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Monday, September 15, 2008

Residents vs. Transients

A transient surfaces in front of Mt. Baker in San Juan Channel

Yesterday there were no fewer than five separate orca sightings:
  • J and K Pods came down Boundary Pass in the morning, then went up Swanson Channel
  • The L2s were seen off of Kellett Bluffs
  • The T30s were near Hein Bank
  • Another group of L-Pod (including the L55s and L47s) was seen in San Juan Channel
  • The T19s (T18, T19, T19B, and T19C) were also in San Juan Channel
  • A third group of L-Pod wasn't spotted but was probably around, since they showed up off Lopez this afternoon

The most interesting sighting, and the one we got to witness in the afternoon on the Western Prince, was having both residents and transients in San Juan Channel. When we arrived "on scene" with the 4 transients, the L-Pod whales were a good 3 miles north of there. We watched as the transients made a kill, then started moving northward. Slowly, the gap started to close, and it became apparent the whales were going to be close enough that an interaction was possible. Normally (if there is such a thing as normal when it comes to whales), residents and transients simply avoid each other. They are not known to interact whatsoever, and genetic tests indicate they may not have interbred for more than 10,000 years. In the handful of documented resident/transient interactions, the residents have seemingly chased the transients away from the area. The hypothesis is that the marine mammal feeding transients may at times pose a threat as a predator to the fish eating residents, particularly to young calves.

The T19s in San Juan Channel, following behind the residents

Before long the residents and transients were within 1/2 mile of each other and we could see both groups of whales. The residents were in the lead, traveling north in a very tight group very close to shore. They were definitely behaving differently, all surfacing together and going on longer dives than normal (there's that word again). The transients were following behind, also close to shore, and kept on traveling steadily for a good 15 minutes or so. An interesting note is that all the residents were females and juveniles; there were no adult males in the group. Does this mean the transients posed more of a threat? The Ts were definitely still outnumbered with 4 of them to more than a dozen residents.

The residents surfacing all together in San Juan Channel, traveling about 1/2 mile in front of the transients.

In the end, the transients drifted back and ended up circling Yellow Island, where they made another kill. The residents continued on their way. We saw no evidence of a direct interaction, but they were close enough to each other that both groups certainly knew the other group was there. Were the residents acting differently because of the transients? We will never know for sure, especially because the residents were acting strangely anyway by being in San Juan Channel in the first place, and by being an odd assortment of L-Pod whales to be seen apart from the rest of the pod. Still, it was exhilarating and bizarre to see both types of killer whales so close together, and if anything just added to the list of all the mysterious things we don't understand about these fascinating animals.

1 comment:

The K said...

Simple question: Is there a convenient on-line map that shows the places you mention, e.g., Boundary Pass, San Juan Channel, Kellett Bluffs, Hein Bank? I'm not an Islander and probably only know 3 or 4 of the main island by name. The places you mention don't lend themselves to finding on google maps or even google earth (my main place resource) so I have no idea where they are.