First Trip to Turtle Rock
The weather began to clear yesterday afternoon, as predicted. The sun was out, and air temperatures (before wind chill) were between +7°F (-14°C) and +12°F (-11°C)! Since we finally had some nice weather, we decided to go scout at a location where we plan to work this season – Turtle Rock – to see how many and which seals were hauled out. We used the morning to prepare to go out on the sea ice, as the seals tend to haul out more in the afternoon. We gassed up the Pisten Bully and headed out of town. Before driving onto the sea ice, we checked out with the Firehouse on the radio, according to the standard safety protocol. You always want someone to know where you are going in case you need help! We followed the flagged route to make sure we would cross the big cracks at the marked safe crossings. Currently, the ‘road’ takes everyone south of McMurdo before they can go north (where our field sites are), to avoid the active parts of Backhoe Crack. As we neared the turn that would put us onto Cape Evans Road, the main route leading northward across the sea ice, the winds picked up intensely and created a ground blizzard that obscured our view of the flags. We had not yet crossed Backhoe Crack, and despite having a GPS unit with the sea ice routes, we could not navigate without seeing those flags; so we stopped moving and waited in the Pisten Bully as snow swirled past us. It looked as if someone had turned on a fog machine and tried to blow the fog with a fan big enough to power a swamp boat. We could see blue sky just a few feet higher than the ground blizzard, but we could not see the flags.
After we spent about 10 minutes watching the blowing snow, the winds let up enough to restore visibility. We turned onto Cape Evans Road and headed northward. We crossed Backhoe Crack at the marked crossing, and soon headed into a region with a lot of rafted ice. Rafted ice is created when the sea ice breaks up into floes and the ice floes refreeze in a jumble. Pieces of ice along the edges of the floes stick up at odd angles. This all happened over winter; though it is safe for travel now, it makes for a very bumpy ride! We bumped our way along in the Pisten Bully and finally saw the turn for Turtle Rock. Turtle Rock is a tiny little island nestled against Ross Island, north of McMurdo Station. Because Turtle Rock sticks up out of otherwise uninterrupted sea ice, it produces pressure on the surrounding ice. (Turtle Rock doesn’t move when the ice expands and presses on it.) The ice relieves this pressure by cracking around Turtle Rock. This makes it a good place for the seals to haul out, because these cracks create reliable breathing holes.
Today, there were seven seals hauled out next to Turtle Rock; three of them were definitely male, and the others were likely males also. Several of them were covered with ice and snow! At least a few were probably hauled out to heal, as they had evidence of wounds that were most likely caused by aggression from other males. Interestingly, male Weddell seals maintain their territories underwater and fight one another underneath the ice. Once they have hauled out, there is an unwritten truce. Seals usually need to haul out to heal because they do not perfuse (send blood to) their skin when they are underwater. If they did send blood to their skin, they would lose heat too fast because water is very conductive. So they have to wait until they haul out to warm up their skin; this is when the healing process can happen.
The future moms were not out yet, but we were not concerned. Because they do not eat during the first weeks after giving birth, Weddell seal moms tend to forage intensely right before they haul out for pupping. The earliest pups are usually born around October 12th, so we expect the moms to stay out feeding for a little while longer. What we did see was evidence that the males are beginning to establish their underwater territories near Turtle Rock. The breeding season is about to begin!
Written by: Heather Liwanag