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Maniscalco JM. Changes in the overwintering diet of Steller sea lions (Eumetopias jubatus) in relation to the 2014 – 2016 northeast Pacific marine heatwave. Glob Ecol Conserv 2023. [DOI: 10.1016/j.gecco.2023.e02427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023] Open
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2
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John JS, Thometz NM, Boerner K, Denum L, Kendall TL, Richter BP, Gaspard JC, Williams TM. Metabolic trade-offs in tropical and subtropical marine mammals: unique maintenance and locomotion costs in West Indian manatees and Hawaiian monk seals. J Exp Biol 2021; 224:271210. [PMID: 34357378 PMCID: PMC8353161 DOI: 10.1242/jeb.237628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 06/09/2021] [Indexed: 11/20/2022]
Abstract
Unlike the majority of marine mammal species, Hawaiian monk seals (Neomonachus schauinslandi) and West Indian manatees (Trichechus manatus latirostris) reside exclusively in tropical or subtropical waters. Although potentially providing an energetic benefit through reduced maintenance and thermal costs, little is known about the cascading effects that may alter energy expenditure during activity, dive responses and overall energy budgets for these warm-water species. To examine this, we used open-flow respirometry to measure the energy expended during resting and swimming in both species. We found that the average resting metabolic rates (RMRs) for both the adult monk seal (753.8±26.1 kJ h-1, mean±s.e.m.) and manatees (887.7±19.5 kJ h-1) were lower than predicted for cold-water marine mammal species of similar body mass. Despite these relatively low RMRs, both total cost per stroke and total cost of transport (COTTOT) during submerged swimming were similar to predictions for comparably sized marine mammals (adult monk seal: cost per stroke=5.0±0.2 J kg-1 stroke-1, COTTOT=1.7±0.1 J kg-1 m-1; manatees: cost per stroke=2.0±0.4 J kg-1 stroke-1, COTTOT=0.87±0.17 J kg-1 m-1). These lower maintenance costs result in less variability in adjustable metabolic costs that occur during submergence for warm-water species. However, these reduced maintenance costs do not appear to confer an advantage in overall energetic costs during activity, potentially limiting the capacity of warm-water species to respond to anthropogenic or environmental threats that require increased energy expenditure.
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Affiliation(s)
- Jason S John
- University of California Santa Cruz, Coastal Biology Building, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Nicole M Thometz
- University of California Santa Cruz, Coastal Biology Building, 130 McAllister Way, Santa Cruz, CA 95060, USA.,University of San Francisco, 2130 Fulton Street, San Francisco, CA 94117, USA
| | - Katharine Boerner
- Mote Marine Laboratory & Aquarium, 1600 Ken Thompson Pkwy, Sarasota, FL 34236, USA
| | - Laura Denum
- Mote Marine Laboratory & Aquarium, 1600 Ken Thompson Pkwy, Sarasota, FL 34236, USA
| | - Traci L Kendall
- University of California Santa Cruz, Coastal Biology Building, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Beau P Richter
- University of California Santa Cruz, Coastal Biology Building, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Joseph C Gaspard
- Pittsburgh Zoo & PPG Aquarium, One Wild Place, Pittsburgh, PA 15206, USA
| | - Terrie M Williams
- University of California Santa Cruz, Coastal Biology Building, 130 McAllister Way, Santa Cruz, CA 95060, USA
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Milling CR, Rachlow JL, Chappell MA, Camp MJ, Johnson TR, Shipley LA, Paul DR, Forbey JS. Seasonal temperature acclimatization in a semi-fossorial mammal and the role of burrows as thermal refuges. PeerJ 2018; 6:e4511. [PMID: 29576977 PMCID: PMC5858582 DOI: 10.7717/peerj.4511] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 02/26/2018] [Indexed: 01/08/2023] Open
Abstract
Small mammals in habitats with strong seasonal variation in the thermal environment often exhibit physiological and behavioral adaptations for coping with thermal extremes and reducing thermoregulatory costs. Burrows are especially important for providing thermal refuge when above-ground temperatures require high regulatory costs (e.g., water or energy) or exceed the physiological tolerances of an organism. Our objective was to explore the role of burrows as thermal refuges for a small endotherm, the pygmy rabbit (Brachylagus idahoensis), during the summer and winter by quantifying energetic costs associated with resting above and below ground. We used indirect calorimetry to determine the relationship between energy expenditure and ambient temperature over a range of temperatures that pygmy rabbits experience in their natural habitat. We also measured the temperature of above- and below-ground rest sites used by pygmy rabbits in eastern Idaho, USA, during summer and winter and estimated the seasonal thermoregulatory costs of resting in the two microsites. Although pygmy rabbits demonstrated seasonal physiological acclimatization, the burrow was an important thermal refuge, especially in winter. Thermoregulatory costs were lower inside the burrow than in above-ground rest sites for more than 50% of the winter season. In contrast, thermal heterogeneity provided by above-ground rest sites during summer reduced the role of burrows as a thermal refuge during all but the hottest periods of the afternoon. Our findings contribute to an understanding of the ecology of small mammals in seasonal environments and demonstrate the importance of burrows as thermal refuge for pygmy rabbits.
