ABSTRACT: Birgus latro, the largest terrestrial arthropod in the world, has undergone a substantial decline globally over the last decades, with only a few healthy populations remaining where they are actively protected. We aimed to quantify demographic and spatio-temporal dynamics of a protected population of B. latro on Aldabra Atoll (Seychelles). Based on results along 2 transects on the atoll from 2007 to 2016, we calculated an average (±SE) density of 23.7 ± 1.1 ind. ha^-1. This suggests a population of around 5000 B. latro in the coastal area of Picard Island, which is likely to be an underestimate due to the cryptic nature of the species. The average density within the study area was stable over the study period, and over the yearly cycle, the population exhibited high spatial and temporal variability in count, size and sex ratio and in association with the lunar cycle. Aldabra’s B. latro population is male-biased (3:1 male:female) and sexually dimorphic, with males being larger than females. Males and females moult at different times of the year, and the breeding season overlaps with the region’s wet season (December-March) and was in synchrony with the lunar phase. B. latro on Aldabra present colour polymorphism in a 4:1:1 ratio of orange:blue:intermediate (mixture of orange and blue). Results confirm that Aldabra is an important refuge for B. latro and potentially a natural source population for other areas in the region. Similar long-term studies on B. latro are encouraged to improve knowledge on the species and to support conservation actions to halt the species’ decline.

中文翻译：

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塞舌尔阿尔达布拉环礁上的椰子蟹Birgus latro的种群动态

摘要：近十年来，全球最大的陆生节肢动物天牛（Birgus latro）在全球范围内经历了大幅下降，只有少数健康人群受到积极保护。我们旨在量化阿尔达布拉环礁（塞舌尔）上受保护的油菜芽孢杆菌种群的人口统计和时空动态。根据2007年至2016年环礁上2个样点的结果，我们计算出平均密度（±SE）为23.7±1.1 ind。ha ^-1。这表明大约有5000 B.latro的人口在皮卡德岛（Picard Island）沿海地区，由于该物种的神秘性，这可能被低估了。研究区域内的平均密度在研究期内是稳定的，并且在年度周期内，种群的计数，大小和性别比以及与月球周期相关联表现出高的时空变异性。Aldabra的B. latro人口是男性偏见的（男性：女性：3：1），并且两性具有两性，男性比女性大。雄性和雌性在一年中的不同时间蜕皮，繁殖季节与该地区的雨季重叠（12月至3月），并且与农历相同步。B.latro在Aldabra上，橙色，蓝色：中间（橙色和蓝色的混合物）的比率为4：1：1时呈现颜色多态性。结果证实，亚达伯拉是芽孢杆菌的重要避难所，并且可能是该地区其他地区的自然来源种群。鼓励对油菜双歧杆菌进行类似的长期研究，以提高对该物种的了解，并支持为阻止该物种的衰退而采取的保护行动。