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Weddell Seal Pupping Season--
Adding to a Unique Marine Mammal Data Set
This Weddell seal population study, initiated by Don Siniff in the late 1960s, is one of the longer running animal population studies, and the longest marine mammal population study in the southern hemisphere.
One of the benefits of such a long-running study is the extensive database built up over the decades on this population of Weddell seals in the Erebus Bay area of Antarctica's Ross Sea.
Because of this unique data set, Montana State University Weddell seal project scientists were well positioned to study the effects of a massive iceberg event in the past decade that blocked the seals' access to many of their usual pupping colony locations in the Erebus Bay study area.
Findings of project scientists were published Sept. 26, 2012 in the international journal, Proceedings of the Royal Society B: Biological Sciences. Lead author of the paper is Thierry Chambert, then a doctoral student supervised by Jay Rotella in the MSU ecology department. Jay Rotella and Bob Garrott are co-authors on the paper, and are Co-Principal Investigators on the Weddell seal population project with Don Siniff.
- Mary Lynn Price Adapted and Expanded Blog Post, 09 October 2012
Tagging Weddell Seals - Project's Long History of Recording Generations of Weddells
Now in high gear, the Weddell seal population study field team is setting up their remote sea ice camp, continuing to flag safe routes over the sea ice to the various pupping colonies, and tagging new pups born this season in the Erebus Bay study area.
The field team will also be conducting a series of census surveys of the entire Weddell seal population in the Erebus Bay study area to determine how many seals are present this season. Efforts to weight a select number of pups and moms for the project's mass dynamics study will be limited this season, however, because of the shortened time that the team will have on the ice during the critical period of the pupping season due to the government shutdown and field season delay.
The tagging of Weddell seals is central to this long-running population study. This season, the primary focus of the field team will be tagging all of the newborn pups in the study area. Previously untagged Weddell moms are also tagged, and seals with broken or misssing tags are retagged.
Tagging Weddell seals has been part of this project since its very beginning. The history of this project began with the initial tagging efforts of Dr. Ian Stirling in 1963, which were continued byDr. Don Siniff and others from the University of Minnesota beginning in 1968.
The photo above is from 1973. From left to right in the top row are Don Siniff, Bob Hofman, Doug DeMaster, Dick Reichle, and kneeling from left to right are Ron Kirby and Ian Stirling. All of these individuals have gone on to have successful careers in various fields of ecology. Photo courtesy Don Siniff's Weddell project archive.
In 2002, the Weddell project moved to Montana State University with Drs. Jay Rotella and Bob Garrott as Co-Principal Investigators, along with Dr. Don Siniff (Professor Emeritus, University of Minnesota) who has continued as Co-Principal Investigator on the project. Bob Garrott initially worked on the project as a graduate student of Don Siniff, then would go on to become a Principal Investigator on the project some years later. So this long-term population project represents not only multiple generations of Weddell seals, but also generations of ecologists! For much more on the history of the Erebus Bay Weddell seal population study, please visit our WeddellSealScience.com History section.
Over the decades, a variety of different shapes and sizes of tags have been used in the Weddell seal population project, the most recent tag being the small plastic cyan-colored tag seen in the lower right hand of the photo below. More historical info on these tags is available as part of the Weddell seal database download available here.
The purpose of tagging these Weddell seals is to establish and record the birth date, birth location, gender, and identity of the mother of a newborn seal using a small plastic uniquely numbered tag that is affixed to the rear flipper of the seal. This information is recorded in the extensive database maintained by the B-009 population study since 1969. Data are available for download here. To date, approximately 23,171 Weddell seals have been identified and tagged over the life of this study in the Erebus Bay area.
Weddell seals are "philopatric", meaning they show strong fidelity to the areas of their birth, returning to these same areas to give birth themselves. This life history characteristic is what allows the scientists to develop extended reproductive histories of thousands of Weddell females. The researchers know when these seals were born, where they were born, how many pups they have had over their lifetimes and, in many cases, whether those pups survived to have pups of their own.
Because Weddell seals are long-lived mammals and don't start to reproduce until they are around 7 years old, this kind of extremely valuable multi-generation database requires decades to develop. Here's a brief project video about studying Weddell seals...
- Mary Lynn Price Adapted and Expanded Blog Post, 30 October 2013
Making it Count - Weddell Seal Surveys Underway
Weddell seal survey days are long ones for the field team. The team will cover the entire Erebus Bay study area in one 24 hour period to count, identify, and record every seal encountered during that single sweep. To accomplish this, the team will travel by snowmobile to the all different Erebus Bay pupping colonies, and move quickly through those colonies to record every seal they come across.