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Affiliation(s)
- Charlotte R Milling
- Department of Fish and Wildlife Sciences, University of Idaho, Moscow, ID, USA.,School of Environment and Natural Resources, Ohio State University, Columbus, OH, USA
| | - Janet L Rachlow
- Department of Fish and Wildlife Sciences, University of Idaho, Moscow, ID, USA
| | - Mark A Chappell
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, USA
| | - Meghan J Camp
- School of the Environment, Washington State University, Pullman, WA, USA
| | - Timothy R Johnson
- Department of Statistical Science, University of Idaho, Moscow, ID, USA
| | - Lisa A Shipley
- School of the Environment, Washington State University, Pullman, WA, USA
| | - David R Paul
- Department of Movement Sciences, University of Idaho, Moscow, ID, USA
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Diaz Gomez M, Rosen DA, Trites AW. Net energy gained by northern fur seals (Callorhinus ursinus) is impacted more by diet quality than by diet diversity. CAN J ZOOL 2016. [DOI: 10.1139/cjz-2015-0143] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Understanding whether northern fur seals (Callorhinus ursinus (L., 1758)) are negatively affected by changes in prey quality or diversity could provide insights into their on-going population decline in the central Bering Sea. We investigated how six captive female fur seals assimilated energy from eight different diets consisting of four prey species (walleye pollock (Gadus chalcogrammus Pallas, 1814, formerly Theragra chalcogrammus (Pallas, 1814)), Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847), capelin (Mallotus villosus (Müller, 1776)), and magister armhook squid (Berryteuthis magister (Berry, 1913))) fed alone or in combination. Net energy was quantified by measuring fecal energy loss, urinary energy loss, and heat increment of feeding. Digestible energy (95.9%–96.7%) was high (reflecting low fecal energy loss) and was negatively affected by ingested mass and dietary protein content. Urinary energy loss (9.3%–26.7%) increased significantly for high-protein diets. Heat increment of feeding (4.3%–12.4%) was significantly lower for high-lipid diets. Overall, net energy gain (57.9%–83.0%) was affected by lipid content and varied significantly across diets. Mixed-species diets did not provide any energetic benefit over single-species diets. Our study demonstrates that diet quality was more important in terms of energy gain than diet diversity. These findings suggest that fur seals consuming low-quality prey in the Bering Sea would be more challenged to obtain sufficient energy to satisfy energetic and metabolic demands, independent of high prey abundance.
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Affiliation(s)
- Mariana Diaz Gomez
- Department of Zoology and Marine Mammal Research Unit, Institute for the Oceans and Fisheries, Room 247, 2202 Main Mall, AERL, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Department of Zoology and Marine Mammal Research Unit, Institute for the Oceans and Fisheries, Room 247, 2202 Main Mall, AERL, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - David A.S. Rosen
- Department of Zoology and Marine Mammal Research Unit, Institute for the Oceans and Fisheries, Room 247, 2202 Main Mall, AERL, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Department of Zoology and Marine Mammal Research Unit, Institute for the Oceans and Fisheries, Room 247, 2202 Main Mall, AERL, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Andrew W. Trites
- Department of Zoology and Marine Mammal Research Unit, Institute for the Oceans and Fisheries, Room 247, 2202 Main Mall, AERL, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Department of Zoology and Marine Mammal Research Unit, Institute for the Oceans and Fisheries, Room 247, 2202 Main Mall, AERL, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Hoopes LA, Rea LD, Christ A, Worthy GAJ. No evidence of metabolic depression in Western Alaskan juvenile Steller sea lions (Eumetopias jubatus). PLoS One 2014; 9:e85339. [PMID: 24416394 PMCID: PMC3887069 DOI: 10.1371/journal.pone.0085339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 12/03/2013] [Indexed: 11/18/2022] Open
Abstract
Steller sea lion (Eumetopias jubatus) populations have undergone precipitous declines through their western Alaskan range over the last four decades with the leading hypothesis to explain this decline centering around changing prey quality, quantity, or availability for this species (i.e., nutritional stress hypothesis). Under chronic conditions of reduced food intake sea lions would conserve energy by limiting energy expenditures through lowering of metabolic rate known as metabolic depression. To examine the potential for nutritional stress, resting metabolic rate (RMR) and body composition were measured in free-ranging juvenile Steller sea lions (N = 91) at three distinct geographical locations (Southeast Alaska, Prince William Sound, Central Aleutian Islands) using open-flow respirometry and deuterium isotope dilution, respectively. Average sea lion RMR ranged from 6.7 to 36.2 MJ d(-1) and was influenced by body mass, total body lipid, and to a lesser extent, ambient air temperature and age. Sea lion pups captured in the Aleutian Islands (region of decline) had significantly greater body mass and total body lipid stores when compared to pups from Prince William Sound (region of decline) and Southeast Alaska (stable region). Along with evidence of robust body condition in Aleutian Island pups, no definitive differences were detected in RMR between sea lions sampled between eastern and western populations that could not be accounted for by higher percent total body lipid content, suggesting that that at the time of this study, Steller sea lions were not experiencing metabolic depression in the locations studied.
