Science Update

Today is day 10 of the current incubation experiment. We were planning to set up incubation experiment #2 today, however, the winds are making it a little difficult. Today may end up being a day to catch up on data entry and prepare bottles and filters for a long day of incubation set-up tomorrow.

TGIWF - Thank Goodness It's Wildlife Friday

This past week we were able to spend time in the Erebus & Terror Gulf and Duse Bay. These areas are on the eastern side of the Antarctic Peninsula. According to our captain Brandon Bell, this area is not visited as much as the western side of the peninsula. Knowing this, I was sure to be on the bridge during my free time to observe and photograph this beautiful location. When we entered Duse Bay, everyone on the bridge was struck by the beauty. Large glaciers nestled between volcanic ash-covered mountains. The sun was shining brightly off of the fast ice (ice connected to the coast) and the light winds created small ripples on the water. As we approached the fast ice, small dark dots appeared on the fast ice. Some were skuas (birds), but most were seals.

Fast ice, ice floes and seals
On approach to Duse Bay in the Weddell Sea, ice floes can be seen floating away from the fast ice. The small dark spots on the ice are sleeping crabeater seals. Photo from the bow of the RVIB Palmer.

Crabeater seals on fast ice
From the bridge of the RVIB Palmer looking down on the fast ice. Groups of crabeater seals are seen scattered across the ice, even off in the distance.

Since we spent a number of days near these seals, I decided to highlight this interesting pinniped species for this week's wildlife Friday.

Crabeater Seals (Lobodon carcinophaga)

Crabeater seals (Lobodon carcinophaga) are one of the most abundant species of marine mammals in the world. They are estimated at the low range of 10-15 million and at the high range at 50-75 million individuals. Crabeater seals are large, slender seals that are found only in Antarctica. These seals reach average lengths of 6.5 ft and weigh close to 500 lbs. Crabeater seals appear long and slender in comparison with other seals from this area, especially the very rotund Weddell Seals (Leptonychotes weddellii). Crabeater seals range from tan to dark brown to any shade of grey. Young crabeater seals usually have a dark dorsal (back) side and a light ventral (belly) side. This is referred to as counter-shading and is a way to help protect the young seals from predators like leopard seals and orcas. Crabeater seals also differ from other seals in this area because they tend to form large groups that rest on the ice together, or forage together in the water.

Group of crabeater seals
Crabeater seals are known to congregate into groups. This group of fifteen crabeater seals is not uncommon in Antarctica.

Crabeater seals survive on a diet of krill. In fact, krill makes up about 90% of their diet. Most other seals rely on fish or, in the case of leopard seals (Hydrurga leptonyx), small seals and penguins. Because most other seals do not primarily eat krill, the crabeater seals have very little competition for food. Crabeater seals have highly specialized teeth to help them filter krill from the water. These krill-filtering cusps are found along the sides of the seals mouth. As the seals gulp water, they can push the water through small openings in the teeth. This traps the small shrimp-like crustaceans in their mouth, while the salt water filters out.

Crabeater seal teeth diagram
By Dimitri Torterat (Diti) (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons

Crabeater seals generally forage at night when the krill move from the deep waters to the surface. The seals can forage along the edge of the fast ice and may even swim under the ice to feed on krill. Watch the video below to see these crabeater seals in action.

Author
Date
Weather Summary
Cloudy and WINDY! Wind speeds above 45 knots most of the morning. Large seas even in protected area
Temperature
0C/32F
Wind Speed
45+ knots
Wind Chill
-20C/-4F

Comments

Cara Pekarcik

Hi Alanna - that's a good question, but one that I unfortunately can't answer (yet). I haven't been able to find the answer, but I am still
looking!

On 2016-09-26 06:52, PolarTREC wrote:

Cara Pekarcik

I have not found any information on life span. It is possible that no one has studied seals throughout their natural life span.

On 2016-09-26 06:48, PolarTREC wrote:

Cara Pekarcik

Shannon - I think I provide this information in the journal, but just in case I left it out...crabeater seals can reach about 6-7feet in
length and weight a couple hundred pounds.

On 2016-09-26 06:45, PolarTREC wrote:

Cara Pekarcik

Rebecca - I am excited any time I see something new in this area. There are not many people that get to experience the beauty of this area
or the animals of the area. I have smiled and laughed at many sightings
during this research cruise.

