Nick Kellar

Research Interests:

My research encompasses a range of biological disciplines from reproductive physiology and biochemistry to population biology; however the focus is fairly specific. I measure biomarkers, mostly hormones, from small skin samples of free-ranging cetaceans, to help assess population health, demography, and reproduction.

So why do this? Well first you need to step into the shoes of a field biologist for a moment. Imagine you are on the bow of a research ship, and just a few dozen feet before you are a thousand spotted dolphins, zigging and zagging, leaping and diving. At any given moment, only a fraction of the school is visible from the surface. Each animal comes up just long enough to breathe, then disappears again. Now imagine trying to estimate how many dolphins are in that school let alone, how many are young or old, male or female, pregnant or not pregnant. It seems next to impossible, doesn’t it?

To help us, we employ a darting technique that takes a small piece of skin and blubber called a biopsy. This technique lets us obtain up to fifty biopsies in a single day. Back in the lab, we analyze the levels of steroid hormones in the blubber using laboratory procedures developed here at SWFSC. From this analysis, we can determine if an animal is pregnant, sexually mature, or even if it is likely experiencing chronic stress response. We use these findings to assess the relative health of dolphin and whale populations relative to potential anthropogenic disturbances such a pollution, fishing pressure, and acoustic perturbations from sonar use, shipping traffic, and oil exploration.

Education:

Selected Publications:

• Nicholas M. Kellar, Marisa L. Trego, Susan J. Chivers, Fredrick I. Archer, Jeremiah J. Minich, and Wayne L. Perryman. In Press. Are there biases in biopsy sampling? Potential drivers of sex ratio in projectile biopsy samples from two small delphinids. Marine Mammal Science.
• Kellar, N. M., Trego, M. L., Marks, C. I., Chivers, S. J., Danil, K., and Archer, F. I. (2009). "Blubber testosterone: A potential marker of male reproductive status in short-beaked common dolphins," Marine Mammal Science. 25, 507-522.
• Kellar, N. M., Trego, M. L., Chivers, S. J., and Archer, F. I. (2008). "Histological patterns of dolphin corpus luteum growth and development: finding characters to differentiate CLs ovulation from those of pregnancy " in Marine Biology (Univeristy of California, San Diego, La Jolla), p. 35.
• Kellar, N. M., Trego, M. L., Chivers, S. J., and Archer, F. I. (2008). "Pregnancy patterns of spotted dolphins in the eastern tropical Pacific determined from hormonal analysis of biopsies and their correlation with the pursue-seine tuna fishery " in Marine Biology (University of California, San Diego, La Jolla), p. 186.
• Kellar, N. M., Trego, M. L., Marks, C. I., and Dizon, A. E. (2006). "Determining pregnancy from blubber in three species of delphinids," Marine Mammal Science 22, 1-16.

Additional Information:

Publications

Life History and Blubber Hormones