August 11 – After a month of watching and waiting, today we finally caught three narwhals. They were three nice big males, all between 4,5 and 5,0 m long with 2 m impressive tusks. We could see from their size and activity that they were very healthy. The first two whales were together in one net and the third was caught 2 hours later in another net. The first thing we discovered with the infrared thermal camera, that we use for measuring skin temperature, was that the whales were very warm along the dorsal ridge, and that this area is an important part of the body for dumping excess heat. The water was cold so fortunately the whales did not overheat and the surface temperature of the whales dropped while we were handling the whales. The bad news was that our thermal camera got wet when one of the more energetic whales splashed water with his tail! – it may be ruined for the rest of the field work, but we will try to dry it in rice and see if it recovers.
All three whales received special satellite transmitters that provide very detailed positions of their movements at sea. Essentially positions of all surfacings of the whales will be collected which will allow for very detailed mapping and analysis of their daily activities here. After 1 September the computer settings in the tags are changed to conserve batteries and we only receive daily positions of the whales; that way the tags can continue to provide coarse information on movements for up to a year.
The three whales also received acoustic recorders that will record all the sounds produced by the whales and also show their dive profiles. The recording of vocalisations will tell us where and at what depths the whales are most actively feeding. Importantly, the acoustic tags will also tell us the sounds in the environment that the whales are exposed to and how they react to them. For example, we will be able to study the sound pulses that seismic ships emit during exploration for oil and gas under the seafloor. Dive profiles while subjected to those sounds will show us how the whales react to different noise levels and how they use the water column.
Two of the whales were instrumented with heart rate recorders, to see how their heart rate changes as response to underwater noise. Before they were attached to the whales with suction cups, we monitored the heart rate signals using a miniature heart rate computer to make sure that the two electrodes on the skin of the whales were in the right positions to provide optimal signals. The heart rate signals were not as good as expected, and we first thought it was because these were very fat whales (thick blubber tends to weaken the heart rate signals on the skin). However, we later discovered that there was a problem with the wiring of the field recorder, which assured us that good signals would be received from the instruments that we left on the whales. It was fortunate that we did not give up!
The heart beat on a whale drops from about one per second to once every 10 seconds when the whales are diving. (Your resting heart rate is about 1 per second, and even faster if you are very young or out of shape.) When we handle the whales, their heart rate can go down to the low rate, which makes it hard to know if the signal is good enough for our instruments.
Finally a tiny sample of the skin was collected from the whales and that will be used for genetic studies of the relationship between whales from this area in East Greenland and whales further south or at Svalbard.
All three of our whales, who we named Bjarne, Helge, and Thor (the wild whale that splashed and ruined our thermal camera) were released after about half an hour. Our team cheered as they swam away with the instrument packages. As long as the instruments stay on the whales, we will be able to follow them on the internet. In one day, we have already tracked them heading east out through the fjord, Bjarne and Helge traveling together and Thor on his own. All were doing fine. What a glorious sunny day with a breakthrough in the tagging operations. It was worth all the time we have spent waiting for this important moment.
Cover photo: Carsten Egevang