On 2016-09-26 06:41, PolarTREC wrote:

Cara Pekarcik

Hi Morgan - I have been trying to answer this question myself. I will certainly let you know if I figure out the answer.

On 2016-09-26 06:36, PolarTREC wrote:

Cara Pekarcik

Hi Brianna - crabeater seals have a very specific diet in comparison to most seals. I am not sure what you mean by a normal seal (remember,
there are many different species of seals), but if you compare a
crabeater seal to a harbor seal (something we typically see in New
England), you would notice a slight difference in body shape, a
difference in tooth anatomy, a difference in diet. Possibly, there
would differences in their vocalizations, mating season, habitat, etc.

On 2016-09-26 06:34, PolarTREC wrote:

Cara Pekarcik

Hi Eric - I think I mention this is a few journals - the wind is the biggest
concern. If the wind is blowing hard, deployment depends on whether the
ship can easily maintain position and whether or not the crew and
equipment can stay safe during deployment.

On 2016-09-25 16:46, PolarTREC wrote:

Jon Knowles

Do Crabeater Seals have a specific diet to crabs, hence the name, or do they have another primary animal for their diet, not related to the crab family

Cara Pekarcik

Hi Jon - look back at this journal on crabeater seals to find the answer to this question.

From: PolarTREC
To:
Sent: 10/24/2016 7:42 PM
Subject: Re: Jon Knowles commented on 23 September 2016 Crabeater Seals

Angela Y, Block F

In the diet of crabeater seals do they eat anything other than krills?

Cara Pekarcik

90% of their diet is krill, so that leaves 10% for other sources. These can be fish or squid.

On 2016-09-26 18:59, PolarTREC wrote:

Andrew Tobin

What is the main competitor of the crabeater seal when it comes to their eating of krill?

Vivian Tran

Hello Mrs. Pekarcik. You mentioned ash-covered mountains. Does this mean that there are volcanoes even on Antarctica? Also, the picture of the group of crabeater seals remind me of fish, except they are more chubby. The video of the seals swimming reminds me of dolphins. They are absolutely adorable.

Cara Pekarcik

Hi Vivian - Yes! There are volcanoes on the Antarctic continent. The tallest is
Mount Sidley and the second highest is Mount Erebus. Mount Erebus is
also the southern most active volcano on Earth.

On 2016-09-23 10:17, PolarTREC wrote:

Kevin C, Block B

Do the Crabeater Seals spend more time resting on the ice or swimming in the water?

Cara Pekarcik

Hi Kevin - I am sure it depends on the amount of food available and whether the
seals are tired.

On 2016-09-23 11:45, PolarTREC wrote:

Reina C, Block B

In today's journal you didn't mention anything about the Crabeater Seals even eating crab. So I want to ask if the 10% of their diet are crabs? This next part is not a question, but an interesting fact. So I noticed the seal is named Lobodon Carcinophaga, and I remember from this year's summer reading, carcinoma is cancer. I thought, how are they connected? I looked it up and the Greek word karkinos means crab, but why does it also mean cancer? A ancient greek physician named Hippocrates was the one who named a cancer tumor a carcinoma. People have said tumors reminded him of the hardness of a crab shell or of when a crab claw pinched you. I hope this was as interesting it was for you as it was me.

Cara Pekarcik

Reina - I am so glad you caught that. I did not mention anything about crabeater seals eating crabs. The amazing thing is - crabs are not
found in Antarctica! Crabeater seals don't eat ANY crabs. In all of my
research, I still have not figured out why they are named crabeater
seals, but I will keep looking.

I love this information about the scientific name of the crabeater
seal. I had no idea that karkinos meant crab and I didn't know the
origin of the term cancer. Nice connection to the Henrietta Lacks book!
In astrology, cancer is also the sign of the crab. Now I am really
interested as to why crabeater seals have this name! I will see what I
can find out - feel free to do the same and we will compare notes.

On 2016-09-23 13:53, PolarTREC wrote:

Yi L, Block A

How fast can a crabeater seal swim?

Cara Pekarcik

Hi Yi - I have found some conservative estimates of approximately 13km/hr (8mph). This information was based on satellite tracking data.
I have not found any specific studies that have tagged individual
crabeater seals to determine speed.

