Equipping seals with satellite transmitters: The second field season
Ringed seals and bearded seals are being equipped with advanced satellite transmitters, which will provide scientists with detailed information about the life of the seals and how they adapt to climate change.
So, we are now underway with our second field season in the ringed seal ICE programme. Our fieldwork this year will again primarily involve capturing ringed seals and instrumenting them with advanced satellite tags.
The satellite tags we are using in this research programme provide the standard information on where the seals are, how deep they are diving and for how long, but in addition they sample hydrographic data (salinity and temperature) as well as information that provides insight into primary production in the regions where the seals swim and dive.
These detailed data sets will allow us to study habitat choices made by ringed seals. We will be able to explore their general activity patterns, identify foraging areas, and study their movement patterns – all in relation to sea ice availability.
This year we will also attempt to instrument bearded seals with satellite tags that record the same hydrographic and behavioural measurements as the ringed seal tags, in order to explore the same sorts of questions with this other High Arctic ice-seal; but these prototype tags also have a new twist (see below).
Bearded seals are a little-studies species that is found throughout the circumpolar Arctic. They give birth on small ice floes late in the spring in shallow water areas, often near the coast, because they find most of their food close to the sea floor or even in soft bottom sediments such as mud or sand. Their ice-associated birthing in combination with their specialized feeding in benthic environments might make them quite sensitive to changes in sea ice availability.
Annual sea ice “feeds” the bottom community when it melts over vast areas dropping organic matter and nutrients to the sea floor. Because there are strong indications from our earlier studies, and the experience of hunters around the Arctic, that adult bearded seals have quite restricted ranges, we have worked with our colleagues at the Sea Mammal Research Unit at the University of St Andrews in Scotland to make a new prototype tag that gives us GPS positions, rather than the less accurate ARGOS positions that are based on Doppler-shift measurements.
The cruder ARGOS positions are reasonable to use when seals wander over thousands of kilometres during their annual migrations, like our ringed seals from last year did. But, if the seals are very stationary, like we think adult bearded seals might be, we need instruments that give us much more precise data on location of the animals to sort out what they are doing where. We hope that the new prototype will do exactly this for us.
Meridian is both our home and our means of long-distance transportation, which allows us to shift working areas easily based on ice and weather conditions (especially wind directions and strengths). But, we use rubber boats on a daily basis during our capture work, to transport us and all of our nets and gear from place to place within a given area.
Ice conditions this year are such that we were unable to go up into the Rijpfjorden area, where we had planned to work, vast amounts of drift ice from the high north have come south, ironic to be stopped by ice in a year with so little annual ice around Svalbard.
The master-plan is that 2 of our 3 field seasons would be based up in the Northeast corner of Svalbard, so we hope that ice conditions co-operate next year so that we can work in that area again.
In any case, we are now working on the west coast of Spitsbergen, and will in the first instance concentrate on capturing seals in the Kongsfjorden–Krossfjorden area. Many marine biology and oceanography studies take place in this region, working out of the various international research stations in Ny-Ålesund, that will benefit from the measurements that we hope the seals will provide, while we will also benefit from the additional information we can access from others studying in the area, to put our results in a broader perspective.
This year’s departure into the field took place on the 15th of July, from Longyearbyen and following the sail up we have concentrated our first working week here in Kongsfjorden. When this letter is being written (25 July), we are on our way into Krossfjorden because the glaciers in Kongsfjorden have calved so much ice into the water that we cannot find places to set our nets without them being packed with glacier ice-pieces in no time.
We have deployed 3 satellite tags on ringed seals thus far. Last year the largest seal we captured weighed just over 60 kg, while the 3 we have tagged in Kongsfjorden are super fat, with the largest animal weighing over 100 kg.
This latter animal is a record for this region, but the other two were also very fat, each weighing over 80 kg. Food availability here must be quite extreme this season.
The satellite tags are simply glued to the seal’s hair with fast-setting epoxy. All seals replace their coats once per year at a set season, moulting the old hair and replacing it with a shiny new coat.
Because the tags are rather expensive bits of equipment, we try to catch seals just after the moult, so that the tags stay attached for as long as possible. The ringed seals have clearly just finished the moult, so our timing is perfect for deploying instruments.
However, the situation is different for the bearded seals; many of them are in the middle of their moulting period. In this state, they are not suitable for our study, so we are finding that we have to search long and hard to find bearded seals that are ready to wear our equipment.
Thus far, we have captured two large adult animals that had fresh new hair, so these two individuals now wear tags that have never before been deployed anywhere in the world.
On this species, we set the tags much further down the back than on ringed seals. This is because the two species swim very differently; ringed seals surface with their heads out of the water, but show little of their backs, while bearded seals like to float on the surface while breathing, with their backs exposed.
During last year’s field work in Nordaustlandet, we were often harassed by polar bears when we were on land guarding our nets. Here in Kongsfjorden–Krossfjorden there is longer gaps between bear sightings, but they are not totally absent here either.
We had a curious male bear that we met on Gerdøya in Kongsfjorden a few days ago, and the same day we saw an adult female with a satellite collar chasing reindeer high up on the slopes of Ossian Sars just beneath the bird cliffs deep in Kongsfjorden.
Back to work …
Best regards for now,
Kit and Christian