Unexpected Cetacean Sightings in Puget Sound

The Ways of Whales workshop last weekend included a lecture by John Calambokidis, one of the co-founders of Cascadia Research and a local cetacean expert. One of the things he talked about was a series of bizarre whale and dolphin sightings that have occurred over the last year in Puget Sound. 

In January 2010 a dead Bryde's whale was found in Puget Sound after there had been several reported sightings of an unusual (live) whale in the region. Bryde's whales are medium-sized (relative to other whales, that is) baleen whales that are found in tropical waters. In the United States, they usually aren't found north of southern California. After conducting a necropsy, it was determined that while the whale had some evidence of propeller wounds and rope entanglement, neither of these were the apparent cause of death. Instead, due to the empty stomach and thin blubber layer, it was hypothesized that starvation may have played a role. This was the first-ever sighting of Bryde's whale in the Pacific Northwest.

The story got stranger when another live Bryde's whale was found in Puget Sound in November 2010. This animal had severe injuries along its back from a ship strike, and Calambokidis expressed that he thought it was amazing the animal had survived at all, as the most severe of the multiple injuries had actually severed off the tops of multiple vertebrae. He estimated the injuries had occurred about a month prior. Unfortunately in December 2010 this whale also died, succumbing to his injuries.

There have also been sightings of two members of another unexpected species in local waters - the bottlenose dolphin. The only previous record of a bottlenose dolphin in the Pacific Northwest goes back to a dead animal that was found in the late 1980s. The first live sighting occurred in June 2010, of an animal that was seen multiple times before it stranded in July. Then a second bottlenose appeared in December 2010, and was seen alive on numerous occasions up through January 18th, before it too was found dead. Bottlenose dolphins also tend to be a more tropical species, usually not occurring north of southern California, though they have seen as far north as San Francisco in the last 30 years.

There are anomalies in nature, so when I first heard about these sightings I figured they were wayward animals, probably sick or injured which led them to deviate from their normal range. Once you have four tropical animals showing up well out of their range within a single calendar year, however, you start to wonder....is this part of some greater trend?

The instinct right away is to point to climate change and shifting ocean temperatures, but there have been no greater trends established about altered cetacean ranges. Most animals are still sticking to where they're expected to be found. Also, we're in the middle of a La Niiña cycle, which makes for cooler, not warmer, water temperatures.

Scientists involved aren't offering any explanation for the multiple unusual sightings, but it will be interesting to see if more tropical cetaceans are sighted throughout the rest of 2011.