Sealos in the Pack Ice #3

from Tim Page

on board the Australian Icebreaker "Aurora Australis"

in the pack ice off Terre Adelie, eastern Antarctica

December 10, 1999, 4:45pm

G'day to the students and staff of Doyon and Winthrop Schools, and

particularly to the classes of Ms. O'Brien, Ms. O'Reilly, Mr. Beal, Ms.

PRESENT POSITION: 63 degrees South Latitude, 136 degrees East Longitude

DIRECTION HEADING: 300 degrees

SHIP SPEED: 12.4 knots

DISTANCE FROM TASMANIA: 1297 nautical miles

DISTANCE TO DAVIS STATION, ANTARCTICA: 1461 nautical miles

AIR TEMPERATURE: -2.6 degrees Celsius

WATER TEMPERATURE: -1.6 degrees Celsius

WIND SPEED: 2.9 knots

HUMIDITY: 91%

Yipee! We finally made it to the pack ice! For the past couple weeks, we

have been passing through the Southern Ocean, heading south to Antarctica.

A few days ago things started to change. We saw our first iceberg, which

looked like a giant floating ice cream sundae. Icebergs are huge chunks of

frozen fresh water that have broken off of glaciers and ice shelves on the

continent and floated north through the ocean.

Then a day of so later, we came to the pack ice. This is where the ocean

has gotten so cold that even salt water will freeze. So as far as you can

see there is white sea ice, with enormous icebergs poking through here and

there. As soon as you reach the pack ice, the animals change. While in the

ocean, there were piles of oceanic sea birds flying around the ship,

especially giant albatrosses and little prions. When you get to the new

environment of the ice, they disappear and all of a sudden there is a whole

new group of animals. Little white Snow Petrels and black and white

Antarctic Petrels dart around the ship. Little Adelie Penguins fly through

the water with as much grace as the other birds fly through the air.

Human-like Emperor Penguins on their ice floes stare calmly as our giant

orange ship ploughs through the ice past them. If you look carefully, you

can also sea seals relaxing on the ice. When the ship comes too close, they

get annoyed and snarl a bit, but mostly they just lie there.

You see, seals are why I am here. Last year I came down to Antarctica to

help with a pack ice seal survey. We had a teeny weeny little problem, the

propeller on the ship broke and we got stuck in the ice. This meant we

couldn't finish the survey, so we are back again this year to finish it off.

I suppose the next question is why are we surveying seals? We are not

asking them their opinions on the latest movie, it's not that kind of

survey! What we are doing is counting them. We need to know how many seals

there are, and what kind of seals are there. We need to know this so we can

better understand how the Antarctic ecosystem works. Because it's such a

hard place to get to, people don't know much about it. We have to learn how

all the animals interrelate with each other and their environments, so we

can be sure not to mess it all up.

There are 16 of us "sealos" on board the ship. Most of us are from

Australia, except Yuzuru from Japan. We have all done many research

projects on lots of different species of animals, so everyone has good

stories. Julie is the veterinarian who makes sure the seals are all right.

She used to work at London zoo in England and so has lots of experience with

animals from all over the world.

Two nights ago, Julie had her hands full. We decided to go for a seal

capture. This isn't as scary as it sounds. What it means is that she,

Colin (the boss), and three others were lowered over the side of the ship

onto an ice floe by crane. Julie then sedated the seal so Colin could

attach a satellite tag to its back. This tag keeps track of how much time

the seal spends on the ice, how much time in the water, how deep it dives

and where it goes. It then sends all this information by satellite back to

Australia. In a few weeks the seal moults, which means it loses its hair

and grows brand new hair. This is when the satellite tag falls off the

seal's back, so it isn't stuck with it for long.

The next question is why do we glue this silly thing to the poor old seal's

back? Actually it's very important for our survey. We count all the seals

we can see on the ice, but seals spend a lot of their time in the water,

where they are almost impossible to see. So we use the information from the

satellite tag to estimate how many seals there are in the water and add them

to the seals that we can see on the ice to get an idea of how many there are

all together.

There are four main types of seal we expect to see in the pack ice. The

Crabeater seal is the one we see most. They vary in colour from white to

brown, and have dog-like snouts. They don't eat crabs at all, but eat those

little krill things that are so important in this part of the world. Nearer

to the continent, we see big, fat Weddell seals, which are dark with light

spots and have little pussy cat type faces. Occasionally we see Ross Seals,

which look like short, fat, dark slugs, with little tiny beak-like faces.

And finally and most impressive, we see big Leopard seals. They are an

important predator and eat other seals, penguins, fish and even krill. They

have a long, powerful body and a big reptile-like head.

