Despite a slow start to the field season, we kept ourselves occupied with various outdoor survival trainings and gear prepping in the lab.  While we were hoping to deploy tags soon after our arrival in Antarctica, this delay was a welcomed event while we patiently waited for the Weddell seals to complete their annual molt.  However, as more time passed, we realized that we would have a lot of work ahead of us in order to deploy all 22 tags in the time remaining.

On the 25th of January, we deployed our first tag on a large molted female Weddell seal.  During the following 16 days, we deployed the remaining 21 tags.  Due to the logistical difficulty of reaching some of the areas via helicopter, we often tagged two or three animals in a given day.  With each procedure lasting 2 hours and with very few days off, I am confident that I have never felt so exhausted.  The cold temperatures (often 25 degrees below freezing) created additional difficulties in the field; needles freezing instantaneously, batteries ceasing, epoxy not setting adequately.  Even the smallest actions must be meticulously planned – this means keeping batteries, needles, hand warmers, and epoxy containers near the skin to keep them warm and operational.

While the first tag deployment was a learning experience for everyone in the research team, each procedure thereafter was completed more efficiently.  Before long, everyone settled into a niche (anesthetizing, gluing, measuring, collecting samples) and worked as a single unit.

Each day and each animal was different.  Because the helicopters were only going to be operational for another couple weeks, we put our team on the flight schedule everyday for an entire week with the assumption that weather days would give us a well needed break.  Despite below freezing temperatures, weather was not a factor for flying so we set out to tag seals for five consecutive days.  Helicopter trips usually involved a two hour (one way) flight to reach one of our several tagging locations.  Upon finding a suitable landing site, we loaded several hundred pounds of gear onto small sleds which we then towed approximately a quarter mile to reach the seals.

Each seal responded differently to anesthesia and had to be dealt with accordingly.  Once anesthetized, we collected blood samples and injected Evan’s Blue dye and tritium into the animal to determine blood volume and body composition.  Next, we measured the length and girth of the animal and then collected ultrasound measurements of blubber thickness.  While two people used 5 minute epoxy to attach the CTD tag to the head and the VHF tag to the back of the animal, two other people worked to collect several physiological samples such as blubber and muscle.  Because blood samples needed to be collected every half hour for two hours in order to adequately determine body composition, we took the opportunity to weigh and flipper tag each animal during the measuring intervals.

After spending anywhere from 4 to 8 hours tagging seals in the freezing cold, we lugged our gear back to the helicopter and prepared for the long flight back to McMurdo station. On a typical day, the crew took an hour break for dinner and then headed to the lab to process samples and to prep gear for the next day.

On February 10th, we deployed the remaining two tags and called an official end to the field season.  However, our next mission will be to recover the CTD tags from the animals.  In order to do this, the research team will return in October (before the annual molt) and attempt to relocate the animals using VHF receivers. Obtaining the CTD tag will allow us to access any additional data that was not relayed via satellite due to limitations in data transfer.

To date, all but one tag is transmitting data!  Overall, this was an incredibly successful field season with much more still to come!