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Affiliation(s)
- Lisa A. Hoopes
- Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Lorrie D. Rea
- Alaska Department of Fish and Game, Division of Wildlife Conservation, Anchorage, Alaska, United States of America
| | - Aaron Christ
- Alaska Department of Fish and Game, Division of Wildlife Conservation, Anchorage, Alaska, United States of America
| | - Graham A. J. Worthy
- Department of Biology, University of Central Florida, Orlando, Florida, United States of America
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Gerlinsky CD, Trites AW, Rosen DAS. Steller sea lions (Eumetopias jubatus) have greater blood volumes, higher diving metabolic rates and a longer aerobic dive limit when nutritionally stressed. ACTA ACUST UNITED AC 2013; 217:769-78. [PMID: 24198263 DOI: 10.1242/jeb.089599] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Marine mammal foraging behaviour inherently depends on diving ability. Declining populations of Steller sea lions may be facing nutritional stress that could affect their diving ability through changes in body composition or metabolism. Our objective was to determine whether nutritional stress (restricted food intake resulting in a 10% decrease in body mass) altered the calculated aerobic dive limit (cADL) of four captive sea lions diving in the open ocean, and how this related to changes in observed dive behaviour. We measured diving metabolic rate (DMR), blood O2 stores, body composition and dive behaviour prior to and while under nutritional restriction. We found that nutritionally stressed sea lions increased the duration of their single long dives, and the proportion of time they spent at the surface during a cycle of four dives. Nutritionally stressed sea lions lost both lipid and lean mass, resulting in potentially lower muscle O2 stores. However, total body O2 stores increased due to rises in blood O2 stores associated with having higher blood volumes. Nutritionally stressed sea lions also had higher mass-specific metabolic rates. The greater rise in O2 stores relative to the increase in mass-specific DMR resulted in the sea lions having a longer cADL when nutritionally stressed. We conclude that there was no negative effect of nutritional stress on the diving ability of sea lions. However, nutritional stress did lower foraging efficiency and require more foraging time to meet energy requirements due to increases in diving metabolic rates and surface recovery times.
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Affiliation(s)
- Carling D Gerlinsky
- Marine Mammal Research Unit, Fisheries Center and Department of Zoology, University of British Columbia, 2204 Main Mall, Vancouver, British Columbia, Canada, V6T 1Z4
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Young BL, Rosen DAS, Haulena M, Hindle AG, Trites AW. Environment and feeding change the ability of heart rate to predict metabolism in resting Steller sea lions (Eumetopias jubatus). J Comp Physiol B 2010; 181:105-16. [DOI: 10.1007/s00360-010-0504-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 07/21/2010] [Accepted: 07/23/2010] [Indexed: 10/19/2022]
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Richmond JP, Jeanniard du Dot T, Rosen DAS, Zinn SA. Seasonal influence on the response of the somatotropic axis to nutrient restriction and re-alimentation in captive Steller sea lions (Eumetopias jubatus). JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL GENETICS AND PHYSIOLOGY 2010; 313:144-56. [PMID: 20084663 DOI: 10.1002/jez.584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Fluctuations in availability of prey resources can impede acquisition of sufficient energy for maintenance and growth. By investigating the hormonal mechanisms of the somatotropic axis that link nutrition, fat metabolism, and lean tissue accretion, we can assess the physiological impact of decreased nutrient intake on growth. Further, species that undergo seasonal periods of reduced intake as a part of their normal life history may have a differential seasonal response to nutrient restriction. This experiment evaluated the influence of season and age on the response of the somatotropic axis, including growth hormone (GH), insulin-like growth factor (IGF)-I, and IGF-binding proteins (BP), to reduced nutrient intake and re-alimentation in Steller sea lions. Eight captive females (five juveniles, three sub-adults) were subject to 28-day periods of food restriction, controlled re-feeding, and ad libitum recovery in summer (long-day photoperiod) and winter (short-day photoperiod). Hormone concentrations were insensitive to type of fish fed (low fat pollock vs. high fat herring), but sensitive to energy intake. Body mass, fat, and IGF-I declined, whereas GH and IGFBP-2 increased during feed restriction. Reduced IGF-I and IGFBP with increased GH during controlled re-feeding suggest that animals did not reach positive energy balance until fed ad libitum. Increased IGF-I, IGFBP-2, IGFBP-3, and reduced GH observed in summer reflected seasonal differences in energy partitioning. There was a strong season and age effect in the response to restriction and re-alimentation, indicating that older, larger animals are better able to cope with stress associated with energy deficit, regardless of season.
