DIET AND FORAGING BEHAVIOR OF SEA OTTERS IN SOUTHEAST ALASKA

Abstract Background Reintroducing predators is a promising conservation tool to help remedy human-caused ecosystem changes. However, the growth and spread of a reintroduced population is a spatiotemporal process that is driven by a suite of factors, such as habitat change, human activity, and prey availability. Sea otters (Enhydra lutris) are apex predators of nearshore marine ecosystems that had declined nearly to extinction across much of their range by the early 20th century. In Southeast Alaska, which is comprised of a diverse matrix of nearshore habitat and managed areas, reintroduction of 413 individuals in the late 1960s initiated the growth and spread of a population that now exceeds 25,000. Methods Periodic aerial surveys in the region provide a time series of spatially-explicit data to investigate factors influencing this successful and ongoing recovery. We integrated an ecological diffusion model that accounted for spatially-variable motility and density-dependent population growth, as well as multiple population epicenters, into a Bayesian hierarchical framework to help understand the factors influencing the success of this recovery. Results Our results indicated that sea otters exhibited higher residence time as well as greater equilibrium abundance in Glacier Bay, a protected area, and in areas where there is limited or no commercial fishing. Asymptotic spread rates suggested sea otters colonized Southeast Alaska at rates of 1–8 km/yr with lower rates occurring in areas correlated with higher residence time, which primarily included areas near shore and closed to commercial fishing. Further, we found that the intrinsic growth rate of sea otters may be higher than previous estimates suggested. Conclusions This study shows how predator recolonization can occur from multiple population epicenters. Additionally, our results suggest spatial heterogeneity in the physical environment as well as human activity and management can influence recolonization processes, both in terms of movement (or motility) and density dependence.

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Trends and Carrying Capacity of Sea Otters in Southeast Alaska

Journal of Wildlife Management ◽

10.1002/jwmg.21685 ◽

2019 ◽

Vol 83 (5) ◽

pp. 1073-1089 ◽

Cited By ~ 7

Author(s):

M. Tim Tinker ◽

Verena A. Gill ◽

George G. Esslinger ◽

James Bodkin ◽

Melissa Monk ◽

...

Keyword(s):

Carrying Capacity ◽

Sea Otters ◽

Southeast Alaska

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Temporal patterns in the foraging behavior of sea otters in Alaska

Journal of Wildlife Management ◽

10.1002/jwmg.701 ◽

2014 ◽

Vol 78 (4) ◽

pp. 689-700 ◽

Cited By ~ 12

Author(s):

George G. Esslinger ◽

James L. Bodkin ◽

André R. Breton ◽

Jennifer M. Burns ◽

Daniel H. Monson

Keyword(s):

Foraging Behavior ◽

Temporal Patterns ◽

Sea Otters

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Foraging behavior of adult female Steller sea lions during the breeding season in Southeast Alaska

Marine Mammal Science ◽

10.1111/j.1748-7692.2008.00278.x ◽

2009 ◽

Vol 25 (3) ◽

pp. 588-604 ◽

Cited By ~ 15

Author(s):

M. J. Rehberg ◽

R. D. Andrews ◽

U. G. Swain ◽

D. G. Calkins

Keyword(s):

Foraging Behavior ◽

Breeding Season ◽

Adult Female ◽

Steller Sea Lions ◽

Southeast Alaska ◽

Sea Lions

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Did Tlingit Ancestors Eat Sea Otters? Addressing Intellectual Property and Cultural Heritage through Zooarchaeology

American Antiquity ◽

10.1017/aaq.2019.101 ◽

2020 ◽

Vol 85 (2) ◽

pp. 202-221

Author(s):

Madonna L. Moss

Keyword(s):

Alaska Native ◽

Marine Ecosystem ◽

Keystone Species ◽

Sea Otter ◽

Sea Otters ◽

Southeast Alaska ◽

The North ◽

Commercially Important ◽

The 1960S ◽

The North Pacific

The maritime fur trade caused the extirpation of sea otters from southeast Alaska. In the 1960s, sea otters were reintroduced, and their numbers have increased. Now, sea otters are competing with people for what have become commercially important invertebrates. After having been absent for more than a century, the reentry of this keystone species has unsettled people. Although some communities perceive sea otters as a threat to their livelihoods, others view their return as restoration of the marine ecosystem. The federal Marine Mammal Protection Act authorizes any Alaska Native to harvest sea otters for subsistence provided that the harvest is not wasteful. Some people are seeking to define “traditional” Tlingit use of sea otters as not only using their pelts but consuming them as food, but some Tlingit maintain they never ate sea otters. This project analyzes the largest precontact archaeological assemblage of sea otter bones in southeast Alaska, with the benefit of insights gained from observing a Tlingit hunter skin a sea otter to infer that Tlingit ancestors hunted sea otters primarily for pelts. The extent to which other Indigenous peoples of the North Pacific consumed sea otters as food deserves investigation, especially as sea otters recolonize their historic range.

