Sleuthing the Secret Lives of Killer Whales with DNA
The Killer Whale Adoption Program has supported leading edge DNA-based research on killer whales since the 1992. In that year, Dr. Lance Barrett-Lennard (then a Vancouver Aquarium Research Associate and PhD student) and long-time killer whale researcher Graeme Ellis began working on a system for obtaining biopsies (small samples of tissue) from cetaceans in the wild, to obtain DNA for Lance’s PhD research. It seemed to them that skin would be the easiest tissue to obtain. Fortunately, cetacean skin contains lots of DNA, and a piece smaller than a pea provides enough DNA for dozens of tests and analyses. Several researchers in other parts of the world were using crossbow bolts (arrows) fitted with round punches at the end to collect skin from blue, humpback and other large whales, but no one had come up with a system specifically for killer whales.
Figuring It Out
Lance and Graeme’s first priority was to minimize pain and disturbance to the whales, so they talked to animal trainers and vets about their experiences with killer whales. All agreed that killer whales seem to have high pain thresholds for incisions, barely reacting to syringes or minor cuts---but are very sensitive to pressure. Some trainers even talked about playing a game with killer whales at marine parks, where they’d try to touch a whale gently with their fingers without being noticed. They found that killer whales could detect even gentle pressure---not surprising, perhaps, for tactile animals that touch family members constantly. With this in mind, Lance and Graeme decided not to use crossbow bolts, because of the energy they impart and the momentary pressure they create when they hit. Instead, they devised ultra-light darts that they could fire very accurately with a pneumatic tranquilizer rifle. The darts are spun by the rifle which improves their accuracy, and at 12 g (approx. one tenth the weight of a crossbow bolt) they impact with much less energy. The darts have a stainless steel punch at one end that takes a plug of skin and underlying blubber the size of cigarette filter. After Photo: Graeme Ellis
the punch has penetrated, the nose of the dart reaches the skin Biopsy dart bouncing off a killer whale's back
surface, compressing it slightly and causing the dart to bounce out.
The dart floats tail-up until it’s collected from the water by the
researcher, and then the plug is removed and frozen or preserved.
Biopsy Sampling in the Field
In the first year of the project, Lance and Graeme discovered that resting killer whales were sometimes startled by a dart hit (or near-miss). In contrast, they found that actively-swimming killer whales rarely reacted in any discernable way when hit by the ultralight biopsy darts and were not more likely to avoid the research boat after darting than they were before. After two years of biopsy sampling killer whales in British Columbia, Lance began sampling killer whales in Alaska as well, working with his long-time friend and colleague Craig Matkin. Lance, Graeme and Craig now have well over 500 samples in the collection, enough to provide fascinating insights into the secret lives of their favourite species.
In the Lab
In the early years of the DNA study, Lance spent summers in the
field and winters working in a genetics lab in the Department of
Zoology at UBC. In 2002, Allyson Miscampbell took on much of the
responsibility for the DNA analysis, which she does in the Genetic
Data Centre in the Department of Forestry at UBC. Allyson’s
responsibilities include extracting DNA from tissue, purifying it, archiving part of it to ensure that it will be available for research for many years, and then analyzing it in various ways. She can quickly determine, for example, the sex of the whale from which a sample was taken, which population it belonged to, and with a certain degree of confidence, who it’s parents were. Click here for more information about how this project has helped us understand the relationships between resident, transient and offshore killer whale populations.