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Affiliation(s)
- Julie P Richmond
- Department of Animal Science, University of Connecticut, Storrs, Connecticut, CT06269, USA.
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Jeanniard du Dot T, Rosen DAS, Trites AW. Energy reallocation during and after periods of nutritional stress in Steller sea lions: low-quality diet reduces capacity for physiological adjustments. Physiol Biochem Zool 2009; 82:516-30. [PMID: 19637969 DOI: 10.1086/603637] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Two groups of female Steller sea lions (groups H and P) were subjected to periods of energy restriction and subsequent refeeding during winter and summer to determine changes in energy partitioning among principal physiological functions and the potential consequences to their fitness. Both sea lion groups consumed high-quality fish (herring) before and after the energy restrictions. During restrictions, group H was fed a lower quantity of herring and group P a caloric equivalent of low-quality fish (pollock). Quantitative estimates of maintenance and production energies and qualitative estimates of thermoregulation, activity, and basal metabolic rate were measured. During summer, all animals compensated for the imposed energy deficit by releasing stored energy (production energy). Group H also optimized the energy allocation to seasonal conditions by increasing activity during summer, when fish are naturally abundant (foraging effort), and by decreasing thermoregulation capacity when waters are warmer. During winter, both groups decreased the energy allocated to overall maintenance functions (basal metabolic rate, thermoregulation, and activity together) in addition to releasing stored energy, but they preserved thermoregulatory capacity. Group H also decreased activity levels in winter, when foraging in the wild is less efficient, unlike group P. Overall, sea lions fed pollock did not change energy allocation to suit environmental conditions as readily as those fed herring. This implies that a low energy-density diet may further reduce fitness of animals in the wild during periods of nutritional stress.
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Affiliation(s)
- Tiphaine Jeanniard du Dot
- Department of Zoology and Marine Mammal Research Unit, Fisheries Center, University of British Columbia, 2202 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada.
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Noren DP, Rea LD, Loughlin TR. A model to predict fasting capacities and utilization of body energy stores in weaned Steller sea lions (Eumetopias jubatus) during periods of reduced prey availability. CAN J ZOOL 2009. [DOI: 10.1139/z09-074] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The population decline of Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) may be linked to a decline in juvenile survivorship. Limitations in prey availability may contribute to the decline, thus it is important to understand fasting capacities of Steller sea lions. For most mammals, fat catabolism is the preferred energetic pathway to ensure that protein is spared. However, marine mammals also have a conflicting requirement to conserve fat because the main site of fat storage is the blubber layer, which is also their primary thermal barrier when at sea. We developed a dynamic state variable model to demonstrate how protein and fat reserve utilization and maximum fasting duration are influenced by body condition and time spent foraging. This model was parameterized with respect to conditions faced by juvenile and subadult Steller sea lions foraging unsuccessfully during a period of reduced prey availability. The model accurately predicted changes in fat and protein mass of juvenile and subadult Steller sea lions fasting in captivity. Furthermore, the model demonstrated that body lipid content, body mass, and the proportion of time spent in water influence energy reserve catabolism and maximum fasting durations. Consequently, small, lean individuals are particularly susceptible to reductions in prey availability.
