Wildlife Calendar

SEASONS OF THE SEA

Whales and Wildlife of the Farallon Islands

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Winter

Gray Whale Migration:

As Arctic days shorten and the surface ice pack begins to thicken and expand southward in October, pregnant female grays, already well into their 12-month gestation, slip south through Alaska's Unimak Pass and begin their extraordinary annual 6,000-mile journey to Baja California. Non-pregnant females, mature males, and juveniles follow over succeeding weeks. For the expectant females, the voyage is a demanding and determined one. Traveling alone or in groups of two or three, with little rest and seldom pausing to feed, they may travel 20 hours and 100 miles each day in their urgency to reach the protected, subtropical lagoons in which their young are born. For the trailing whales, the journey is no less arduous. They swim in groups of up to 12 animals, and reach Baja in six to eight weeks.

By end-January, most females have reached the near-shore waters and lagoons of Baja California which are their destination. Stragglers continue to arrive for yet another month or more. Off the California coast, the "southern" migration lasts from end November through mid-February while the "northern" migration lasts from mid-February through early June. In February, stragglers are still migrating south while the early returnees are already migrating north.

Farallon Islands:

Pregnant female elephant seals begin arriving in December. The first pup of the season is usually born around Christmas, and pupping peaks in January. Two-ton bulls also return to claim their breeding territories at this time.

Spring/Summer

Gray Whale Migration:

Gray whales migrate northward in two distinct phases or "pulses," the first traveling from December to June, the second from March to July. The earliest returnees are newly-pregnant females, adult males, and juveniles. These whales generally retrace their southward trek, swimming point-to-point across bays and bights, averaging 95-100 days between Baja and Alaska.

Farallon Islands and Gulf of the Farallones:

March ushers in the seabird season, which lasts into August. The Farallon Islands National Wildlife Refuge supports the largest seabird breeding colony south of Alaska. It contains 29% of California's breeding seabirds. Nearly 250,000 birds lay their eggs and raise their young each spring and summer on the Refuge. The most colorful nester the Tufted Puffin arrives, along with thousands of other seabirds, to the Refuge in late March and early April. Twelve nesting seabird species compete for nesting space, vegetative nesting material, partners, and fish to feed their offspring.

June and July are also pupping season for Steller's sea lions. The Refuge and surrounding waters have been designated critical habitat for this endangered species. Northern fur seals were completely eliminated from the Farallon Islands in the 1800s, and just recently (1996) began breeding again on the Refuge. Several pups are born each year in the summer. Although the Farallon Islands are not considered a breeding area for California sea lions and harbor seals, they sometimes pup on the Refuge, especially during warm water years.

In May, the first humpback and blue whales of the season start to arrive along the Continental Shelf and in the Gulf of the Farallones. They come to these waters to feed primarily on krill but humpbacks also feed on schooling fish such as anchovies and sardines. Whale populations were decimated by commercial whaling and many scientists feared that blue whales might have been reduced to the point where they were doomed to extinction. Recent research has revealed that a surprisingly large number of both blue and humpback whales feed on krill in California waters. Humpack whales frequent Gulf and Continental Shelf waters from May through November. Although the concentration of blue whales off California is higher than in any other location in the world, they are seen sporadically in Gulf waters.

Fall

Farallon Islands and Gulf of the Farallones:

From September to November the Farallon Islands are dominated by transient populations of wildlife especially songbirds and other landbirds that occur during fall (and to a lesser extent spring) migration. White sharks, attracted to Farallon waters by the abundant seal population, are most numerous in fall.

Whales are continuing to gorge themselves on food before they begin their migration to their breeding and calving grounds. Most humpbacks appear to migrate to tropical waters off Mexico and south to Costa Rica. (See the California/Costa Rica Connection.)

Gray Whale Migration:

The Chukchi and Bering Seas lie north and south of the narrow straits separating Alaska's Seward Peninsula from the easternmost thrust of Siberia. It is in these sub-polar seas that most gray whales spend their summers, gliding through icy waters rich with nutrients. Unique among whales, they are bottom-feeders, a trait which earned them an earlier nickname: "mussel-digger." Although they occasionally feed on schooling fish or swarming crustaceans, small bottom-dwelling creatures called "amphipods make up the bulk of their diet. Although the total quantity of daily food consumed is not known, it is not uncommon to find ten or more wheelbarrow loads of amphipods in the gray's enormous, three-chambered stomach. The result by summer's end is an accumulation of six to twelve inches of oily blubber, which will be an energy reserve during the winter months of migration to Baja California.

Copyright Oceanic Society Sources:

Oceanic Field Guide to the Gray Whale
Oceanic Society Field Guide to the Humpback Whales
Farallon Islands National Wildlife Refuge, U.S. Fish & Wildlife Service
Cascadia Research Collective

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