Morphometric and Reproductive Status Data for Sea Otters Collected or Captured in Alaska

Individual otter IDs, collection dates, sampling locations, sex of individual, reproductive status of females and other values were cross-checked and verified with field worksheets. Morphometric data (mass, length, tail length, girth, paw width, canine width, baculum length) were recorded with varying degrees of accuracy. Mass was measured with a 100 lb spring scale periodically checked for accuracy by the Weights and Measures Section of the Alaska Department of Transportation and recoded to the nearest 0.5 lbs and then converted to kg. During experimental harvests (1967-1971), total body length (tip of the nose to the tip of the tail) was measured as curvilinear length along the otter's back as it lay on its stomach, but measured as straight-line length as they lay on their back during early studies (1947-1963) and during more recent studies (1986-2019), and recorded to the nearest 0.1-0.3 cm. Tail lengths were measure using a PVC pipe with a measuring tap glued along its length, which was slid over the tail and pressed firmly up to the base of the tail and recorded to the nearest 0.1-0.3 cm. Paw width was measured using a slide calipers and recorded to the nearest 0.1 cm. Canine width was also measured with a caliper and recorded to the nearest 0.1 mm. Baculum length was measure using a tape measure and feeling the ends of the bone and recorded to the nearest 0.5 cm. All morphometric measures had some amount of measurement error due to soft tissue positioning with curvilinear lengths, baculum lengths, girths, and paw widths the most difficult to measure with precision and accuracy while canine widths were the easiest to measure precisely and accurately. Dependent pup weights were measured with smaller spring scales (20-50 lb) and recorded to the nearest 0.1 lbs then converted kg. Newborn pups and fetuses were weight on ≤ 15-kg capacity balance during early studies (1947-1971). Age was primarily estimated by cementum analysis of a premolar tooth (+/- 1-2 yrs) and/or dental wear patterns. Generally, accuracy of ages estimates decrease with age. Animals aged as dependent pups are considered "known-age" and animals estimated to be >10 yrs are aged with the least amount of certainty.