By: Callum Lilley
Senior Ranger, Marine – Department of Conservation, Taranaki, New Zealand
During the end of January, I had the privilege to be part of the research team studying blue whales in the South Taranaki Bight, New Zealand. My role, along with assisting with visual survey, was to obtain biopsy samples from whales using a Paxarm modified veterinary rifle. This device fires a plastic dart fitted with a sterilized metal tip that takes a small skin and blubber sample for genetic and stable isotope analysis. This process is very carefully managed following procedures to ensure that the whales are not put under any undue stress. Biopsy sampling provides a gold mine of genetic and dietary information to help us understand the dynamics of this whale population.
Although firing a dart at a creature that is considerably larger than a city bus sounds reasonably easy, it is rarely the case. The first challenge is to find whales within a large expanse of ocean. The team then needs to photograph the side of each animal and take note of any distinctive features so that each individual is only sampled once. Sometimes other work will be undertaken (such as collecting fecal samples, or deploying a drifting hydrophone or unmanned aerial system/drone). Finally the team will attempt to get close enough to the whales, while taking care not to unduly disturb them, to get a biopsy sample. Wind, vessel movement, glare, the length of time whales spend underwater and the small target they sometimes present above the water are further challenges.
The video below shows a successful biopsy attempt. It is a well-coordinated team effort that relies on great communication. You can hear observer Todd Chandler direct the skipper of the vessel Ikatere into position while keeping me (the biopsy sampler) informed as to which whale is surfacing and where. From the vantage point of the flying bridge, Todd can see the whales’ position and movement (my view is limited from the lower deck). Todd points out where the whale is surfacing and it momentarily presents a target. This was the second sample from the two racing whales previously discussed by Dr. Torres, so it will be interesting to see their relationship to one-another.
The ideal angle to approach a whale to take a biopsy sample is from behind at a 45 degree angle, as this causes the least disturbance. The following video was taken from an unmanned aerial system. It shows the vessel Ikatere approaching from the whale’s left flank. Department of Conservation (DOC) biodiversity ranger Mike Ogle is on the bow of the vessel and fires a biopsy dart at the whale. After the biopsy is taken the vessel maneuvers to collect the dart/sample from the water while the whale continues to travel.
In addition to blue whale samples, the DOC permit issued to Oregon State University also allowed for opportunistic sampling of other whales. The following video was taken during an encounter with a large pod of pilot whales. The video shows how the lightweight dart bounces off the animal and floats in the water. Care is taken to communicate its location to the skipper who positions the vessel so it can be retrieved with a net.
Once samples have been retrieved they are handled very carefully to prevent contamination. The sample is split, with some preserved for genetic analysis and the rest for stable isotope analysis. Analysis of genetic samples provides information on sex, abundance (through genetic capture-recapture, which is calculated by analyzing the proportion of individuals repeatedly sampled over subsequent seasons), and relationships to other blue whale populations. Stable isotope analysis provides information on diet. Also, a portion of all samples will be stored for potential future opportunities such as hormone and fatty acid analysis. It blows me away how much information can be gleaned from these tiny samples!