustained conservation effort would be needed to achieve a recruitment rate high enough to slow the population decline. We posit that the high recruitment rate achieved in 2014-likely due to the maintenance in 2012 of the main nesting sites used by this population-would be sufficient to slow this population's decline if it was sustained each year. Based on the results of diverse pilot studies we conducted, we identified the most likely threats targeting the eggs and immature cohorts, stressing the need to improve reproductive success and survival of immature iguanas. The threats we identified are also involved in the decline of several reptile species, and species from other taxa such as ground-nesting birds. These findings on a little-studied taxon provide further evidence that focusing on the immature life stages of long-lived species can be key to their conservation.
在长寿物种中，尽管成年个体的存活率通常具有最高的弹性，但较不固定的人口统计学参数的时间变化却是种群动态的主要驱动因素。因此，针对补充率采取措施可能是管理这些物种的最有效策略。我们分析了在9年时间里收集的1136份捕获-再捕获记录，这些记录来自极度濒危的小安的列斯鬣蜥的一个孤立种群，我们使用稳健设计的普拉德尔模型来估计成年个体的存活率和补充率。从2013年估计的928只成年个体数量开始，我们发现在8年时间里每年下降4%。正如长寿物种的固定化假说所预期的那样，成年个体的存活率很高且稳定，几乎没有提高的可能性，而补充率随时间变化，很可能是观察到的种群数量下降的原因。然后，我们进行了前瞻性扰动分析，以探究管理该物种的未成年群体是否至少能减缓种群数量的下降。前瞻性扰动分析表明，需要进行重大且持续的保护工作，以实现足够高的补充率来减缓种群数量的下降。我们认为，如果2014年实现的高补充率（可能是由于该种群在2012年对主要筑巢地点的维护）每年都能保持，就足以减缓该种群数量的下降。基于我们开展的各种试点研究结果，我们确定了针对卵和未成年群体的最可能威胁，强调了提高未成年鬣蜥繁殖成功率和存活率的必要性。我们确定的这些威胁也与几种爬行动物物种以及其他类群（如地面筑巢鸟类）的数量下降有关。这些关于一个研究较少的分类群的发现进一步证明，关注长寿物种的未成年生命阶段可能是其保护的关键。