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Affiliation(s)
- D. P. Noren
- National Marine Mammal Laboratory, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Center, 7600 Sand Point Way Northeast, Seattle, WA 98115, USA
- National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, WA 98112, USA
- Department of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816, USA
- Alaska Department of Fish and Game, Division of Wildlife Conservation, Marine Mammal Research Section, 245 O’Neill Building, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - L. D. Rea
- National Marine Mammal Laboratory, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Center, 7600 Sand Point Way Northeast, Seattle, WA 98115, USA
- National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, WA 98112, USA
- Department of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816, USA
- Alaska Department of Fish and Game, Division of Wildlife Conservation, Marine Mammal Research Section, 245 O’Neill Building, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - T. R. Loughlin
- National Marine Mammal Laboratory, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Center, 7600 Sand Point Way Northeast, Seattle, WA 98115, USA
- National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, WA 98112, USA
- Department of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816, USA
- Alaska Department of Fish and Game, Division of Wildlife Conservation, Marine Mammal Research Section, 245 O’Neill Building, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
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ROSEN DAVIDAS. Steller sea lions
Eumetopias jubatus
and nutritional stress: evidence from captive studies. Mamm Rev 2009. [DOI: 10.1111/j.1365-2907.2009.00150.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- DAVID A. S. ROSEN
- Marine Mammal Research Unit, University of British Columbia, 2202 Main Mall, Vancouver, BC, V6T 1Z4, Canada
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12
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Zhao Z, Wang D. Plasticity in the Physiological Energetics of Mongolian Gerbils Is Associated with Diet Quality. Physiol Biochem Zool 2009; 82:504-15. [DOI: 10.1086/603630] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Bozinovic F, Rojas JM, Broitman BR, Vásquez RA. Basal metabolism is correlated with habitat productivity among populations of degus (Octodon degus). Comp Biochem Physiol A Mol Integr Physiol 2009; 152:560-4. [PMID: 19162212 DOI: 10.1016/j.cbpa.2008.12.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 12/22/2008] [Accepted: 12/31/2008] [Indexed: 10/21/2022]
Abstract
Several competing hypotheses attempt to explain how environmental conditions affect mass-independent basal metabolic rate (BMR) in mammals. One of the most inclusive is the hypothesis that associates BMR with food habits, including habitat productivity. The effects of food habits have been widely investigated at the interspecific level, and variation between individuals and populations has been largely ignored. Intraspecific analysis of physiological traits has the potential to compensate for many pitfalls associated with interspecific analyses and serve as a useful approach for evaluating hypotheses regarding metabolic adaptation. Here we tested the effects of climatic variables (mean annual rainfall=PP, mean annual temperature=T(A)), net primary productivity (NPP) and the de Martonne index (DMi) of aridity on mass-independent BMR among four populations of the caviomorph rodent Octodon degus along a geographic gradient in Chile. BMR was measured on animals maintained in a common garden acclimation set-up, thus kept under the same environment and diet quality for at least 6 months. Mass-independent BMR was significantly different among degu populations showing a large intraspecific spread in metabolic rates. A very large fraction of interpopulational variability in mass-independent BMR was explained by NPP, PP and DMi. Our results were conclusive about the effects of habitat productivity on setting the level of mass-independent BMR at the intraspecific-interpopulational level.
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Affiliation(s)
- Francisco Bozinovic
- Center for Advanced Studies in Ecology and Biodiversity, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile.
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Bozinovic F, Muñoz JLP, Cruz-Neto AP. Intraspecific Variability in the Basal Metabolic Rate: Testing the Food Habits Hypothesis. Physiol Biochem Zool 2007; 80:452-60. [PMID: 17508340 DOI: 10.1086/518376] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/05/2007] [Indexed: 11/03/2022]
Abstract
Several competing hypotheses attempt to explain how environmental conditions affect mass-independent basal metabolic rate (BMR) in mammals. One of the most inclusive and yet debatable hypotheses is the one that associates BMR with food habits, including habitat productivity. These effects have been widely investigated at the interspecific level under the assumption that for any given species all traits are fixed. Consequently, the variation among individuals is largely ignored. Intraspecific analysis of physiological traits has the potential to compensate for many of the pitfalls associated with interspecific analyses and, thus, to be a useful approach for evaluating hypotheses regarding metabolic adaptation. In this study, we investigated the effects of food quality, availability, and predictability on the BMR of the leaf-eared mouse Phyllotis darwini. BMR was measured on freshly caught animals from the field, since they experience natural seasonal variations in environmental factors (and, hence, variations in habitat productivity) and diet quality. BMR was significantly correlated with the proportion of dietary plants and seeds. In addition, BMR was significantly correlated with monthly habitat productivity. Path analysis indicated that, in our study, habitat productivity was responsible for the observed changes in BMR, while diet per se had no effect on this variable.
