We learn a huge amount about the humpback whales we study from tiny samples of skin and underlying blubber. We use a specially designed remote biopsy dart system, which we fire from a crossbow, to obtain a tiny sample from each whale we identify in the field.
Each sample measures about 25 mm in length and 5 mm in diameter and weighs only a few grams. In contrast, the whales are about 15 meters long and weigh 40 to 50 tons. The best analogy we can think of is that it’s like a mosquito bite to you or me.
We work hard to ensure that we identify each whale before attempting to sample it. We try to not resample an individual within a field season. We do this by comparing pictures of an animal’s fluke, which is unique to the individual, with our current biopsy/fluke catalog, which is stored on an iPad that we bring onboard. We are able to utilize the pigmentation and scarring of the flukes to identify individuals. If the whale is new to us, we move our Zodiac alongside the whale and fire the biopsy dart at its flank when it arches to dive, usually from a distance of 10 or 15 meters. We are extremely careful throughout the entire sampling process as to not get ahead of the whale or get directly behind its fluke. So far Doug is an excellent driver, and if not for today, I would have a 90% shooting rate, but now am sitting back down around 50%.
The tiny samples provide an enormous amount of information about each whale we sample, including its sex, recent dietary history, reproductive status, and health. We also use genetic markers to infer which breeding population the whale comes from.
Part of my master’s work will be to conduct progesterone assays on the blubber from our samples to determine if female whales are pregnant. We have successfully now documented variations in pregnancy in our samples from 2010, 13, and 14. We are really excited to look at 2015 and this year’s samples over the summer.