y research program is inter-disciplinary, combining comparative physiology and ecology with lipid biochemistry and metabolism in vertebrates, and integrates laboratory and field studies on fundamental issues of interest to both medical and zoological communities. My research also has implications for the conservation and management of marine mammals, seabirds and fishes. I am interested in how animals adapt to and exploit their environments and in the physiological and biochemical mechanisms which constrain or provide opportunities for them to do so. In this regard I focus primarily on adaptations related to lipid metabolism in vertebrates.

My long-term goals are
1) to advance understanding of the regulation of lipid metabolism in vertebrates,
2) to apply this and related knowledge to gain a better understanding of the diets of free-ranging animals and the food webs within which they function, and
3) to better understand the physiology of lactation in relation to life history variation.

Although the scope of my work touches upon diverse fields, the present focus of my research is primarily in two complementary areas: first, understanding the role of lipids in the evolution of energetic and reproductive strategies in mammals. Marine mammals, and particularly seals, have been the primary focus of my research because of the critical role that lipid plays in their life histories and especially during lactation and prolonged fasting.

Thus, these species provide excellent models with which to study both fundamental and perhaps limiting aspects of lipid metabolism and lactation, and the interplay and regulation of both. My second focus is on the use of "fatty acid signatures" as a tool to examine the diets and foraging ecology of marine and terrestrial vertebrates. A major thrust of this research over the past three-four years has been to develop the use of fatty acid signatures into a quantitative tool. Although development of this method will continue, it has now reached the point (Iverson et al. in press) where it can be used to help answer previously intractable questions about the foraging ecology of predators.

Studing Seals at Sable Island

• Robert Lewis - Metabolic costs vs. milk production: how fasting grey seal females
  allocate their fatty acid stores
• Bernita Giffin - The effect of fatty acids on growth and survival of clownfish larvae
• Denise Saulnier - Captive validation of fatty acid signature analysis in seabirds
• Matt Logan - Diet specialization and competition among three species of freshwater fish
• Lindsay Smith - Milk fatty acid composition of black bears reflects diet and physiological status
  

• Jacinthe Piche - Ecology and trophic relationships among fishes and invertebrates in the Northwest Hawaiian Islands using fatty acid signatures
  
• Shelley Lang - The influence of parity on milk composition, milk secretory capacity and other aspects of lactation performance in a capital breeding mammal, the grey seal.
• Greg Thiemann - Ecological and demographic factors influencing prey selection and survival in polar bears using quantitative fatty acid signature analysis
• Strahan Tucker - Comparative foraging ecology and diets of free-ranging grey seals, harp seals and hooded seals in the Northwest Atlantic
• Margi Cooper - Lipid metabolism, energetics and quantitative fatty acid signature analysis in juvenile grey seals.
  

• S. Budge, Ph.D. - Assistant Professor, Dalhousie University, Halifax NS
• H. Koopman, Ph.D. - Assistant Professor, University of North Carolina Wilmington.
• C. Beck, Ph.D. Research scientist, Alaska Department of Fish & Game, Anchorage, AK.
• J. Mellish, Ph.D. - Research scientist, Alaska Sea Life Center, Seeward AK.
• D. Coltman, Ph.D. - Assistant Professor in molecular ecology at University of Sheffield, UK
  

Iverson, S. J., Stirling, I. and Lang, S. L. C. in press. Spatial, temporal and individual variation in the diets of polar bears across the Canadian arctic: links with and indicators of changes in prey populations. Symposium of the Zoological Society of London.

Cooper, M. H., Budge, S. M. and Iverson, S. J. 2004. Demonstration of the deposition and modification of dietary fatty acids in pinniped blubber using radiolabelled precursors. Physiological and Biochemical Zoology: in press.

Iverson, S. J., Field, C., Bowen, W. D. and Blanchard, W. 2004. Quantitative fatty acid signature analysis: a new method of estimating predator diets. Ecological Monographs 74: 211-235.

Thiemann, G, W., Budge, S. M. and Iverson, S. J. 2004. Determining blubber fatty acid composition: a comparison of in situ direct and traditional methods. Marine Mammal Science 20: 284-295.

Beck, C. A., Bowen, W. D., McMillan, J. I. and Iverson, S. J. 2003. Sex differences in diving at multiple temporal scales in a size-dimorphic capital breeder. Journal of Animal Ecology 72: 979-993.

Bowen, W. D., Ellis, S. L., Iverson, S. J. and Boness, D. J. 2003. Maternal and newborn life-history traits during periods of contrasting population trends: implications for explaining the decline of harbour seals, Phoca vitulina, on Sable Island. Journal of Zoology London 261: 155-163.

Budge, S. M. and Iverson, S. J. 2003. Quantitative analysis of fatty acid precursors in marine samples: direct conversion of wax ester alcohols and dimethylacetals to fatty acid methyl esters. Journal of Lipid Research 44: 1802-1807.

Koopman, H. N., Iverson, S. J. and Read, A. J. 2003. High concentrations of isovaleric acid in the fats of odontocetes: variation and patterns of accumulation in blubber vs. stability in the melon. Journal of Comparative Physiology 173: 247-261.

Muelbert, M. M. C., Bowen, W. D. and Iverson, S. J. 2003. Weaning mass affects changes in body composition and food intake in harbour seal pups during the first month of independence. Physiological and Biochemical Zoology 76: 418-427.

Budge, S. M., Iverson, S. J., Bowen, W. D. and Ackman, R. G. 2002. Among- and within-species variation in fatty acid signatures of marine fish and invertebrates on the Scotian Shelf, Georges Bank and southern Gulf of St. Lawrence. Canadian Journal of Fisheries and Aquatic Sciences 59: 886-898.

Iverson, S. J., Frost, K. J. and Lang, S. 2002. Fat content and fatty acid composition of forage fish and invertebrates in Prince William Sound, Alaska: factors contributing to among and within species variability. Marine Ecology Progress Series 241: 161-181.

Iverson, S.J., Lang, S. and Cooper, M. 2001. Comparison of the Bligh and Dyer and Folch methods for total lipid determination in a broad range of marine tissue. Lipids 36:1283-1287.

Bowen, W. D., Iverson, S. J., Boness, D. J. and Oftedal, O. T. 2001. Foraging effort, food intake and lactation performance depend on maternal mass in a small phocid seal. Functional Ecology 15: 325-334.

Iverson, S. J., MacDonald, J. and Smith, L. K. 2001. Changes in diet of free-ranging black bears in years of contrasting food availability revealed through milk fatty acids. Canadian Journal of Zoology 79: 2268-2279.

Mellish, J. E. and Iverson, S. J. 2001. Blood metabolites as indicators of nutrient utilization in fasting, lactating phocid seals: does depletion of nutrient reserves terminate lactation? Canadian Journal of Zoology 79: 303-311.

Mellish, J. E., Iverson, S. J. and Bowen, W. D. 2000. Metabolic compensation during high energy output in fasting, lactating grey seals (Halichoerus grypus): metabolic ceilings revisited. Proceedings of the Royal Society, London B 267: 1245-1251.

Links

• Analyzing the Fat of the Sea
• NSERC Steacie Memorial Fellows
• FatLab

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