Determining sex of adult Pacific walruses from mandible measurements

Pacific walruses (Odobenus rosmarus divergens) play a vital role in Arctic marine ecosystems and the subsistence lifestyle of Alaska Native communities. Museum collections contain numerous archaeological and historic walrus specimens that have proven useful in a variety of studies; however, for many cases, the sex of these specimens is unknown. Sexes of adult (> 5 years determined by tooth aging) Atlantic walruses (Odobenus rosmarus rosmarus) have been accurately determined in previous studies using mandible measurements. We tested the validity of this approach for Pacific walruses, and used full fusion of the mandibular symphysis to define adults. Using high precision digital calipers (± 0.01 mm), four measurements were taken either on the left or right side of 91 walrus mandibles: 80 modern mandibles (70 known-sex specimens; 10 unknown-sex specimens) and 11 archaeological mandibles of unknown sex. We used linear discriminant function analysis (LDFA) to determine what measurements best distinguished Pacific walrus males from females. Minimum mandible thickness had the most predictive power, whereas mandible length, height, and depth, were less predictive. Posterior probabilities indicated that LDFA classified the known-sex Pacific walruses with 100% accuracy, and unknown sex with ≥ 90% probability. The ability to define the sex of unknown individuals accurately could greatly increase the sample size of future projects dealing with skeletal remains, and will improve future research efforts.

• Publication year

  2020

• Venue

  Journal of Mammalogy

• Publication date

  2020-06-20

• Fields of study

  Biology, Medicine, Environmental Science

• Identifiers
  DOI 10.1093/jmammal/gyaa051PMID 33033468PMCID 7528639
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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