Numbers of walruses selected for measurement-based aging and resolution of age classifications from hold sequences recorded in 2011.

aProportions in parenthesis are relative to 1,413 attempted measurements.
bProportions in parenthesis are relative to the column totals given in the 1st row.
1Column only includes larger animals where aging required tusk and snout measurements.
2An attempt was made to find a measurable image but none with the requisite perfectly perpendicular front or side view was found, and only a visual estimate of age was made or age was classified as unknown.
3Column only includes smaller animals where aging did not require tusk or snout measurements.

a 括号内的占比以1413次尝试测量为基准计算。
b 括号内的占比以第一行给出的列总计值为基准计算。
1 该列仅包含需通过象牙与吻部测量完成年龄判定的大型动物。
2 研究人员曾尝试寻找可用于测量的图像，但未找到符合要求的完全垂直正面或侧面视角的图像，因此仅能通过视觉估算年龄，或判定年龄为未知。
3 该列仅包含无需通过象牙与吻部测量即可完成年龄判定的小型动物。