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Impacts of sea otter (Enhydra lutris) predation on commercially important sea cucumbers (Parastichopus californicus) in southeast Alaska

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2013-0025 ◽

2013 ◽

Vol 70 (10) ◽

pp. 1498-1507 ◽

Cited By ~ 15

Author(s):

Sean D. Larson ◽

Zachary N. Hoyt ◽

Ginny L. Eckert ◽

Verena A. Gill

Keyword(s):

Sea Cucumber ◽

Inverse Relationship ◽

Population Survey ◽

Fishery Management ◽

Sea Otter ◽

Enhydra Lutris ◽

Sea Otters ◽

Sea Cucumbers ◽

Southeast Alaska ◽

Commercially Important

Sea cucumbers (Parastichopus californicus), which are an important commercial, subsistence, and ecological resource, are negatively affected by an expanding sea otter (Enhydra lutris) population in southeast Alaska. A few hundred sea otters were reintroduced into southeast Alaska in the late 1960s after their extirpation during the 18th and 19th century fur trade. In the ensuing decades after recolonization, the sea otter population grew exponentially in number and distribution, and sea cucumbers declined in density in areas with otters, suggesting an inverse relationship between sea otter numbers and sea cucumber density. We evaluated the interaction and effects of sea otters on sea cucumbers using sea otter foraging observations, sea otter population survey data, and sea cucumber density data. Our results indicate that sea cucumber density declined with and without sea otter presence and that the extent of the decline depends on the duration and magnitude of sea otter presence, with 100% decline in areas occupied by sea otters since 1994. Sea otter predation should be included in sea cucumber fishery management as a step toward ecosystem-based management.

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Foraging patterns of California sea otters as indicated by telemetry

Canadian Journal of Zoology ◽

10.1139/z95-060 ◽

1995 ◽

Vol 73 (3) ◽

pp. 523-531 ◽

Cited By ~ 27

Author(s):

Katherine Ralls ◽

Brian B. Hatfield ◽

Donald B. Siniff

Keyword(s):

Foraging Behavior ◽

Prey Size ◽

Prey Type ◽

Dive Duration ◽

Enhydra Lutris ◽

Sea Otters ◽

Foraging Patterns ◽

Radio Transmitters ◽

Males And Females ◽

Juvenile Males

Foraging behavior was studied in 38 sea otters (Enhydra lutris) implanted with radio transmitters. The observed foraging behavior of instrumented individuals was similar to that of uninstrumented otters observed in previous studies: dive duration varied with prey type but not with prey size, dive success was highest for small prey, and the length of surface intervals increased with prey size. However, telemetry revealed that some otters foraged farther offshore and made longer dives than was indicated by visual observations. Individuals within age–sex classes varied in several aspects of foraging behavior, including the duration of dives and length of surface intervals. There were no overall differences between the dive durations or surface intervals during the day and during the night, though some individuals had longer dives or surface intervals during either the day or the night. There were differences in the foraging behavior of the various age–sex classes, the most striking being those between juvenile males and females. Juvenile males foraged much farther offshore [Formula: see text] in deeper water [Formula: see text] than other otters and made long dives during both the day [Formula: see text] and the night [Formula: see text]. Juvenile females fed for longer periods than other otters.

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Diffusion modeling reveals effects of multiple release sites and human activity on a recolonizing apex predator

10.21203/rs.3.rs-341528/v1 ◽

2021 ◽

Author(s):

Joseph Eisaguirre ◽

Perry Williams ◽

Xinyi Lu ◽

Michelle Kissling ◽

William Beatty ◽

...

Keyword(s):

Human Activity ◽

Residence Time ◽

Prey Availability ◽

Commercial Fishing ◽

Apex Predators ◽

Sea Otters ◽

Southeast Alaska ◽

Bayesian Hierarchical ◽

Factors Influencing ◽

Multiple Population

Abstract Background: Reintroducing predators is a promising conservation tool to help remedy human-caused ecosystem changes. However, the growth and spread of a reintroduced population is a spatiotemporal process that is driven by a suite of factors, such as habitat change, human activity, and prey availability. Sea otters (Enhydra lutris) are apex predators of nearshore marine ecosystems that had declined nearly to extinction across much of their range by the early 20th century. In Southeast Alaska, which is comprised of a diverse matrix of nearshore habitat and managed areas, reintroduction of 413 individuals in the late 1960s initiated the growth and spread of a population that now exceeds 25,000. Methods: Periodic aerial surveys in the region provide a time series of spatially-explicit data to investigate factors influencing this successful and ongoing recovery. We integrated an ecological diffusion model that accounted for spatially-variable motility and density-dependent population growth, as well as multiple population epicenters, into a Bayesian hierarchical framework to help understand the factors influencing the success of this recovery. Results: Our results indicated that sea otters exhibited higher residence time as well as greater equilibrium abundance in Glacier Bay, a protected area, and in areas where there is limited or no commercial fishing. Asymptotic spread rates suggested sea otters colonized Southeast Alaska at rates of 1-8 km/yr with lower rates occurring in areas correlated with higher residence time, which primarily included areas near shore and closed to commercial fishing. Further, we found that the intrinsic growth rate of sea otters may be higher than previous estimates suggested. Conclusions: This study shows how predator recolonization can occur from multiple population epicenters. Additionally, our results suggest spatial heterogeneity in the physical environment as well as human activity and management can influence recolonization processes, both in terms of movement (or motility) and density dependence.

Download Full-text