We are pleased to announce that a new scientific paper produced by our team has just been published. The paper compares birth dates for pups born to mothers that were also born in the Erebus Bay study area with birth dates for pups born to mothers that come into the Erebus Bay population from elsewhere.

The Erebus Bay population of Weddell seals is the southernmost mammal population in the world, and birth-date synchrony has been demonstrated in this population. Reproductive synchrony is thought to occur because the timing of when pups are born is important to offspring survival in strongly seasonal Antarctic environments. One can imagine that being born too early in the year could expose pups to severe weather in late winter and early spring. Being born too late might increase the chance that a pup might encounter killer whales (Orca) while still developing swimming and diving skills when the ice breaks up in late spring and early summer.

All prior work on birth timing in the Erebus Bay population has been done on pups born to locally born mothers. However, many mothers in the population arrive from areas to the north of Erebus Bay where the timing of breeding might occur earlier and cause pups to be born earlier. The new paper analyzed birth dates from more than 7,500 pups born to more than 2,200 mothers in 22 different years and found that there were no biologically impactful differences in the birth dates of pups born to locally born mothers as compared to those born to mothers from more northerly sites. Given that mothers that originate outside of Erebus Bay now commonly make up 40% of all the mothers in the population, it is helpful to know that their birth timing is similar to that of locally born mothers. It will be interesting in the future to compare the survival rates of pups born to different types of mothers.

The new paper highlights several aspects of the project. First, the long-term nature of the project along with the intensive study of individuals year after year allows the project to collect and analyze large amounts of detailed data over many years. For example, because all pups born in the study area have been tagged for many decades and because visits are typically made to each colony every 2-3 days, it’s possible to know when most pups are born and to know a lot of detail about their mothers.

In addition, the paper also highlights the role that the project plays in training the next generation of ecologists. Abram Brown, who is the senior author on the paper, graduated from the Ecology Department at Montana State University in Spring of 2023 and joined our field team as a research technician in 2023 and 2024. During the 2024 season, Abram expressed an interest in the question that is at the heart of the paper. During some days when bad weather had our team indoors in Fall of 2024, Abram worked with the second author, Parker Levinson, a Ph.D. student on the project and our field crew leader, and Jay Rotella, the project’s Principal Investigator, to hone the question, prepare the data, and begin analyses. Abram then worked on reviewing the literature on the topic, conducted formal analyses, and wrote the paper along with Parker and Jay.

Abram’s scientific curiosity combined with the long-term database from the project, analysis skills, careful writing, and rounds of editing led to the paper being submitted to the journal Antarctic Science, where it was reviewed and eventually accepted and published. It’s really rewarding that we were able to learn more about Weddell seals while training one of our research technicians on the process of writing a scientific paper in the midst of conducting field work. Also, it was great for Parker to gain experience mentoring Abram who was then beginning to apply to graduate school and was recently accepted into a Ph.D. position at the University of Washington. It’s great to see the project gain and share knowledge, point out new questions for the future, and continue to train new people in a variety of new skills. Thanks to all involved in collecting the data and supporting our project. It definitely is a team effort.

– Prof. Jay Rotella, Principal Investigator
Erebus Bay Weddell Seal Population Study