Environmental impacts on reproductive responses of Pacific walruses (Odobenus rosmarus divergens) and subsistence users of St. Lawrence Island
Dissertation (Ph.D.) University of Alaska Fairbanks, 2020 An interdisciplinary approach is used in understanding change and resiliency in St. Lawrence Island (SLI) resources and resource users throughout this dissertation. Historically SLI inhabitants have relied on the Pacific walrus (Odobenus rosm...
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ftunivalaska:oai:scholarworks.alaska.edu:11122/12307 2023-05-15T15:43:41+02:00 Environmental impacts on reproductive responses of Pacific walruses (Odobenus rosmarus divergens) and subsistence users of St. Lawrence Island Larsen Tempel, Jenell T. Atkinson, Shannon Kruse, Gordon H. Fugate, Corey Pyenson, Nick 2020-08 http://hdl.handle.net/11122/12307 en_US eng http://hdl.handle.net/11122/12307 Department of Fisheries Reproduction Walrus Environmental effects Bering Sea Climate Hunting Alaska Saint Lawrence Island Endocrine Subsistence hunting Doctor of Philosophy in Fisheries Dissertation phd 2020 ftunivalaska 2023-02-23T21:37:53Z Dissertation (Ph.D.) University of Alaska Fairbanks, 2020 An interdisciplinary approach is used in understanding change and resiliency in St. Lawrence Island (SLI) resources and resource users throughout this dissertation. Historically SLI inhabitants have relied on the Pacific walrus (Odobenus rosmarus divergens) for their survival and this resource is still highly valued for cultural and dietary purposes. The responses of Pacific walruses and SLI subsistence users to environmental change was analyzed. In walruses, reproductive capacity was analyzed using an anatomical approach as well as reproductive plasticity which was determined using a physiological approach to characterize their estrus cycle. A suite of anatomical measurements were developed to characterize reproductive capacity of walruses by analyzing ovaries from three distinct time frames during a 35-year period. Reproductive capacity was reduced during time frames when carrying capacity (K) was reached and when large environmental changes occurred in the Bering Sea, including years of very low sea ice extent. Reproductive capacity was high in times when K was lower and harvest levels were greater. Our results explained how perturbations in K and environmental changes may have influenced reproductive capacity of the population in the past. Endocrine techniques were used in ovarian tissues to determine if progesterone and total estrogens are useful indicators of female reproductive status in walruses harvested during the spring hunt. Progesterone and total estrogen concentrations were greater in the reproductive tissues of unbred and pregnant females than postpartum females, however neither hormone could distinguish between pregnant and unbred animals. These results provide the first physiological evidence for pseudopregnancy in this species, rather than a postpartum estrus. Lastly, discussions were held with SLI community members to determine changes in key subsistence resources and community resiliency with regard to food security. Walruses ranked ... Doctoral or Postdoctoral Thesis Bering Sea Odobenus rosmarus Sea ice St Lawrence Island Alaska walrus* University of Alaska: ScholarWorks@UA Bering Sea Fairbanks Lawrence Island ENVELOPE(-103.718,-103.718,56.967,56.967) Pacific |
institution |
Open Polar |
collection |
University of Alaska: ScholarWorks@UA |
op_collection_id |
ftunivalaska |
language |
English |
topic |
Reproduction Walrus Environmental effects Bering Sea Climate Hunting Alaska Saint Lawrence Island Endocrine Subsistence hunting Doctor of Philosophy in Fisheries |
spellingShingle |
Reproduction Walrus Environmental effects Bering Sea Climate Hunting Alaska Saint Lawrence Island Endocrine Subsistence hunting Doctor of Philosophy in Fisheries Larsen Tempel, Jenell T. Environmental impacts on reproductive responses of Pacific walruses (Odobenus rosmarus divergens) and subsistence users of St. Lawrence Island |
topic_facet |
Reproduction Walrus Environmental effects Bering Sea Climate Hunting Alaska Saint Lawrence Island Endocrine Subsistence hunting Doctor of Philosophy in Fisheries |
description |
Dissertation (Ph.D.) University of Alaska Fairbanks, 2020 An interdisciplinary approach is used in understanding change and resiliency in St. Lawrence Island (SLI) resources and resource users throughout this dissertation. Historically SLI inhabitants have relied on the Pacific walrus (Odobenus rosmarus divergens) for their survival and this resource is still highly valued for cultural and dietary purposes. The responses of Pacific walruses and SLI subsistence users to environmental change was analyzed. In walruses, reproductive capacity was analyzed using an anatomical approach as well as reproductive plasticity which was determined using a physiological approach to characterize their estrus cycle. A suite of anatomical measurements were developed to characterize reproductive capacity of walruses by analyzing ovaries from three distinct time frames during a 35-year period. Reproductive capacity was reduced during time frames when carrying capacity (K) was reached and when large environmental changes occurred in the Bering Sea, including years of very low sea ice extent. Reproductive capacity was high in times when K was lower and harvest levels were greater. Our results explained how perturbations in K and environmental changes may have influenced reproductive capacity of the population in the past. Endocrine techniques were used in ovarian tissues to determine if progesterone and total estrogens are useful indicators of female reproductive status in walruses harvested during the spring hunt. Progesterone and total estrogen concentrations were greater in the reproductive tissues of unbred and pregnant females than postpartum females, however neither hormone could distinguish between pregnant and unbred animals. These results provide the first physiological evidence for pseudopregnancy in this species, rather than a postpartum estrus. Lastly, discussions were held with SLI community members to determine changes in key subsistence resources and community resiliency with regard to food security. Walruses ranked ... |
author2 |
Atkinson, Shannon Kruse, Gordon H. Fugate, Corey Pyenson, Nick |
format |
Doctoral or Postdoctoral Thesis |
author |
Larsen Tempel, Jenell T. |
author_facet |
Larsen Tempel, Jenell T. |
author_sort |
Larsen Tempel, Jenell T. |
title |
Environmental impacts on reproductive responses of Pacific walruses (Odobenus rosmarus divergens) and subsistence users of St. Lawrence Island |
title_short |
Environmental impacts on reproductive responses of Pacific walruses (Odobenus rosmarus divergens) and subsistence users of St. Lawrence Island |
title_full |
Environmental impacts on reproductive responses of Pacific walruses (Odobenus rosmarus divergens) and subsistence users of St. Lawrence Island |
title_fullStr |
Environmental impacts on reproductive responses of Pacific walruses (Odobenus rosmarus divergens) and subsistence users of St. Lawrence Island |
title_full_unstemmed |
Environmental impacts on reproductive responses of Pacific walruses (Odobenus rosmarus divergens) and subsistence users of St. Lawrence Island |
title_sort |
environmental impacts on reproductive responses of pacific walruses (odobenus rosmarus divergens) and subsistence users of st. lawrence island |
publishDate |
2020 |
url |
http://hdl.handle.net/11122/12307 |
long_lat |
ENVELOPE(-103.718,-103.718,56.967,56.967) |
geographic |
Bering Sea Fairbanks Lawrence Island Pacific |
geographic_facet |
Bering Sea Fairbanks Lawrence Island Pacific |
genre |
Bering Sea Odobenus rosmarus Sea ice St Lawrence Island Alaska walrus* |
genre_facet |
Bering Sea Odobenus rosmarus Sea ice St Lawrence Island Alaska walrus* |
op_relation |
http://hdl.handle.net/11122/12307 Department of Fisheries |
_version_ |
1766377880738070528 |