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Affiliation(s)
- Francisco Bozinovic
- Center for Advanced Studies in Ecology and Biodiversity and Departamento de Ecologia, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Santiago 6513677, Chile.
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15
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Kumagai S, Rosen DAS, Trites AW. Body mass and composition responses to short-term low energy intake are seasonally dependent in Steller sea lions (Eumetopias jubatus). J Comp Physiol B 2006; 176:589-98. [PMID: 16625362 DOI: 10.1007/s00360-006-0082-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2004] [Revised: 03/21/2006] [Accepted: 03/29/2006] [Indexed: 10/24/2022]
Abstract
Steller sea lions (Eumetopias jubatus) were fed restricted iso-caloric amounts of Pacific herring (Clupea pallasi) or walleye pollock (Theragra chalcogramma) for 8-9 days, four times over the course of a year to investigate effects of season and prey composition on sea lion physiology. At these levels, the sea lions lost body mass at a significantly higher rate during winter (1.6 +/- 0.14 kg day(-1)), and at a lower rate during summer (1.2 +/- 0.32 kg day(-1)). Decreases in body fat mass and standard metabolic rates during the trials were similar throughout the seasons and for both diet types. The majority of the body mass that was lost when eating pollock derived from decreases in lipid mass, while a greater proportion of the mass lost when eating herring derived from decreases in lean tissue, except in the summer when the pattern was reversed. Metabolic depression was not observed during all trials despite the constant loss of body mass. Our study supports the hypothesis that restricted energy intake may be more critical to Steller sea lions in the winter months, and that the type of prey consumed (e.g., herring or pollock) may have seasonally specific effects on body mass and composition.
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Affiliation(s)
- Saeko Kumagai
- Marine Mammal Research Unit, University of British Columbia, 2202 Main Mall, Vancouver, BC, Canada
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16
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Rosen DAS, Trites AW. Examining the potential for nutritional stress in young Steller sea lions: physiological effects of prey composition. J Comp Physiol B 2005; 175:265-73. [PMID: 15900507 DOI: 10.1007/s00360-005-0481-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Revised: 01/31/2005] [Accepted: 02/24/2005] [Indexed: 11/28/2022]
Abstract
The effects of high- and low-lipid prey on the body mass, body condition, and metabolic rates of young captive Steller sea lions (Eumetopias jubatus) were examined to better understand how changes in prey composition might impact the physiology and health of wild sea lions and contribute to their population decline. Results of three feeding experiments suggest that prey lipid content did not significantly affect body mass or relative body condition (lipid mass as a percent of total mass) when sea lions could consume sufficient prey to meet their energy needs. However, when energy intake was insufficient to meet daily requirements, sea lions lost more lipid mass (9.16+/-1.80 kg+/-SE) consuming low-lipid prey compared with eating high-lipid prey (6.52+/-1.65 kg). Similarly, the sea lions lost 2.7+/-0.9 kg of lipid mass while consuming oil-supplemented pollock at maintenance energy levels but gained 5.2+/-2.7 kg lipid mass while consuming identical energetic levels of herring. Contrary to expectations, there was a 9.7+/-1.8% increase in metabolism during mass loss on submaintenance diets. Relative body condition decreased only 3.7+/-3.8% during periods of imposed nutritional stress, despite a 10.4+/-4.8% decrease in body mass. These findings raise questions regarding the efficacy of measures of relative body condition to detect such changes in nutritional status among wild animals. The results of these three experiments suggest that prey composition can have additional effects on sea lion energy stores beyond the direct effects of insufficient energy intake.
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Affiliation(s)
- David A S Rosen
- Marine Mammal Research Unit, University of British Columbia, 6248 Biological Sciences Road, Vancouver, BC, Canada, V6T 1Z4.
