Forecasting sea otter recolonization: Insights from isotopic analysis of modern and zooarchaeological populations

Proceedings of the Royal Society B, Biological Sciences
By: , and 

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Abstract

Retrospective datasets offer essential context for conservation by revealing species’ ecological roles before industrial-era human impacts. We analysed isotopic compositions of pre-industrial and modern sea otters (Enhydra lutris) to reconstruct pre-extirpation ecology and offer insights for management. Our study focuses on southeast Alaska (SEAK), where sea otters are recolonizing, and northern Oregon, where translocations are being considered. We measured bulk bone collagen δ13C and δ15N values and essential amino acid δ13C values of extirpated sea otters from archaeological contexts, and bulk isotopic values from vibrissae of modern SEAK sea otters. We compare these results with published isotopic data of potential prey and additional archaeological datasets. In SEAK, our data show pre-industrial sea otter populations consumed infaunal bivalves and used soft-sediment (33%) and kelp forest habitats (67%), with sub-regional variation. We anticipate current populations will expand into this historical niche, and conflict with regional traditional/subsistence bivalve fisheries will persist. In northern Oregon, isotopic data from extirpated sea otters indicate past consumption of low trophic level invertebrates and a stronger reliance on kelp forests (88%) rather than soft-sediment habitats, highlighting the importance of kelp forests for future translocations. Our work exemplifies the value of historical ecology in informing conservation strategies for recovering species.

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Publication type Article
Publication Subtype Journal Article
Title Forecasting sea otter recolonization: Insights from isotopic analysis of modern and zooarchaeological populations
Series title Proceedings of the Royal Society B, Biological Sciences
DOI 10.1098/rspb.2024.1682
Volume 292
Issue 2039
Year Published 2025
Language English
Publisher The Royal Society
Contributing office(s) Alaska Science Center Ecosystems
Description 20241682, 12 p.
Country United States
State Alaska, Oregon
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