[en] Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in simultaneously fasting and lactating northern elephant seals (Mirounga angustirostris). Stable carbon and nitrogen isotope values were measured in blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. As long- and short-term integrators of diet, blood cells and serum may reflect foraging data or energy reserves from late gestation and lactation, respectively. Limited changes in isotopic signatures of maternal blood over the lactating period were highlighted. Nitrogen isotope fractionation associated with mother-to-offspring transfer of nutrients was generated between mother and offspring during gestation
and lactation. This fractionation was tissue and time-specific, it varied between early and late lactation from +0.6‰ to +1.3‰ in blood cells and from +1.1‰ to nonsignificant value in serum. Therefore, if pups appear to be good proxies to investigate the female trophic ecology especially for C sources, much more caution is required in using δ15N values. Further studies are also needed to better define the relative impact of fasting and lactation on the enrichment or depletion of isotopes in different tissues.
Aurioles, D., P. L. Koch and B. J. Le Boeuf 2006. Differences in foraging location of Mexican and California elephant seals: Evidence from stable isotopes in pups. Marine Mammal Science 22:326-338.
Burns, J. M., S. J. Trumble, M. A. Castellini and J. W. Testa 1998. The diet of Weddell seals in McMurdo Sound, Antarctica as determined from scat collections and stable isotope analysis. Polar Biology 19:272-282.
Burton, R. K., and P. L. Koch 1999. Isotopic tracking of foraging and long-distance migration in northeastern Pacific pinnipeds. Oecologia 119:578-585.
Cherel, Y., K. A. Hobson, F. Bailleul and R. Groscolas 2005. Nutrition, physiology, and stable isotopes: New information from fasting and molting penguins. Ecology 86:2881-2888.
Crocker, D. E., P. M. Webb, D. P. Costa and B. J. Le Boeuf 1998. Protein catabolism and renal function in lactating northern elephant seals. Physiological Zoology 71:485-491.
Crocker, D. E., J. D. Williams, D. P. Costa and B. J. Le Boeuf 2001. Maternal traits and reproductive effort in northern elephant seals. Ecology 82:3541-3555.
Dalerum, F., N. C. Bennett and T. H. Clutton-Brock 2007. Longitudinal differences in 15N between mothers and offspring during and after weaning in a small cooperative mammal, the meerkat (Suricata suricatta). Rapid Communications in Mass Spectrometry 21:1889-1892.
Das, K., G. Lepoint, Y. Leroy and J. M. Bouquegneau 2003. Marine mammals from the southern North Sea: Feeding ecology data from δ13C and δ15N measurements. Marine Ecology Progress Series 263:287-298.
Dauby, P., A. Khomsi and J. M. Bouquegneau 1998. Trophic relationships within intertidal communities of the Brittany Coasts: A stable carbon isotope analysis. Journal of Coastal Research 14:1202-1212.
Davis, T. A., H. V. Nguyen, D. P. Costa and P. J. Reeds 1995. Amino acid composition of pinniped milk. Comparative Biochemistry and Physiology. Part B 110:633-639.
Dehn, L. A., G. G. Sheffield, E. H. Follmann, L. K. Duffy, D. L. Thomas and T. M. O'hara 2007. Feeding ecology of phocid seals and some walrus in the Alaskan and Canadian Arctic as determined by stomach contents and stable isotope analysis. Polar Biology 30:167-181.
Deniro, M. J., and S. Epstein 1978. Influence of diet on the distribution of carbon isotopes in animals. Geochimica et Cosmochimica Acta 42:495-506.
Deniro, M. J., and S. Epstein 1981. Influence of diet on the distribution of nitrogen isotopes in animals. Geochimica et Cosmochimica Acta 45:341-351.
Ducatez, S., S. Dalloyau, P. Richard, C. Guinet and Y. Cherel 2008. Stable isotopes document winter trophic ecology and maternal investment of adult female southern elephant seals (Mirounga leonina) breeding at the Kerguelen Islands. Marine Biology 155:413-420.
Fantle, M. S., A. I. Dittel, S. M. Schwalm, C. E. Epifanio and M. L. Fogel 1999. A food web analysis of the juvenile blue crab, Callinectes sapidus, using stable isotopes in whole animals and individual amino acids. Oecologia 120:416-426.