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MCMAHON CLIVER, BESTER MARTHANN, BURTON HARRYR, HINDELL MARKA, BRADSHAW COREYJA. Population status, trends and a re-examination of the hypotheses explaining the recent declines of the southern elephant seal Mirounga leonina. Mamm Rev 2005. [DOI: 10.1111/j.1365-2907.2005.00055.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Cruz-Neto AP, Bozinovic F. The Relationship between Diet Quality and Basal Metabolic Rate in Endotherms: Insights from Intraspecific Analysis. Physiol Biochem Zool 2004; 77:877-89. [PMID: 15674763 DOI: 10.1086/425187] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2004] [Indexed: 11/03/2022]
Abstract
In this article, we review intraspecific studies of basal metabolic rate (BMR) that address the correlation between diet quality and BMR. The "food-habit hypothesis" stands as one of the most striking and often-mentioned interspecific patterns to emerge from studies of endothermic energetics. Our main emphasis is the explicit empirical comparison of predictions derived from interspecific studies with data gathered from within-species studies in order to explore the mechanisms and functional significance of the putative adaptive responses encapsulated by the food-habit hypothesis. We suggest that, in addition to concentrating on the relationship among diet quality, internal morphology, and BMR, new studies should also attempt to unravel alternative mechanisms that shape the interaction between diet and BMR, such as enzymatic plasticity, and the use of energy-saving mechanisms, such as torpor. Another avenue for future study is the measurement of the effects of diet quality on other components of the energy budget, such as maximum thermogenic and sustainable metabolic rates. It is possible that the effects of diet quality operate on such components rather than directly on BMR, which might then push or pull along changes in these traits. Results from intraspecific studies suggest that the factors responsible for the association between diet and BMR at an ecological timescale might not be the same as those that promoted the evolution of this correlation. Further analyses should consider how much of a role the proximate and ultimate processes have played in the evolution of BMR.
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Affiliation(s)
- Ariovaldo P Cruz-Neto
- Departamento de Zoologia, Instituto de Biociências, Universidade Estadual Paulista, Caixa Postal 199 13506-900, Rio Claro, São Paulo, Brazil.
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Silva SI, Jaksic FM, Bozinovic F. Interplay between metabolic rate and diet quality in the South American fox, Pseudalopex culpaeus. Comp Biochem Physiol A Mol Integr Physiol 2004; 137:33-8. [PMID: 14720588 DOI: 10.1016/j.cbpb.2003.09.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We studied the metabolic costs associated with the ingestion of peppertree fruits (Schinus molle) in the culpeo fox, Pseudalopex culpaeus, the second largest canid in South America. Throughout its range of distribution, this fox feeds on rodents and other small vertebrates, and also on peppertree fruits, which represent 98% of total fruits consumed in semiarid Chile. Peppertree contains a high diversity of phytochemicals. Foxes feeding on diets containing rats and peppertree fruits (mixed diets) exhibited a 98.9% increase in basal rate of metabolism when compared to rat-acclimated foxes. Thus, acute ingestion of chemically defended fruits has an energetic cost for the fox, reflected in higher values of basal metabolism. Increased metabolic rates may be associated with increased protein synthesis for detoxification and for tissue repair, including the production of biotransformation enzymes.
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Affiliation(s)
- Sergio I Silva
- Center for Advanced Studies in Ecology and Biodiversity and Departamento de Ecología, Pontificia Universidad Católica de Chile, P.O. Box 114-D, Santiago, Chile.
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TRITES AW, DONNELLY CP. The decline of Steller sea lionsEumetopias jubatusin Alaska: a review of the nutritional stress hypothesis. Mamm Rev 2003. [DOI: 10.1046/j.1365-2907.2003.00009.x] [Citation(s) in RCA: 234] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Boyle R, Dearing MD. Ingestion of juniper foliage reduces metabolic rates in woodrat (Neotoma) herbivores. ZOOLOGY 2003; 106:151-8. [PMID: 16351900 DOI: 10.1078/0944-2006-00109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2003] [Revised: 05/05/2003] [Accepted: 05/29/2003] [Indexed: 11/18/2022]
Abstract
Ingestion of plant secondary compounds by herbivores is predicted to increase resting or basal metabolic rates. We tested this hypothesis with two species of woodrat herbivores, Neotoma stephensi and Neotoma albigula, consuming diets of juniper (Juniperus monosperma), which is rich in plant secondary compounds. In nature, N. stephensi specializes on juniper, whereas N. albigula consumes a variety of plant species including juniper. We measured resting metabolic rates (RMR) of woodrats on control, 25% juniper and a treatment containing the maximum tolerable dose of juniper (50% juniper for N. albigula and 70% juniper for N. stephensi). Ingestion of a juniper diet resulted in decreased RMR in both species of woodrats. We propose several potential mechanisms for metabolic depression of Neotoma on juniper diets. Our novel results underscore the need for more studies utilizing plant-based diets to determine the general effect of plant secondary compounds on metabolic rates of herbivores.
