Dan Costa, aboard the Yuzomegeologia, returning from Antarctica -- We weren't sure it would work....but we did it! We tagged four leopard seals!
When I first went to Cape Shirreff, a remote outpost in the Shetland Islands, in the late 1990's, you could count on seeing the occasional leopard seal. If you were lucky, you might see a leopard seal take a pup or a penguin.
However, things have changed dramatically on the Cape in the last 10 years. Researchers here see leopard seals almost every day. On one day this season, our Chilean colleagues counted 22 leopard seals!!!! Now, if you consider that leopard seals are probably feeding exclusively on fur seal pups and pre-fledgling penguins, that's a lot of pups and penguins that are being caught and eaten by leopard seals, who must maintain their 9-foot-long (2.8 meter) , 700-pound (320 kg) bodies!!! Female leopard seal are larger and heavier than males, and can weigh up to 880 pounds (400 kg).
So, to better understand this, Mike Goebel of the U.S. Antarctic Marine Living Resources program initiated a pilot project to put satellite tags on leopard seals. As our Chilean colleagues had attached simple numbered tags to the flippers of leopard seals, we knew that many leopard seals regularly returned to the Cape. However, we didn't have any idea as to whether they remained at the Cape or if they migrated away.
To answer that question, we attached satellite tracking transmitters to four seals; on three of them we were also able deploy time-depth recorders. We did this by lightly sedating the seals with Midazolam. (Physicians and dentsits also used Midazolam to sedate humans.) This made the animals sufficiently sleepy and lethargic so that we could carefully glue the transmitter and dive recorder to the animals' backs. The seals were still very much awake and capable of some movement, so we had to do this very carefully!!!!
Now we'll watch to see where the animals go. With any luck, the seals will return next year, and we'll be able to recover the time-depth recorder tags to retrieve the data that show how deep the seals dive and how long they stay underwater. The photo above shows Mike and researcher Gitte McDonald checking out a recently tagged seal, and below, they're measuring the length of one of our sedated seals. As you can see, the seals aren't that asleep!!!