The killer whale (Orcinus orca) is the top marine predator and perhaps the most widespread vertebrate on earth, occurring in all the world’s oceans. They prey on protected marine mammal populations and commercially important fish stocks, and we need to understand the impacts of this predation, particularly in rapidly changing ecosystems. We are therefore undertaking a multi-faceted, but integrated, research program to study killer whales in a number of different locations (Pitman 2011).
Currently recognized as a single species, our recent genetic investigations have suggested that there may be multiple species of killer whales (Morin et al. 2010). Notably, our research has revealed that there are at least 4 distinct forms of killer whales in Antarctic and Southern Ocean waters (Pitman and Ensor 2003; Pitman et al. 2010), with distinct genetic differences (LeDuc et al. 2008; Foote et al. 2011) and morphological differences (Pitman et al. 2007a; see poster).
Abundance estimation is a key component for assessing ecosystem impact of killer whale predation. We are compiling photographic identification catalogues of individual killer whales in different systems (e.g. Alaska, Antarctica, California coast[), and fitting statistical capture-recapture models to estimate abundance and population dynamics (e.g. Ford et al. 2007; Durban et al. 2010; Matkin et al. in press).
Identification photographs are used to produce photographic “capture-recapture” estimates of abundance
Small skin and blubber biopsies are collected from free-ranging whales using floating darts fired from a crossbow.
Direct observation of predation (e.g., Pitman et al., 2001, 2003, 2007b; Pitman and Dutton, 2004; Pitman and Durban, 2010, 2011) are required to evaluate the diet and prey requirements of killer whales. However, observations are limited and we also employ biochemical methods for inferring diet and assessing nutritional status. These include chemical analyses of skin and blubber biopsies to infer dietary preferences (Krahn et al. 2008), and photogrammetry for assessing size, energetic requirements and body condition (Fearnbach et al. 2011).
The impact of killer whale predation on local prey populations will be mediated by their movements. We deploy small (49g) satellite tags on killer whales to provide higher resolution and longer term monitoring of their movement patterns. This approach is being used to study the migration patterns of Antarctic killer whales (Andrews et al., 2008; Durban and Pitman, 2011), the movement patterns of killer whales hunting migratory gray whales off the west coast of the United States, and to locate whales in real time to observe predation behavior (Pitman and Durban, 2011).
Andrews, R. D., Pitman, R. L., Ballance, L. T. 2008 Satellite tracking reveals distinct movement patterns for Type B and Type C killer whales in the southern Ross Sea, Antarctica. Polar Biology 31:1461-1468.
Durban, J., Ellifrit, D., Dahlheim, M., Waite, J., Matkin, C., Barrett-Lennard, L., Ellis, G., Pitman, R., LeDuc, R., Wade, P. 2010 Photographic mark-recapture analysis of clustered mammal-eating killer whales around the Aleutian Islands and Gulf of Alaska. Marine Biology. 1-14.
Durban, J.W., Pitman, R.L. 2011. Antarctic killer whales make rapid, round-trip movements to subtropical waters: evidence for physiological maintenance migrations? Biology Letters. doi:10.1098 / rsbl.2011.0875.
Durban, J., Deecke, V. 2011. How do we study killer whales? Journal of the American Cetacean Society, 40: 6-14.
Fearnbach, H., Durban, J. W., Ellifrit, D. K., Balcomb, K. C. I. 2011 Size and long-term growth trends of Endangered fish-eating killer whales. Endangered Species Research. 13, 173-180.
Foote, A. D., Morin, P. A., Durban, J. W., Pitman, R. L., Wade, P., Willerslev, E., Gilbert, M. T. P., da Fonseca, R. R. 2011 Positive selection on the killer whale mitogenome. Biology Letters. 7, 116.
Ford, J.K.B., G.M. Ellis, and J.W. Durban. 2007. An Assessment of the Potential for Recovery of West Coast Transient Killer whales Using Coastal Waters of British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2007/088. http://www.dfo-mpo.gc.ca/csas/Csas/ Publications/ResDocs-DocRech/2007/2007_088_e.htm.
Krahn, M., Pitman, R., Burrows, D., Herman, D., Pearce, R. 2008 Use of chemical tracers to assess diet and persistent organic pollutants in Antarctic Type C killer whales. Marine Mammal Science. 24, 643-663.
LeDuc, R., Robertson, K., Pitman, R. 2008 Mitochondrial sequence divergence among Antarctic killer whale ecotypes is consistent with multiple species. Biology Letters. 4, 426.
Matkin, C., Durban, J. 2011. Killer whales in Alaskan waters. Journal of the American Cetacean Society, 40: 24-29.
Matkin C, Durban J, Andrews R, Straley J, Ellis G, Matkin D. In Press. Contrasting abundance and residency patterns of two sympatric populations of transient killer whales in the northern Gulf of Alaska. Fisheries Bulletin.
Morin, P., Archer, F., Foote, A., Vilstrup, J., Allen, E., Wade, P., Durban, J., Parsons, K., Pitman, R., Li, L. 2010 Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome research. 20, 908.
Pitman, R. L., Ensor, P. 2003 Three forms of killer whales (Orcinus orca) in Antarctic waters. Journal of Cetecean Research and Management. 5, 131-139.
Pitman, R. L., Ballance, L. T., Mesnick, S. I., Chivers, S. J. 2001 Killer whale predation on sperm whales: observations and implications. Marine Mammal Science. 17, 494-507.
Pitman, R.L., S. O’Sullivan, and B. Mase. 2003. Killer whales (Orcinus orca) attack a school of pantropical spotted dolphins (Stenella attenuata) in the Gulf of Mexico. Aquatic Mammals 29(3):321-324.
Pitman, R., Dutton, P. 2004 Killer whale predation on a leatherback turtle in the northeast Pacific. Pacific Science. 58, 497-498.
Pitman, R., Perryman, W., LeRoi, D., Eilers, E. 2007 A dwarf form of killer whale in Antarctica. Journal of Mammalogy. 88, 43-48.
Pitman, R., Fearnbach, H., Leduc, R., Gilpatrick, J., Ford, J., Ballance, L. 2007 Killer whales preying on a blue whale calf on the Costa Rica Dome: genetics, morphometrics, vocalisations and composition of the group. Journal of Cetacean Research and Management. 9, 151.
Pitman, R. L., Durban, J. W. 2010 Killer whale predation on penguins in Antarctica. Polar Biology. 33, 1589-1594. (10.1007/s00300-010-0853-5)
Pitman, R. L., Durban, J. W., Greenfelder, M., Guinet, C., Jorgensen, M., Olson, P. A., Plana, J., Tixier, P., Towers, J. R. 2010 Observations of a distinctive morphotype of killer whale (Orcinus orca), type D, from subantarctic waters. Polar Biology. 34, 303-306.
Pitman, R. L., Durban, J. W. 2011 Cooperative hunting behavior, prey selectivity and prey handling by pack ice killer whales (Orcinus orca), type B, in Antarctic Peninsula waters. Marine Mammal Science. (DOI: 10.1111/j.1748-7692.2010.00453.x)
Pitman, R. L. (ed.). 2011. Killer whale: the top, top predator. Whalewatcher (Journal of the American Cetacean Society) 40(1):1-67.