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Affiliation(s)
- Rebecca Boyle
- Tasmanian School of Pharmacy, University of Tasmania, Hobart, Australia
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Rosen DAS, Trites AW. Changes in metabolism in response to fasting and food restriction in the Steller sea lion (Eumetopias jubatus). Comp Biochem Physiol B Biochem Mol Biol 2002; 132:389-99. [PMID: 12031465 DOI: 10.1016/s1096-4959(02)00048-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Many animals lower their resting metabolism (metabolic depression) when fasting or consuming inadequate food. We sought to document this response by subjecting five Steller sea lions to periods of: (1) complete fasting; or (2) restricting them to 50% of their normal herring diet. The sea lions lost an average of 1.5% of their initial body mass per day (2.30 kg/d) during the 9-14-day fast, and their resting metabolic rates decreased 31%, which is typical of a "fasting response". However, metabolic depression did not occur during the 28-day food restriction trials, despite the loss of 0.30% of body mass per day (0.42 kg/d). This difference in response suggests that undernutrition caused by reduced food intake may stimulate a "hunger response", which in turn might lead to increased foraging effort. The progressive changes in metabolism we observed during the fasts were related to, but were not directly caused by, changes in body mass from control levels. Combining these results with data collected from experiments when Steller sea lions were losing mass on low energy squid and pollock diets reveals a strong relationship between relative changes in body mass and relative changes in resting metabolism across experimental conditions. While metabolic depression caused by fasting or consuming large amounts of low energy food reduced the direct costs from resting metabolism, it was insufficient to completely overcome the incurred energy deficit.
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Affiliation(s)
- David A S Rosen
- Marine Mammal Research Unit, Fisheries Centre, University of British Columbia, 6248 Biological Sciences Rd., Vancouver, B.C. V6T 1Z4, Canada.
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Abstract
We tested the hypothesis that animals that reduce their body mass in response to decreased photoperiod do not develop diet-induced obesity (DIO) when fed a high-fat diet (HFD). Bank voles (Clethrionomys glareolus) fed a diet with fat content of 13.5% by mass and 28.2% by energy, for 5 weeks, did not develop hyperphagia and were resistant to DIO, consistent with predictions. There was no significant difference between food (g/day) or energy intake (kJ/day) between the experimental or control group (fed a standard diet with fat content of 5.4% by mass and 12.3% by energy) over the duration of the experiment. However, as a result of a higher apparent energy assimilation efficiency (AEAE), voles fed the HFD assimilated significantly more energy over the 5-week period. Furthermore, they consumed twice as much fat per day as controls. There were no significant differences in resting metabolic rate (RMR) over time or between groups over the 5-week period. In conclusion, bank voles achieved resistance to DIO despite assimilating more energy than control animals fed the standard diet and taking in twice as much fat. Resistance did not occur by modification of RMR, implicating differences in activity levels.
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Affiliation(s)
- W L Peacock
- Aberdeen Centre for Energy Regulation and Obesity (ACERO), Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ Scotland, UK.
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Veloso C, Bozinovic F. Interplay between acclimation time and diet quality on basal metabolic rate in females of degus Octodon degus (Rodentia: Octodontidae). J Zool (1987) 2000. [DOI: 10.1111/j.1469-7998.2000.tb01235.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Rosen DAS, Trites AW. Pollock and the decline of Steller sea lions: testing the junk-food hypothesis. CAN J ZOOL 2000. [DOI: 10.1139/z00-060] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The decline of Steller sea lions (Eumetopias jubatus) in the Gulf of Alaska and the Aleutian Islands may be the result of them eating too much pollock (a gadid fish) instead of a more balanced and diverse diet containing fattier fishes, such as herring or sandlance. We sought to test this junk-food hypothesis by feeding six captive Steller sea lions (ages 0.9-4.5 years) only pollock or herring. All sea lions gained mass while eating herring. However, eating only pollock for short periods (11-23 d) caused the study animals to lose an average of 6.5% of their initial body mass (0.6 kg/d) over an average feeding trial of 16 d (initial mass averaged 125 kg). The animals were allowed to eat as much pollock as they wanted but did not increase their food intake to compensate for the low energy they were receiving. The sea lions showed progressive metabolic depression while losing body mass on a pollock-only diet. The loss of body mass while eating pollock was due to the lower gross energy content of pollock versus herring, the higher cost of digesting pollock, and the increased energy loss from digesting the larger quantity of fish needed to compensate for the lower energy content of pollock. Thus, our sea lions would have had to eat 35-80% more pollock than herring to maintain similar net energy intakes. Results from our captive-feeding studies are consistent with the junk-food hypothesis and have serious implications for Steller sea lions that have been eating primarily pollock in the Gulf of Alaska and the Aleutian Islands.
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