November 30, 2011 Weddell Seals at Turtle Rock
Yesterday the research team drove out to Turtle Rock to collect samples. Turtle Rock is a small island off the coast of Ross Island. It is located 15 kilometers North/Northeast from McMurdo Station. We went out there to collect sediment samples from the sea floor. We expect the sediment here will have less pollution than the diving sites closer to McMurdo.
Arriving at the dive hut
As we drove up to the dive hut in our Pisten Bully, I noticed dark spots along the ice. Were they islands? Cracks in the ice? As we got closer I discovered they were Weddell seals! There were over 50 of them basking in the sun and napping along the ice. The large number of seals made one thing evident: beware of cracks in the ice! Weddell seals live on the sea ice, but they dive down into the water near cracks in the ice, which serve as breathing holes. If you see seals on the ice, you can be sure there is access to the water nearby.
Up close with the seals
While Terry Palmer and Steve Rupp collected sediment samples on the sea floor, I spent some time observing the seals. A mother was nursing a pup nearby while other seals lounged on the ice. The seals would communicate in a variety of ways. Sometimes they would make creaking and clicking sounds, other times they would grunt and groan. If you listen carefully in the video below you can hear these sounds.
A seal's life
We saw many mother seals with their pups on the ice. From late August to early November, female Weddell seals crawl out onto the ice to give birth to their pups. Then the mothers spend about a month on the ice, feeding their young instead of feeding themselves. You can imagine the transformation these mothers undergo--their bodies change from being plump before giving birth to being quite thin (for a seal) after a month of nursing. The mothers at Turtle Rock have long bodies that are concave, while the pups show a convex shape.
Many of the pups at Turtle Rock were nursing, as you may have seen in the video. Seal milk is unusually high in fat. 60% of Weddell seal milk is composed of fat. That is very high compared to the fat content in other animal's milk: 3.9% for cows, 3.5% for goats, 6% for sheep, and 4.1% for humans. Weddell seal pups gain weight quickly while nursing. Most pups' weight double from their initial birth weight of 55 pounds in just 10 days. This is important since the pups' mothers will start nudging them into the icy water after they are one week old. By 7 weeks, the pups typically weigh around 240 pounds.
For more information on Weddell seals, click here
Why do you think the seals give birth to their pups on the ice? How is this a survival strategy?
Why is the Weddell seal's milk so high in fat? How is a survival strategy?
If a Weddell seal pup initially weighs 55 pounds, and doubles that weight in 10 days, how much weight does it gain on average every day?
If the Weddell seal weighs around 240 pounds after 7 weeks, how much weight does it gain on average every week? Every day?
Cool Careers in Antarctica
Meet Douglas Hilbrant. Without him there would be no food, fuel, or people in McMurdo. That is because he helps maintain the planes that bring all those things here. He fixes and keeps equipment running that supply electricity and air pressure to the planes when they are being prepared for flight. His official job title is aerospace ground equipment. Before coming here, he was a mechanic in Florida. He grew up surrounded by aviation in Pensacola, Florida, which hosts a naval air station. This is his first season in Antarctica. He arrived on August 21st.
Interested in this career? Click here to learn more!