Fontaine, M. 2002. Sources de variation des concentrations en métaux traces du marsouin commun (Phocoena phocoena) (L.) capturés dans des filets le long des côtes norvégiennes. M.S. dissertation, Université de Liège, Liège, Belgium 64
Fuller, B. T., J. L. Fuller, N. E. Sage, D. A. Harris, T. C. O'Connell and R. E. M. Hedges 2004. Nitrogen balance and δ15N: Why you're not what you eat during pregnancy. Rapid Communications in Mass Spectrometry 18:2889-2896.
Fuller, B. T., J. L. Fuller, N. E. Sage, D. A. Harris, T. C. O'Connell and R. E. M. Hedges 2005. Nitrogen balance and δ15N: Why you're not what you eat during nutritional stress. Rapid Communications in Mass Spectrometry 19:2481-2728.
Gannes, L. Z., C. Martinez Del Rio and P. Koch 1998. Natural abundance variations in stable isotopes and their potential uses in animal physiological ecology. Comparative Biochemistry and Physiology A 119:725-737.
Hilderbrand, G. V., S. D. Farley, C. T. Robbins, T. A. Hanley, K. Titus and C. Servheen 1996. Use of stable isotopes to determine diets of living and extinct bears. Canadian Journal of Zoology 74:2080-2088.
Hobson, K. A., and R. G. Clark 1992a. Assessing avian diets using stable isotopes I: Turnover of carbon-13 in tissues. Condor 94:181-188.
Hobson, K. A., and R. G. Clark 1992b. Assessing avian diets using stable isotopes II: Factors influencing diet-tissue fractionation. Condor 94:189-197.
Hobson, K. A., and R. G. Clark 1993. Turnover of 13C in cellular and plasma fractions of blood: Implications for nondestructive sampling in avian dietary studies. Auk 110:638-641.
Hobson, K. A., and J. L. Sease 1998. Stable isotope analyses of tooth annuli reveal temporal dietary records: An example using Steller sea lions. Marine Mammal Science 14:116-129.
Hobson, K. A., and I. Stirling 1997. Low variation in blood d13C among Hudson Bay polar bears: Implications for metabolism and tracing terrestrial foraging. Marine Mammal Science 13:359-367.
Hobson, K. A., R. T. Alisauska and R. G. Clark 1993. Stable-nitrogen isotope enrichment in avian tissues due to fasting and nutritional stress: Implications for isotopic analyses of diet. Condor 95:388-394.
Hobson, K. A., W. G. J. Ambrose and P. E. Renaud 1995. Sources of primary production, benthic-pelagic coupling, and trophic relationships within the Northeast Water Polynya: Insights from delta13C and delta15N analysis. Marine Ecology Progress Series 128:1-10.
Houser, D. S., and D. E. Crocker 2004. Age, Sex, and reproductive state influence free amino acid concentrations in the fasting elephant seal. Physiological and Biochemical Zoology 77:838-846.
Jenkins, S. G., S. T. Partridge, T. R. Stephenson, S. D. Farley and C. T. Robbins 2001. Nitrogen and carbon isotope fractionation between mothers, neonates, and nursing offspring. Oecologia 129:336-341.
Katzenberg, M. A., and N. C. Lovell 1999. Stable isotope variation in pathological bone. International Journal of Osteoarchaeology 9:316-324.
Kelly, J. F. 2000. Stable isotopes of carbon and nitrogen in the study of avian and mammalian trophic ecology. Canadian Journal of Zoology 78:1-27.
Kovacs, K. M., and D. M. Lavigne 1986. Maternal investment and neonatal growth in phocid seals. Journal of Animal Ecology 55:1035-1051.
Kurle, C. M. 2002. Stable-isotope ratios of blood components from captive northern fur seals (Callorhinus ursinus) and their diet: Applications for studying the foraging ecology of wild otariids. Canadian Journal of Zoology 80:902-909.
Kurle, C. M., and G. A. J. Worthy 2001. Stable isotope assessment of temporal and geographic differences in feeding ecology of northern fur seals (Callorhinus ursinus) and their prey. Oecologia 126:254-265.
Kurle, C. M., and G. A. J. Worthy 2002. Stable nitrogen and carbon isotope ratios in multiple tissues of the northern fur seal Callorhinus ursinus: Implications for dietary and migratory reconstructions. Marine Ecology Progress Series 236:289-300.
