During the second half of the pupping season the field team conducts surveys of all the Weddell seals in the study area with a goal of completing 6 surveys per year. This allows the project to encounter each seal in the study area on at least one of their surveys. Weddell seal survey days are long ones for the field team. The team will cover the Erebus Bay study area, and identify and record every seal encountered during that single sweep. To accomplish this, the team will travel by snowmobile to the all different southerly Erebus Bay pupping colonies, and move quickly through those colonies to record every seal they come across. And they will travel by helicopter and on foot to cover the northerly Erebus Bay Weddell seal colonies during this unusual 2025 field season.
This survey information is recorded in both small field books the researchers carry and on the hardy handheld field tablets they now use on the ice. Back at McMurdo Station after the survey, data entered into the field books will be compared with the data entered into the field tablet computers to ensure accuracy of the count. Lead scientist Prof. Jay Rotella notes, “For each seal observation, we record the date, location, seal tag numbers, sex, age class. For females with pups, we also record that they are a pair.”
Since Weddell seals spend a good amount of time in the water under the ice, they may not be visible to the team when it moves through an area on a particular occasion. To address this, approximately 6 full surveys will be conducted over the pupping season. This makes it more likely that the researchers will encounter every seal in the study area at some point during the survey period, and so achieve an accurate count of the entire Weddell seal population in the study area for the current season.
Project founder and former Co-PI Prof. Emeritus Don Siniff writes in an unpublished manuscript on the history of the Weddell population project that, “In 1973 the decision was made to tag all the pups born into the McMurdo population as well as a significant number of adult females.”
“When the effort to tag all the pups born into the McMurdo population was initiated an effort to walk through the pupping colonies and record all the individuals present, along with the tag numbers, was begun.”
“Initially, data from these census undertakings were recorded in a standard field notebook,” Siniff explains, and that practice continues to this day. “In the mid 1980s, small handheld computers became available. This started a process of developing a data entry system that could be used to record tag numbers and the other data as we moved through the pupping colonies.”
“Ward Testa was instrumental in this development at this time, and wrote the first data entry program which contained routines that checked each entry as it was entered to make sure the new data were consistent with what was already in the data base. This data checking routine proved extremely valuable in limiting the number of mistakes entered into the data base.”
“In 2002 the project moved to Montana State University with Drs. Jay Rotella and Bob Garrott as lead principal investigators. The data entry program was rewritten by the Montana State University program in order to take advantage of the upgrades in handheld computers and bring the data entry software up to date.”
Notes Siniff, “The database now consists of perhaps the most complete record on marked individuals that have been seen repeatedly over their lifetimes. These data can now be subjected to advanced statistical analyses, using the latest programs and models that make up a major area of study focusing on multiple mark-recapture data. A number of population statistics can be accurately estimated from such analyses, including the investigation of ecosystem measures whose influence on the dynamics of the Weddell population can now be explored in detail.”
Learn more about the Weddell seal population study at WeddellSealScience.com.
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