Because seals spend so much time in the water, they need a way of

communicating with each other. As you probably know, sounds travel much

better in water than in the air, so many marine animals use sound a lot. I

suppose most famously would be the Humpback Whale, which you guys can see

just off the coast of Massachusetts at the Stellwagon Bank. Seals also use

sound. The male Weddell Seal makes lots of sound to warn other males to

keep away from its bit of underwater territory and to tell the females to

"come on over to my place".

You know how I mentioned that our survey had a problem counting seals in

the water? We have a special problem with Leopard Seals. We almost never

see them, but when we lower a water microphone (hydrophone) over the side of

the ship, we always hear them. So we know they are there but how do we

count them? Well it so happens we have two scientists on board, Kate and

Michelle, who study acoustics (the science of sounds) and Leopard Seals.

Here's what Kate has to say:

"Underwater Acoustic recordings of Leopard seals:

Leopard seals are one of four species of pack ice seals which live in the

sea ice surrounding Antarctica. Because they feed and breed under the ice

they need some way to communicate with one another under the water. With

the use of underwater microphones we have found that you can hear the

leopard seals 'singing'. They use particular calls like we use words to

give other seals messages. They call most often at night during the summer

months when they breed.

No one knows exactly how many leopard seals there are in Antarctica. They

are one of the top predators in the Antarctic food chain, they eat fish,

squid, krill and even penguins and other seals. As such, they are an

important indicator of how things are running within the Antarctic

ecosystem.

We are recording and counting the calls leopard seals make underwater as a

way to estimate how many of them there are in a given area. The calls are

quite amazing, some sound like eerie ghosts while others sound like birds

chirping!

Using the hydrophones we can hear all the underwater noise. There is the

noise of the ship and also the calls of whales, fish and snapping krill as

well as those made by other types of seals. It makes you realise that there

is so much happening down there beneath the surface of the ocean that we

cannot see from up above."

So there you go, a visual survey is not the only way to estimate numbers of

animals, and I figure the best way is to use all the different methods

together to try and unravel the workings of the Antarctic ecosystem. Thanks

Kate.

Oh yes, as a special treat, Kate & Michelle have given me a short recording

they have made of Leopard seals under water, and I have emailed it along

with this message. Amazing, eh?

RESEARCH QUESTION

---------------------------------

I've got to go and do some work. Can you find out about other animals that

use sound as an important part of their lives? I mentioned whales, but many

animals use it, like birds and bats and dolphins. What do they use it for?

Oh yeah, almost forgot. I will finish by answering some questions from Miss

O'Brien's Class.

1) How many penguins did you actually see?

Actually it's pretty hard to count. The numbers on Macquarie Island were

unbelievable. In one place, Lusitania Bay, there are an estimated 500,000

King penguins!!!!! That's a lot. Also on Macca, I saw 3 Royal Penguins,

about 300 Gentoo Penguins, and about 30 Rockhopper Penguins. There are

different penguins in the pack ice. Here there are Emperor Penguins (the

great big ones) and Adelies (cute little ones). I have seen about 100

Emperors and about 500 Adelies. The largest group of Adelies was 65 that

were standing about a third the way up an enormous iceberg. It was really

steep, so it must've been hard for them to climb up there. The ice was

coloured pink, because they eat krill and so their poo is krill coloured!!

2) Have you ever tripped over an animal?

On Macquarie Island I almost tripped over Elephant Seals on the beach

because there were so many. A couple years ago I did actually trip over a

seal. I was on Codfish Island, which is a very small island off the

northwest coast of Stewart Island, which is itself at the very bottom of New

Zealand. I was there to help with a project researching an endangered

flightless parrot called the Kakapo. I went for a walk on the beach and

stepped over some rocks, but they weren't rocks, they were big New Zealand

Fur Seals! And they weren't happy to see me. I tripped over and then

climbed up the nearest real rock quickly, since they have big teeth!

3) How many people are actually with you on the trip?

There is a total of 110 people. 25 of them are the ship's crew. There are

16 of us "sealos" and about another 20 people doing other research projects

off the ship. The remaining 49 people will be getting off the ship at

either Davis or Mawson Stations on the continent.

4) Did you know any of these people before the trip?

I knew about half of the sealos from last year, plus a couple guys on the

crew, and Mike who studies algae in the ice and Simon the krill biologist.

5) When are you planning on returning to Australia?

I plan to be back in Australia at the end of January, but these voyages

often have delays, so I don't really know. I am then flying to London,

England, which is where my wife and I are living at the moment. I think my

wife, Kaye, may want to see me then!!

Have most excellent holidays if I don't get to write again before vacation.

See ya!

Tim

PS STOP PRESS - IMPORTANT

As I'm writing this, the sealos in the Capture Team are just coming back to

the ship after succesfully putting a satellite tag on a Ross seal for only

the second time in history. Some American scientists in the 1980's put one

on a Ross for 3 days, but no-one has managed to do it again, until now! It

means we will learn a lot about how Rosses live, what they do and where they

go.