The field research team now has internet at the remote sea ice camp! They report that they have tagged over 49 new pups around the study area. The rate of pup births will continue to rise over the next few weeks as more and more moms will be arriving at the pupping colonies and giving birth.
In these photos (above) by Ph.D. student Terrill Paterson we see members of the field team approaching a mom/pup pair to weigh and tag a new pup. Terrill is lead author on a recent new Weddell seal project scientific paper on pup birth dates, age of moms, pup weight at birth and at weaning:
|Paterson, J.T., J.J Rotella, J.M. Mannas, and R.A. Garrott.2016. Patterns of age-related change in reproductive effort differ in the prenatal and postnatal periods in a long-lived mammal. J. Animal Ecology - DOI: 10.1111/1365-2656.12577.|
Dr. Jay Rotella is lead author on another recent scientific paper on variation of pup birth dates and extreme climatic events:
|Rotella, J.J., J.T. Paterson, and R.A. Garrott. 2016. Birth dates vary with fixed and dynamic maternal features, offspring sex, and extreme climatic events in a high-latitude marine mammal. Ecology & Evolution Online Early View - http://dx.doi.org/10.1002/ece3.1985|
Many more scientific publications by the Weddell seal population study scientists can be accessed on our outreach web portal's Publications page.
What the scientists have found using several decades of data on these seals is that pup birth dates and mass vary based on the Weddell mom's age. Dr. Jay Rotella reports that there is substantial individual variation in pup birth dates, pup birth weight, and pup weight near weaning related to the mom's age:
1) at birth, prime age mothers weigh more than younger or older moms,
2) young and old mothers typically give birth to lighter pups than prime-age moms,
3) pups with young moms gain weight at a lower daily rate than do pups with older moms (prime or old), and this is true for both the first 15 days of lactation and for later on in lactation,
4) pups with moms in the oldest age class gain weight at the highest rates, which allows them to catch up to, and perhaps pass, the late-lactation mass of pups from prime-age moms
5) in total, these results suggest that older mothers are either
a) allocating more of their energy to their pups (assuming they don’t feed anymore than others) and so taking a bigger hit in terms of mass loss (both total weight loss and % weight loss) and/or
b) feeding more than other mothers
c) … it is possible (but seems unlikely to us) that they are more efficient at transferring mass (nursing efficiency, energy transfer, etc)
6) annual variation in these results is very minor
7) individual variation is quite large and there’s good evidence that individuals have repeatable performance through life where some females repeatedly produce bigger (or smaller) pups than do other mothers who are similar in age, breeding experience, etc.
8) these results are now leading us to develop 3D imagery methods that will allow us to estimate weight changes in mothers throughout the season.
Covered snowmobiles parked in front of the kitchen hut on the sea ice ready for the day's work ahead can be seen in this beautiful black & white photo by Ph.D. student and field team member Jamie Brusa.
- Mary Lynn Price