How to radio track a tag

It seems the whales have wised up today.

We worked with a couple this morning and another this afternoon and each one was less cooperative than in previous days. But they were smaller animals and so perhaps less tolerant of our presence. Plus, we are using a tag with an extra piece to it, which makes it less easy to deploy. So we struck out today in terms of tagging.

We did, however, get good photo-ID images of three animals and a skin sample—a total of five so far, which is beginning to look like a sample set worth looking at for the planned dietary studies.

Julie van der Hoop listens for a tag.
(Luis Lamar, Advanced Imaging & Visualization Lab, WHOI)

Perhaps this is a good time to tell a bit more about how we recover the tags. Because they are slightly buoyant, the tags slowly rise to the surface after releasing from a whale. Once at the surface, their radio transmitter broadcasts a steady beeping, which we can hear using directional antennas (hand-held and installed on the ship) and a suitably tuned radio. With these, we can acquire a bearing on the tag and move in that direction. As we approach the tag, the signal gets stronger and stronger.

The signal of a tag floating at the surface is very different to one from a tagged whale. While on a whale, we detect a periodic chirp or two as the animal it is on surfaces every 45 to 60 minutes, especially as the whale arches to dive; once on the surface, the tag beeps continuously. Once we get a visual sighting of a tag in the water, which is by no means easy, we then maneuver nearby so we can retrieve it using a dipnet.

Leigh Hickmott detects the missing tag.
(Marta Guerra, University of Otago)

The other day, we had to leave a recalcitrant tag on a whale (one that we'd been trying to recover for two and a half days) and head for shelter. Once on shore, we climbed the nearest hill to get a better vantage point to listen for the tag. There was jubilation when we finally detected it, and we carefully took a bearing so the ship could run down the bearing to relocate it. Once back on board the sense of relief was palpable. It had been stuck on the whale for 36 hours or more and it had been causing more than a little loss of sleep.

Leigh Hickmott retrieves the errant tag from the bow of the ship.
(Luis Lamar, AIVL, WHOI)

So that might give you a bit more of a sense of the various skills our team has: radio tracking, tag application, photography, boat driving, microelectronics, data analysis—and a boat load of patience.

Tonight our aerial imaging team will test fly their new bird on shore so that it can get a sense of which way is up before it gets to fly off the ship tomorrow. Hopefully. Some of you older comic readers might have a sense of what it has been christened.