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，研究人员每年在麦夸里岛（Macquarie Island）对1000头海豹于出生时开展体重测量，并通过在后肢趾间蹼处佩戴两枚塑料鳍肢标签（plastic flipper tags）完成个体标记。上述佩戴标记的海豹会在断奶时再次接受体重测量，同时同步采集其体长、胸围、脂肪厚度及鳍肢尺寸等相关数据。断奶三周后，研究人员采用热铁烙印法（hot-iron branding）对2000头海豹实施永久性个体标记。后续通过对这些已知年龄个体的重捕与再次称重，计算该种群海豹的生长动态与年龄特异性存活率。 1950年至1965年间，研究人员针对象海豹（elephant seals）收集了同类研究数据，当时通过热铁烙印法完成个体标记。基于这些同生群（cohort）的标记重捕数据，研究人员对该衰退种群的种群统计学特征展开评估。此外，研究人员还采集了这些同生群的体长与体重数据，并首次在不猎杀海豹的前提下，利用这些数据评估个体海豹的生长情况。