1. • Quantitative Folch for lipid extraction
• Transesterification to produce fatty acid
methyl esters “FAME” for analysis
MATERIAL AND METHODS
What do Arctic-Invading Killer Whales Eat?
Insight from Blubber Fatty Acid Profile Comparisons of Managed-Care and Wild Orcas
Jessica August*1,Jennifer Bourque*2, Rune Dietz 3, Christian Sonne 3, Aqqalu Rosing 4, Judy St. Leger 5, Melissa McKinney 1,6
*Co-First Authors
1. Department of Natural Resources and the Environment, University of Connecticut, Storrs,CT 06269, United States 2. Department of Environmental Sciences, University of Connecticut, Storrs, CT 06269, United States 3. Arctic Research Centre (ARC), Department of Bioscience, Aarhus University, DK-
4000 Roskilde, Denmark 4. Asvid-Greenland Institute of Natural Resources, DK -3900 Nuuk, Greenland 5. Sea World San Diego, Pathology, San Diego, CA 92109, United States 6. Center for Environmental Sciences and Engineering, University of Connecticut, Storrs, CT 06269, United States
INTRODUCTION
Killer whales (Orcinus orca) are top predators throughout the world’s oceans (Foote et al
2009). Of North Atlantic populations, some killer whales appear to be inhabiting Arctic
waters more frequently and waters further north than in previous decades, apparently
concomitant with declines in sea ice (Ferguson et al 2010). These North Atlantic orcas
are thought to be specialized fish-feeders, but those in the Arctic have been observed
feeding on Arctic and sub-Arctic marine mammals (Higdon et al 2011). Evaluation of their
diets is required to determine the importance of this novel predation on Arctic marine
mammals.
Fatty acid signature analysis can be used to estimate the diets of marine predators
(Budge et al 2006). Fatty acids are used to measure diets as many are taken up relatively
untransformed in predator tissues compared to their diets. Fatty acids are comprised of a
carbon chain, with a methyl terminus (CH3) at one end and a carboxylic acid group at the
other. Shorthand notation for fatty acids is A:Bn-x, where A is the number of carbon
atoms, B is the number of double bonds and x is the position of the first double bond
relative to the terminal methyl group. This shorthand notation will be used throughout
the presentation.
Here, we compared the fatty acid signatures of managed-care orcas to signatures of wild
North Atlantic killer whales recently sampled in Greenlandic Arctic waters. The captive
individuals were fed a strictly fish-based diet, while the stomach contents of some wild
individuals were observed to contain marine mammals. We also evaluated the fatty acid
signatures through the full-depth of the blubber for all individuals to assess how blubber
depth may influence diet assessments of orcas using the fatty acids approach.
Blubber sampling of equal-size
layers through depth (Sample ID:
SW100830)
CONCLUSIONS
● Differences in proportions of 14:1n5, 16:1n7 and 22:6n3 are consistent
with wild whales feeding, at least to some extent, on marine mammals,
relative to the fatty acid signatures reflecting a fish-based diet in the
captive individuals (Herman et al 2005).
● Dietary fatty acid variation with blubber depth suggests that blubber
sampling procedure must be considered in fatty acids-based diet analysis.
● Greater variation in overall fatty acid signatures among wild individuals
suggests inter-individual variation in diets relative to the same diet fed to
all captive individuals. Great variation among wild individuals with blubber
depth could suggest variation in individual diets over time relative to the
constant diet fed to captive individuals.
ACKNOWLEDGEMENTS
Thanks to local hunters for assistance in the wild killer whale sample collection and to
SeaWorld staff for assistance with the managed-care samples. Thanks to Dr. Anthony
Provatas and Gary Ulatowski for allowing us to use instruments in their labs and to Sara
Pedro for assisting in the analysis. Thanks to Rebecca Pugh and John Kucklick (NIST) for
providing the Standard Reference Material. Funding for fatty acids analysis came from a
UConn Scholarship Facilitation grant (M. McKinney) and UConn start-up funds (M.McKinney).
REFERENCES
1. Budge, S. M., Iverson, S. J. and Koopman, H. N. (2006), STUDYING TROPHIC ECOLOGY IN MARINE ECOSYSTEMS USING FATTY ACIDS: A PRIMER ON ANALYSIS AND INTERPRETATION. Marine Mammal Science, 22: 759–801. doi: 10.1111/j.1748-7692.2006.00079. 2. Ferguson, S.H.; Higdon, J.W.; Chmelnitsky, E.G. (2010), The rise of killer whales as a major Arctic predator. In: A little less Arctic: Top predators in the
world's largest northern inland sea, Hudson Bay. P. 117-136. Springer, New York. 3. Foote, A. D., Simila, T., Vikingsson, G. A., Stevick, P. T.. (2009), Movement, site fidelity and connectivity in a top marine predator, the killer whale. Evolutionary Ecology. 24:4: 803-814. doi: 10. 1007/s10682-009093370-x. 4. Herman. D. P., Burrows, D. G., Wade, P. R., Durban, J. W., Matkin, C. O., LeDuc, R. G., Barrett-Lennard, L. G.,
Krahn, M. M. (2005), Feeding ecology of eastern North Pacific killer whales Orcinus orca from fatty acid, stable isotope, and organochlorine analyses of blubber biopsies. Marine Ecology Progress Series. 302: 275-291. 5. Higdon, J. W., Hauser, D. D. W. and Ferguson, S. H. (2012), Killer whales (Orcinus orca) in the Canadian Arctic: Distribution, prey items, group sizes, and seasonality. Marine Mammal Science, 28: E93–
E109. doi: 10.1111/j.1748-7692.2011.00489.x 6. Iverson, S. J., Field, C., Bowen, W. D., & Blanchard, W.. (2004). Quantitative Fatty Acid Signature Analysis: A New Method of Estimating Predator Diets. Ecological Monographs, 74(2), 211–235. Retrieved from http://www.jstor.org/stable/4539054
Sample ID Sample Type Date Sex Age
51601
Wild (East
Greenland)
Unknown Male Adult
51607
Wild (East
Greenland)
15-Jul-2014 Unknown Unknown
51610
Wild (East
Greenland)
20-Jul-2014 Male Unknown
51613
Wild (East
Greenland)
15-Aug-2014 Male Unknown
SW080429 Captive Unknown Female 2.5 years
SW100500 Captive Unknown Female 20 years
SW100830 Captive Unknown Female 25 years
SW100743 Captive Unknown Male 14 years
Table 1. Sample information for wild and captive killer whale
Fig. 2. Blubber layer-specific signatures of dietary fatty
acids in captive samples [upper panel] and wild
samples from Greenland [lower panel] killer whales.
Fig. 1. Comparison of mean (± SE) proportions of 15 major fatty acids in blubber of
captive (grey) and wild Greenland (blue) killer whale samples.
RESULTS
Photo credit: Perkin-Elmer
Gas-chromatography with flame
ionization detection (GC-FID) to
measure fatty acids as mass % of total
● Fatty acid signatures differed between wild and captive individuals. For example,
proportions of 14:1n5 and 16:1n7 were substantially higher in the wild killer whales,
whereas proportions of 22:6n3 were higher in the captive killer whales (Fig. 1)
● Dietary fatty acid proportions varied among layers, decreasing from layer 1 to layer
10 in both captive and wild killer whales (Fig. 2)
● Fatty acid signatures appeared to vary more overall (Fig. 1) and with blubber depth
(Fig. 2) among wild individuals than among captive individuals
Layer 10
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