To weigh a pup

Pup in: specially-designed duffel bags allow us to roll in and zip up the pups quickly and efficiently to minimize disturbance. One of the benefits of working with Weddell seals is their calm demeanor. There's not very many 1,000+ lbs carnivores that you can walk right up to and don't mind you borrowing their offspring for a moment! It's likely that because Weddell seals are only adapted to ocean-going predators and these maternal colonies don't experience any predators during the pupping season, they don't have any reason to fear two-legged creatures on the ice.

The data collected here is part of our maternal investment study to examine how much mass is transferred to the pup through nursing and what influence this may have on future survival and reproduction of the pups. We only weigh a sample of pups, and only those that are from known-age moms (i.e., we tagged mom when she was a pup in the study area - you can barely see her yellow "alpha" tags in her rear flippers).

Pup up: using a padded pole and a scale bar, two researchers lift the pup off the ice. "147 POUNDS!". This is a 20 day old pup and it already weighs more than me. We weigh them at birth, 20 days old, and 35 days old (approximately weaning). From birth to weaning, they basically quadruple to quintuple their body weight. And ALL of this delivered through nursing. During this time, on average, mom transfers a third of her body weight to the pup. By weaning time, the fairly rotund mom above will be looking quite thin and showing her bony hips. There is little evidence that mom feeds during this period; her observed lethargy by weaning time lends support to this. 

Pup out: Once released from the bag, the pup, with a slightly confused look on its face, quickly reunites itself with mom. It won't be long before pup is resuming normal duties: nursing, swimming, scratching, or sleeping. Researchers here are (left to right) Victor Villalobos, Kaitlin Macdonald, and Shane Petch.