Elephant Seal Sightings, Macquarie Island

At Macquarie Island 1000 seals were weighed per annum between 1993-2003 at birth and individually marked with two plastic flipper tags in the inter-digital webbing of their hind flippers. These tagged seals were weighed again at weaning, when length, girth, fat depth, and flipper measurements were made. Three weeks after weaning 2000 seals were permanently and individually marked by hot-iron branding. Recaptures and re-weigings of these known aged individuals were used to calculate growth and age-specific survival of the seals. Similar data were collected from elephant seals between 1950 and 1965 when seals were individually marked by hot-iron branding. Mark-recapture data from these cohorts were used to assess the demography of the declining population. Length and mass data were also collected for these cohorts and were used, for the first time, to assess the growth of individual seals without killing them.

1993年至2003年间，研究人员在麦夸里岛（Macquarie Island）每年对1000只海豹开展出生体重测量，并通过在后肢趾间蹼佩戴两枚塑料鳍肢标记环（flipper tag）的方式完成个体标记。上述带标记的海豹会在断奶期再次接受体重测量，同时记录其体长、胸围、脂肪厚度及鳍肢尺寸。断奶三周后，研究人员会通过热铁烙印法（hot-iron branding）为2000只海豹施加永久性个体标记。后续通过对这些已知年龄个体的重捕与再次称重，研究人员得以计算海豹的生长情况及年龄特异性存活率。1950年至1965年间，研究人员同样从象海豹群体中收集了类似数据集，彼时研究人员通过热铁烙印法完成海豹的个体标记。基于这些同期群的标记重捕数据，研究者得以评估该衰退种群的种群统计学特征。此外，研究人员还为这些同期群收集了体长与体重数据，首次实现了无需处死个体即可评估单只海豹生长状况的研究。