Monday, August 02, 2010

Whale Town

Last week the clouds lifted for a few days allowing us a glimpse of life off the island. Not only could we see civilization on the mainland, but other marine life was suddenly visible. The most prominant visitors we had were the Humpback Whales.
Two Humpbacks near the Farallones

These whales are well known for their acrobatic aerial displays (breaching) where they jump, and often spin, out of the water. Although the function of this behavior is not known, it is thought to possibly be involved in communication and/or ectoparisite removal. In any case, it's always incredible to watch. From the island, we have seen numerous whales breaching, tail slapping and flipper slapping. Our high count of Humpbacks last week was 91 in a single day! The number of Humpbacks observed from the island varies significantly from year to year but in the last two years we have seen very high numbers here in the late summer and fall. The high count last year was 107 on Oct 8, the second most seen in a single day (highest count was 125 on November 8 1998). It is definitely unusual to see numbers this high already in August so we may still break the record.

Humpback Whale showing how it got its name

 
Humpbacks weren't the only cetacean species spotted from the island last week. We also saw Risso's dolphins, Northern Right Whale Dolphins, Gray Whales and Blue Whales.
Risso's Dolphins near the Farallones
Blue Whales are the largest animal to have ever lived on this earth and were once extensively harvested. PRBO began recording recording cetacean sightings from the Farallones in 1973, only a few years after whales became protected in the US. The first Blue Whale was not seen from the island until 1978 and our counts since then have documented an increasing number of whales present in this area. Our high count last week was 7 in one day!

Blue Whale back. It's hard to get a feel for how big there are from this.

Although its always a treat to see whales, seeing them in these numbers is especially thrilling. Humpbacks were hunted extensively in the early part of last century, down to perhaps as few as 1400 animals in the North Pacific. Once whales became protected, Humpbacks and other species began to recover. Currently, the North Pacific population is estimated to be closer to 20,000 with around 1200 of those in the California/Oregon/Washington Stock (http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/humpbackwhale.htm). Counts recorded from the Farallones have helped to document the increase in the Humpback population as well as other species of cetaceans.


Cassin's Auklet chicks are fed krill by their parents
The presence of this many whales is yet another indication that there is a lot of krill around. Humpbacks and Blue Whales are baleen whales which means they filter large amounts of water to gather up their small prey. Humpbacks tend to eat a variety of small prey including krill and small fish, but Blue Whales feed almost exclusively on krill. They are the Cassin's Auklet of whales. The only difference is they are about 3000 times the size of a Cassin's Auklet! The presence of Blue whales, and the fact that Cassin's Auklets are producing lots of fat, healthy chicks, indicates the high abundance of krill in the vicinity of the island.







Happy as the whale recovery stories are, significant threats to whales remain. We witnessed one of the most serious last week when we found a dead Humpback floating near the island that appeared to have been struck by a ship. There were numerous deep lacerations on the whales left side. As this incident demonstrates, ship strikes are still all too common and remain a serious concern and cause of mortality to many whales.

Dead humpback spotted near the islands
Lacerations on the left side of the whale likely from a ship propeller

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