Laws, R. M. 1956. The elephant seal (Mirounga leonina Linn.): III. The physiology of reproduction. F. I. D. SURVEY. Scientific Reports 15:1-66.
Le Boeuf, B. J., and R. M. Laws 1994. Elephant seals: An introduction to the genus. Pages 1-26 in B. J. Le Boeuf and R. M. Laws, eds. Elephant seals: Population ecology, behavior, and physiology. University of California Press, Berkeley, CA.
Le Boeuf, B. J., and C. L. Ortiz 1977. Composition of elephant seal milk. Journal of Mammalogy 58:684-685.
Le Boeuf, B. J., R. J. Whiting and R. F. Gantt 1972. Perinatal behavior of northern elephant seal females and their young. Behaviour 43:121-156.
Lesage, V., M. O. Hammill and K. M. Kovacs 2002. Diet-tissue fractionation of stable carbon and nitrogen isotopes in phocid seals. Marine Mammal Science 18:182-193.
McDonald, B. I., and D. E. Crocker 2006. Physiology and behavior influence lactation efficiency in northern elephant seals (Mirounga angustirostris). Physiological and Biochemical Zoology 79:484-496.
Minagawa, M., and E. Wada 1984. Stepwise enrichment of 15N along food chains: Further evidence and the relationship between d15N and animal age. Geochimica et Cosmochimica Acta 50:2143-2146.
Mrosovsky, N., and D. F. Sherry 1980. Animal anorexias. Science of the Total Environment 207:837-842.
Nelson, D. E., A. Angerbjörn, K. Lidén and I. Turk 1998. Stable isotopes and the metabolism of the European cave bear. Oecologia 116:177-181.
Newsome, S. D., P. L. Koch, M. A. Etnier and D. Aurioles-Gamboa 2006. Using carbon and nitrogen isotope values to investigate maternal strategies in northeast Pacific otariids. Marine Mammal Science 22:556-572.
Pearson, S. F., D. J. Levey, C. H. Greenberg and C. M. Del Rio 2003. Effects of elemental composition on the incorporation of dietary nitrogen and carbon isotopic signatures in an omnivorous songbird. Oecologia 135:516-523.
Polischuk, S. C., K. A. Hobson and M. A. Ramsay 2001. Use of stable-carbon and -nitrogen isotopes to assess weaning and fasting in female polar bears and their cubs. Canadian Journal of Zoology 79:499-511.
Rau, G. H., D. G. Ainley, J. L. Bengtson, J. J. Torres and T. L. Hopkins 1992. 15N/14N and 13C/12C in Weddell sea birds, seals and fish: Implications for diet and trophic structure. Marine Ecology Progress Series 84:1-8.
Riedman, M., and C. L. Ortiz 1979. Changes in milk composition during lactation in the northern elephant seal. Physiological Zoology 52:240-249.
Robbins, C. T., L. A. Felicetti and M. Sponheimer 2005. The effect of dietary protein quality on nitrogen isotope discrimination in mammals and birds. Oecologia 144:534-540.
Sare, D. T. J., J. S. Millar and F. J. Longstaffe 2005. Nitrogen- and carbon-isotope fractionation between mothers and offspring in red-backed voles (Clethrionomys gapperi). Canadian Journal of Zoology 83:712-716.
Tieszen, L. L., T. W. Boutton, K. G. Tesdahl and N. A. Slade 1983. Fractionation and turnover of stable carbon isotopes in animal tissues: Implications for 13C analysis of diet. Oecologia 57:32-37.
Voigt, C. C., and F. Matt 2004. Nitrogen stress causes unpredictable enrichments of 15N in two nectar-feeding bat species. Journal of Experimental Biology 207:1741-1748.
Wheater, P. R., B. Young and J. W. Heath 2001. Histologie fonctionnelle. DeBoek Université, Brussels, Belgium.
Zhao, L. 2002. Tracing amino acid metabolism of harbor seals (Phoca vitulina) using stable isotope techniques. Ph.D. thesis, University of Alaska Fairbanks, Fairbanks, AK 433
Zhao, L., D. M. Schell and M. A. Castellini 2006. Dietary macronutrients influence 13C and 15N signatures of pinnipeds: Captive feeding studies with harbor seals (Phoca vitulina). Comparative Biochemistry and Physiology Part A 143:469-478.