8 November, 2003
Today was census day. No, we didn't go door-to-door quizzing our seal neighbors about their professions, income levels, or buying habits. Instead, we spent the day visiting each of the seal colonies in our study area and counting all the tagged and untagged seals that we saw. This was the first of 8 censuses we will conduct over the next few weeks to gather data about population numbers and composition that can be analyzed to determine survivorship rates and population demographics for the seal colonies.
The logistics of the census are straightforward. The study area was divided into three sections: northern (Cape Evans to North Base), southern (Pram Point to South Base), and the Delbridge Islands (Big and Little Razorback, Inaccessible Island, and Tent Island). We worked in teams of 2-each pair was assigned a specific section to inventory. Our mission was to visit each colony within our section as well as to survey the areas in-between colonies to look for errant seals. At the colonies we checked each seal and noted its age class (adult or pup), gender, tag number (if it was tagged), and any relatives it had (like a mother and her pup) entering the information into both our notebooks and our field computers. Kelly and I had the northern section, Gillian and Mark the southern, and Darren and Brent took the Delbridge Islands. When we do our second census next week, one person from each pair will rotate to one of the others while the other does a second census of the same section, so that there is some consistency between censuses. In addition, we will change the order in which we survey the colonies. For example, today we went in a counterclockwise direction, starting at Cape Evans and moving south towards North Base, next week the census will start at North Base and work towards Cape Evans.
While counting seals may sound fairly easy, there's a little more to the whole process. First, it is sometimes hard to read the flipper tags on some of the older seals. The numbers may be faded, or the tag is hidden in the flipper's folds. It then becomes a matter of who tires first-the seal or the researcher-as you walk behind the seal trying to lift the flipper to read the tag while the seal pulls in the flipper and does a kind of slide/shuffle on the ice to stay just ahead of you. So you spend a fair bit of time walking in circles playing a game of 'follow the flipper'. In addition, some mothers like to cover their pup's flippers when we approach to read the tag number. When the moms are protective it also makes it hard to hold onto the pup long enough to flip it over on its back to figure out its sex. Then there's the tags-there are different color tags on some of the seals. These colors fade with time, so that a tag that was originally violet now looks kind of reddish, or ones that were light yellow have faded to a white sort of color. We each carry a string of tags so that we can match the colors and figure out the proper color. Last but not least, some seals are just plain difficult to reach or find as they may lie on the far side of a large meltwater pool or hidden behind blocks of ice pushed up along a pressure ridge.
By day's end, we had counted 978 seals, including all tagged and untagged animals. We will do the next census on Wednesday. Before then, we will be out tagging the pups and females that we saw today who were untagged and tagging any new pups that are born before the next census.
Counting all the seals
Do you have a flipper tag?
Hold still while I look
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