On 2016-09-23 18:59, PolarTREC wrote:

Cara Pekarcik

Reina - just another additional bit of information. Lobodon translated to 'lobed-toothed'. It still doesn't answer the question of the 'crab'
name, but it does show the importance of their unusual dentition.

On 2016-09-23 13:53, PolarTREC wrote:

Jessica A, Block F

I'm loving these wildlife journals because they are so interesting! But you mentioned that crabeaters only live in Antarctica is there a reason why?

Adina Dildine

During casts, how does the RVIB Palmer maintain a relative location despite the waves without anchoring? How long does it take to complete one cast?

Cara Pekarcik

Hi Jessica - I am not sure of the evolutionary history of the crabeater seals, but
it is possible that they evolved here once Antarctica was separated from
other continents.

On 2016-09-24 07:29, PolarTREC wrote:

Cara Pekarcik

Hi Adina - great question!The ship has a dynamic positioning (DP) system that allows them to use
both bow thrusters and the stern propulsion to keep the vessel in
position. It is impressive! Today, we were in 40-45 knots of wind and
we were holding position quite well during the cast. Each cast is a
different length of time depending on depth. One night, we did a deep
cast to close to 3000m/9000ft. The cast took a little over 4 hours.
Today, however, we only did casts to about 75m/150ft and they only took
about 20 minutes. It really depends on the depth (and the speed at
which the rosette is lowered or raised). Miss you!!!

On 2016-09-24 09:59, PolarTREC wrote:

Tengfei L, Block B

Hi Ms. Pekarcik, it's interesting when you are talking about the seals. Do you know why does the Crabeater Seals does not have visible earflaps?

Cara Pekarcik

There are probably very few because the crabeater seal relies on krill for almost all of its diet. Other seals and animals in the area may eat
krill, but they may also take advantage of the small fish and squid in
the area. Humpback whales may be the main competitors in the summer
months.

On 2016-09-30 06:51, PolarTREC wrote:

Cara Pekarcik

Hi Tengfei - most marine mammals have evolved to have very streamlined features. This lack of ear flaps may serve the purpose to keep the
seal's body streamlined in the water. It may also have to do with the
way sound moves through the water and whether or not the seals require
directional hearing to detect predators or food.

On 2016-09-25 05:35, PolarTREC wrote:

Jason W, B Block

Hi,I was wondering how the weather is like out in Antarctica and how frequent does it interfere with sample collection, experimentation, etc. And if the weather our there also affects your capabilities to access the internet.

Cara Pekarcik

Hi Jason - if you look back through the journal postings, you can get a sense for the weather (it is posted at the top of the page). We
generally have temperatures around 0C/32F with high winds. This can
create some pretty cold wind chills and high seas. The seas can hinder
our sampling efforts if conditions are unsafe to deploy equipment. To
my knowledge, the weather has not affected our email or Internet access.

NOTE: we are currently between weather systems and we are going to try
to head back out to the Drake Passage for a few samples before head back
to the coastline.

On 2016-09-25 08:38, PolarTREC wrote:

Eric H Block F

What kind of weather makes it unsafe for data collecting and is the wind the main problem stopping you guys from collecting data?

Brianna s Block G

What is the difference between a Crabeater seal and a regular seal?

Morgan Murphy

Why are they called crab eater seals if they eat krill?

rebecca podgurski

what was your reaction when you first saw these seals since they're only found in Antarctica

Loretta C. Block F

Hey Ms. Pekarcik Was there any chances that Crabeater Seals swam by the boat?

Cara Pekarcik

It is always a possibility. The video of the crabeater seals swimming was taken from the ship - they weren't that far away. They could be
swimming around the vessel below the surface of the water, too.

On 2016-10-02 17:04, PolarTREC wrote:

shannon doyle

about how big are the seals

emily butruccio

how long are the seals life spans

Alanna Sweeney…

Why are the Crabeater seals named that even though they dont eat crab

Aidan G Block G

have you seen a good amount of these seals in your time down there?

JudyL Block G

why doesnt the crabeater seals dont eat crabs?

Cara Pekarcik

There are no crab species that live in this area of Antarctica, so they aren't able to eat any.

On 2016-09-26 07:00, PolarTREC wrote:

Cara Pekarcik

They are a fairly common sight in the locations we have visited. In two different locations, we estimated a few hundred crabeater seals.

On 2016-09-26 06:58, PolarTREC wrote: