Chiswell Chronicles: June 12, 2017

Since 1998, scientists at the ASLC have been monitoring the behavior and population dynamics of Steller sea lions (SSLs) at a rookery in the Gulf of Alaska: Chiswell Island. Rookeries are where sea lions go each summer to give birth and breed, so observing the dynamics and behavior at these locations can provide critical information about the factors affecting populations. This is particularly important in the Gulf of Alaska where the Western Distinct Population Segment (WDPS) of Steller sea lions is still listed as endangered.

Using remotely controlled cameras, our crew starts their day at first light (in the Alaskan summer that can be as early as 4:00am!). Throughout the day, we record which animals are on the island, track the animals’ behaviors, and note when new pups are born.

We are a few weeks into the breeding season now. The first pup was born on May 23rdand there are now 42 pups total! On average, at least 10 new females are still arriving every week, so we anticipate more pups to come!

Females, pups, and a large male resting in a tide pool on Chiswell Island.


One unique aspect of this work is that individual Steller sea lions can be identified by their natural markings (e.g. fungal patches, scars, flippers). This enables us to track known females over multiple years.

This week, a female named Melon arrived on Chiswell. We first saw her in 2006! She has returned to Chiswell every year since, and just gave birth to a pup last night.

Melon is a female Steller sea lion. Researchers can identify her by a round, dark, fungal patch on her right flank and by a notch on her left flipper.

Stay tuned throughout the summer for more updates on pup numbers, and to learn about more of the female SSLs that come to Chiswell Island!

All photographs and activities conducted under NMFS Permit No. 18438-00

Written by: Dr. Amy Bishop and Pam Parker

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