This survey information is recorded in both the small field books the researchers carry and the hardy handheld field computers they use on the ice. Back in camp after the survey, data entered into the field books will be compared with the data entered into the field computers to ensure accuracy of the count. Lead scientist 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. For a subsample, we also collect a very small tissue sample for genetics work and record that. If we weigh the seal or outfit it with a swim tag, we also record that information."
Since Weddell seals spend a good amount of time in the water, they may not be visible to the team when it moves through an area on a particular occasion. To address this, 6 to 8 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.
Co-PI 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. These 'census' efforts were generally repeated at least seven times each pupping season and the census tallies became the central part of the growing database."
"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."
More work on improving the field computers was done by Michael Cameron, who worked as a PhD student with Don Siniff on the Weddell project for a number of seasons. Siniff notes, "In the late 1990s Michael Cameron contributed significant upgrades to what Ward Testa had developed, and we purchased new field computers as they came on the market. This was essential as the database was continually increasing in size and the data checking programs needed additional computer storage space and increased speed.”
"In 2002 the project moved to Montana State University with 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. Since its arrival at MSU, the database has been subjected to analyses taking advantage of the fact that the McMurdo population database currently consists of over 80 percent known-age individuals.”
This season, the team is using a new field computer called the Trimble Ranger 3, shown in the photo below, which includes GPS capability.
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."
-Mary Lynn Price
Adapted from a Field Blog Post 13 November 2013
Weddell Pups: Weighing In
Weddell seal pup mass (weight) at weaning is important to seal survival, and is an essential measure of maternal investment by Weddell moms in their pups. Weddell moms usually fast during the 5 to 6 week nursing period. And for every pound a pup gains during the nursing period, the mother can lose around 2 lbs of her own body mass. Weddell pups can more than triple their birth weight before being weaned, so there is a very large transfer of energy from mom to pup during this nursing period.
The Weddell seal population and mass dynamics project has published a number of research papers to date on Weddell seal reproductive costs and the relationship of pup mass to seal survival. The researchers continue to learn more every year about this long- lived apex predator and how it interacts with its changing Antarctic environment.
A crucial part of the Weddell seal research team's field work involves weighing pups at 3 different stages during the 5 to 6 week nursing period, with the first weighing taking place a day after birth, a second weighing around the mid-nursing period at 20 days, and a third weighing near weaning at around 35 days. The 35 day pup weights range from around 150 to 280 lbs (68 to 127 kg). In the images below, field researchers weigh a large pup as the mom looks on.
Also during the 35 day weighing, researchers will retrieve temperature tags from those pups that received the small temperature sensor/recorders. "Out of the 57 temperature tags we deployed on pups this year, we have successfully recovered 16 so far. We know that three of the tags have been lost, so we are crossing our fingers for getting the remaining 38 by the end of the season," says field researcher Jesse DeVoe.
In the image above, data from one of the small temperature recorders is displayed in graph form. Because sea water temperature under the ice is a constant -1.8° C (28° F) but the surface temperatures on top of the sea ice can vary widely, researchers are able to determine when pups are in the water based on the data recorded by the temperature tags. DeVoe notes, "The data retrieved so far shows lots of swimming pups!"
- Mary Lynn Price Adapted from a Field Blog Article 23 November 2011
Weddell Pups Learning To Swim
Weddell seal field research team member Jesse DeVoe was there with his camera to get some wonderful new video of a mom and pup in a small swim hole. The Weddell mom is enlarging the hole with her teeth to make the pup's entry and exit into the water easier, and encouraging her new pup to join her for a swim.
Weddell moms take an active role in nurturing their pups during the nursing period, and helping them learn to get in and out of the water through the cracks and holes in the sea ice as they learn to swim. Weddell pups usually begin swimming when they are approximately 1 to 2 weeks old.
Some of the new pups will receive small temporary temperature recording tags so that the research team can record how often they swim and for how long during the nursing period. Here's one of our project videos about Weddell pup swimming activity and the temperature tag project: "Are Some Weddell Seal Pups Couch Potatoes?"
- Mary Lynn Price
From a Field Blog Entry 29 October 2012
These Articles Have Been Adapted From Select Antarctica Field Blog Posts
Created Over the Years During the Weddell Seal Pupping Season. The Entire Weddell Seal Science Field Blog Can Be Found Here. Return to Main Select Articles Page