Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)

Abstract Lactation is the most energetically demanding stage of reproduction in female mammals. Increased energetic allocation toward current reproduction may result in fitness costs, although the mechanisms underlying these trade‐offs are not well understood. Trade‐offs during lactation may include...

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Main Authors: Sarah M. Chinn, Daniel H. Monson, M. Tim Tinker, Michelle M. Staedler, Daniel E. Crocker
Format: Article
Language:English
Published: Wiley 2018-08-01
Series:Ecology and Evolution
Subjects:
Online Access:https://doi.org/10.1002/ece3.4280
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spelling doaj-dbfb1cde043a4e548ba8e62f4323d1c82021-03-02T07:49:10ZengWileyEcology and Evolution2045-77582018-08-018168433844710.1002/ece3.4280Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)Sarah M. Chinn0Daniel H. Monson1M. Tim Tinker2Michelle M. Staedler3Daniel E. Crocker4Department of Biology Sonoma State University Rohnert Park CaliforniaU.S. Geological Survey Alaska Science Center Anchorage AlaskaU.S. Geological Survey Western Ecological Research Center Long Marine Laboratory Santa Cruz CaliforniaMonterey Bay Aquarium Monterey CaliforniaDepartment of Biology Sonoma State University Rohnert Park CaliforniaAbstract Lactation is the most energetically demanding stage of reproduction in female mammals. Increased energetic allocation toward current reproduction may result in fitness costs, although the mechanisms underlying these trade‐offs are not well understood. Trade‐offs during lactation may include reduced energetic allocation to cellular maintenance, immune response, and survival and may be influenced by resource limitation. As the smallest marine mammal, sea otters (Enhydra lutris) have the highest mass‐specific metabolic rate necessitating substantial energetic requirements for survival. To provide the increased energy needed for lactation, female sea otters significantly increase foraging effort, especially during late‐lactation. Caloric insufficiency during lactation is reflected in the high numbers of maternal deaths due to End‐Lactation Syndrome in the California subpopulation. We investigated the effects of lactation and resource limitation on maternal stress responses, metabolic regulation, immune function, and antioxidant capacity in two subspecies of wild sea otters (northern: E. l. nereis and southern: E. l. kenyoni) within the California, Washington, and Alaska subpopulations. Lactation and resource limitation were associated with reduced glucocorticoid responses to acute capture stress. Corticosterone release was lower in lactating otters. Cortisol release was lower under resource limitation and suppression during lactation was only evident under resource limitation. Lactation and resource limitation were associated with alterations in thyroid hormones. Immune responses and total antioxidant capacity were not reduced by lactation or resource limitation. Southern sea otters exhibited higher concentrations of antioxidants, immunoglobulins, and thyroid hormones than northern sea otters. These data provide evidence for allocation trade‐offs during reproduction and in response to nutrient limitation but suggest self‐maintenance of immune function and antioxidant defenses despite energetic constraints. Income‐breeding strategists may be especially vulnerable to the consequences of stress and modulation of thyroid function when food resources are insufficient to support successful reproduction and may come at a cost to survival, and thereby influence population trends.https://doi.org/10.1002/ece3.4280lactationresource limitationsea ottertrade‐offs
collection DOAJ
language English
format Article
sources DOAJ
author Sarah M. Chinn
Daniel H. Monson
M. Tim Tinker
Michelle M. Staedler
Daniel E. Crocker
spellingShingle Sarah M. Chinn
Daniel H. Monson
M. Tim Tinker
Michelle M. Staedler
Daniel E. Crocker
Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)
Ecology and Evolution
lactation
resource limitation
sea otter
trade‐offs
author_facet Sarah M. Chinn
Daniel H. Monson
M. Tim Tinker
Michelle M. Staedler
Daniel E. Crocker
author_sort Sarah M. Chinn
title Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)
title_short Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)
title_full Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)
title_fullStr Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)
title_full_unstemmed Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)
title_sort lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (enhydra lutris)
publisher Wiley
series Ecology and Evolution
issn 2045-7758
publishDate 2018-08-01
description Abstract Lactation is the most energetically demanding stage of reproduction in female mammals. Increased energetic allocation toward current reproduction may result in fitness costs, although the mechanisms underlying these trade‐offs are not well understood. Trade‐offs during lactation may include reduced energetic allocation to cellular maintenance, immune response, and survival and may be influenced by resource limitation. As the smallest marine mammal, sea otters (Enhydra lutris) have the highest mass‐specific metabolic rate necessitating substantial energetic requirements for survival. To provide the increased energy needed for lactation, female sea otters significantly increase foraging effort, especially during late‐lactation. Caloric insufficiency during lactation is reflected in the high numbers of maternal deaths due to End‐Lactation Syndrome in the California subpopulation. We investigated the effects of lactation and resource limitation on maternal stress responses, metabolic regulation, immune function, and antioxidant capacity in two subspecies of wild sea otters (northern: E. l. nereis and southern: E. l. kenyoni) within the California, Washington, and Alaska subpopulations. Lactation and resource limitation were associated with reduced glucocorticoid responses to acute capture stress. Corticosterone release was lower in lactating otters. Cortisol release was lower under resource limitation and suppression during lactation was only evident under resource limitation. Lactation and resource limitation were associated with alterations in thyroid hormones. Immune responses and total antioxidant capacity were not reduced by lactation or resource limitation. Southern sea otters exhibited higher concentrations of antioxidants, immunoglobulins, and thyroid hormones than northern sea otters. These data provide evidence for allocation trade‐offs during reproduction and in response to nutrient limitation but suggest self‐maintenance of immune function and antioxidant defenses despite energetic constraints. Income‐breeding strategists may be especially vulnerable to the consequences of stress and modulation of thyroid function when food resources are insufficient to support successful reproduction and may come at a cost to survival, and thereby influence population trends.
topic lactation
resource limitation
sea otter
trade‐offs
url https://doi.org/10.1002/ece3.4280
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