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Morphological identification in skull between spotted seal and harbor seal using geometric morphometrics
Yuichi Arai1, Minoru Kanaiwa2, Mio Kato1,3
1Graduate School of Bioindustry, Tokyo University of Agriculture, Abashiri, Hokkiado, Japan.
Journal of Morphology
|July 31, 2021
Summary
Skull shape differences in spotted seals (Phoca largha) and harbor seals (Phoca vitulina) were identified using geometric morphometrics. Key feeding apparatus landmarks distinguished the species, suggesting varied ecological and reproductive behaviors.
Area of Science:
- Comparative anatomy
- Zoology
- Ecology
Background:
- Skull morphology provides ecological insights, influencing feeding, mating, and migration.
- Spotted seals (Phoca largha) and harbor seals (Phoca vitulina) share similarities but differ in habitat and reproduction.
Purpose of the Study:
- To differentiate skull shapes between spotted and harbor seals using geometric morphometrics.
- To investigate if ecological variations explain observed skull morphological differences.
Main Methods:
- Applied a linear-threshold model to determine skull shape stabilization age.
- Utilized 75 landmarks on 54 adult seals (25 spotted, 29 harbor).
- Employed random forests to identify key landmarks for species identification.
Main Results:
- Skull shape stabilization occurred at 7 years in both species.
- 100% accurate species identification was achieved using eight key landmarks.
- Seven of these landmarks were associated with the feeding apparatus, revealing a broader mouth and mandible in harbor seals compared to spotted seals.
Conclusions:
- Skull morphology, particularly feeding apparatus features, effectively distinguishes spotted and harbor seals.
- Differences in skull shape are likely influenced by both feeding behavior and reproductive strategies, despite both species being dietary generalists and pierce feeders.
