Gray Seal Pup Sampling on Monomoy Island

Posted on February 27, 2018


Ashley Stokes | SSC Marine Mammal Rescue Manager

Monomoy Point Light

Monomoy Island, off of Chatham Massachusetts, is a known rookery and birthing site for gray seals. Gray seals are the larger, more aggressive relatives of the harbor seal that is typically seen up here in New Hampshire. From January 13-16th, Sarah and I teamed up with 13 other biologists on an annual seal sampling excursion, led by a biologist and research scientist from MIT.

Let me put this excursion into perspective. See the top photo? That is where we stayed. There was no electricity, no heat, no running water, and basically no furniture or cooking amenities to speak of! A little daunting nonetheless, but it was too exciting and interesting of an opportunity to pass up.

What are they sampling for? The answer is very complex, but some of the things they are looking into include: influenza, phocine herpes virus, phocine distemper virus, antimicrobial resistance, contaminants (mercury, PCBs, etc), and overall baseline data for what a healthy gray seal pup is typically like. Daylight hours are spent out in the field on the island collecting and sampling gray seal pups that are weaned from their mothers and the evening hours are spent inventorying and processing the many samples that were taken for each animal.

Each animal takes about 30 minutes start to finish and you might think, “that’s not so bad…seal pups are small!” The harbor seal weanlings we are used to seeing, are about 20-25 pounds and generally pretty docile. The gray seal weanlings that we sampled were between 61-106 pounds and are extremely aggressive! At times, I thought I was taking part in a rodeo. For each animal, the process generally goes like this: (1) The field sample station, data sheets, and scale are set up before the animal is approached, (2) Photo and lat/long of the animal is taken before it is collected, (3) Two people move in on the animal and collect it in a collection bag, (4) Animal is carried to the sampling area and weighed, (5) Animal is released from the bag and restrained on the ground, (6) blood samples are collected and subsamples of the collected blood are performed in the field, (7) nasal, ocular, and rectal swabs are collected, (8) lanugo fur if present is collected, (9) a whisker is collected, (10) two biopsy punches are taken from the hind flipper for genetics testing, (11) the animal is flipper tagged and marked with a paint stick, morphometrics (level A measurements) are taken, (12) the animal is rebagged and returned to its original collection location. Then we set back up for the next animal and repeat the process!

Overall, it was an exhausting week, but we wouldn’t have traded it for anything. The knowledge, sampling experience, and networking that we gained was truly amazing. We were even able to view many adult seals, mother seals with their newborn pups, and even a snowy owl! We are extremely cautious and aware to give all adult seals and newborn pups a very wide birth and to never disturb them.


Gray Seal Pup
Gray Seal After Sampling
Snowy Owl
Our Sampling Group

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