April 30, 2016

Rosario Rendezvous: T65As Killer Whales Hunt in Rosario Strait

Transient Killer Whales near Orcas Island

What do you think about when you think about sound? Maybe you think about music, or birds, or waves crashing, but I bet you think about all of those sounds going into your ears right? We hear sounds all the time, even when we’re sleeping, but imagine a world that you experience almost everything through sound. This the world of dolphins, and especially the largest species of dolphin, the orca. Orcas echolocate. This is how they mainly interact with their watery world and it kind of works like sonar. They produce sound with unique features in their blowholes, then direct that sound through their melons located on their forehead. The sounds bounce off objects in the water, boats, fish, rocks, seals, anything and everything then return to the orca, but not in the way that you would expect. The sound waves travel through the orca’s lower jaw and into the inner ear. This is because the ears are closed up, which may be a good thing. Imagine having a wicked case of swimmer’s ear your entire life. Once in the inner ear the sound gets transformed into nerve impulses and is eventually interpreted in the brain to make a 3D map. So cool! But today we were searching for the silent hunters.

Of the two types of orcas that inhabit the waters around the San Juan Islands, the Transient Orcas hunt here throughout the entire year. They are searching for marine mammals, and mostly Harbor Seals. Since they are hunting other intelligent mammals, their technique is going to differ from the fish-eating Residents. They travel in smaller groups, they have several ways of splashing to knock prey off of rocks, and also hunt silently. Instead of using their echolocation abilities to find their prey they quietly do visual scans under water. This is so their prey don’t hear them and reach the relative safety of land before the orcas have a chance to strike. These are the type of orcas we were looking for today.

We first spotted them on the east side of Orcas Island near the Pea Pods. As. we watched they hunted, cornered, and preyed on a few different prey items, aka seals. It was the T65A family group, and they were very silent. Even when they surface to breathe you see very little splashing, and they wait till their blowholes are completely out of the water so their breathing makes the least amount of noise as possible underneath the water. We even through a hydrophone in to see if we could hear them, but not even the sound of splashing or swimming was heard – silent as the grave. They continued to move north through Rosario Strait and it was breath-taking to see them to pop up in the most unexpected places and see the young ones practice deeper dives indicated by the more tail shown.

As we said goodbye to those amazing whales we headed through the outer islands, some of my favorite, of Barnes, Clark, and Sucia to find Steller’s Sea Lions hauled out on the rocks growling at each other. These 10 – 12 ft. giants are sometimes prey to the Transient orcas, but they usually stick to the smaller Harbor Seals. We soon had to head for home again, but not before we finished a whole circumnavigation of Orcas Island!

Whale folks, hope your days have been as sunny as ours. Until next time.

 

Naturalist Erick

M/V Sea Lion

San Juan Safaris