Migration, Feeding and Breeding:
The majority of southbound migrating gray
whales leave the Bering Sea between mid-November and mid-December in groups
somewhat segregated by age, sex and class. They swim along the North American
Pacific coast during the months of November through January or early February.
Some whales do not complete the southbound migrations, instead remaining off
the coasts of British Columbia, Washington, Oregon, or California.
Most of the migrating whales remain close to
the coast, in water less than 100 fathoms (about 600 feet) deep, until
they reach Point Conception, which they typically do between early December
and late January. At Point Conception, where the mainland coast makes a sharp
eastward turn, about 35% of the whales turn to follow the mainland coast,
while the remaining 65% continue directly south, swimming across open waters
toward the northern Channel Islands.
Most whales pass to the west of San Miguel
Island or through the three passes between San Miguel and Santa Rosa islands,
Santa Rosa and Santa Cruz islands, and Santa Cruz and Anacapa islands. Vastly
more of them swim along the western and southern sides of these islands than
along the northern sides.
Whales arrive at Santa Barbara Island from a
variety of directions and pass along either (western/eastern) shore. From
Santa Barbara Island, most head for Santa Catalina Island and pass along the
seaward shore.
Once past the southern Channel Islands (Santa
Catalina and San Clemente), most whales return to the coast. Some whales
continue on into the Sea of Cortes, but most spend their winters in and near
lagoons on the west coast of Baja California and the mainland coast of Mexico
near Yavaros.
It has long been believed that most gray
whale offspring (calves) are born in Mexican waters in and near the lagoons.
But more recent studies have revealed that a higher than expected number of
calves are actually born during the southern migration, as far north as
southern Oregon. Some mothers and calves have been spotted passing south
through the Channel Island sanctuary waters.
Gray whales begin leaving the lagoons for the
northward migration as early as mid-January; so the beginning of the
northbound migration overlaps slightly with the end of the southbound
migration near Baja California and Southern California in January and
February. The northward migration is shorter than the southward
migration, and it occurs in two distinct waves or 'pulses'. The earlier
pulse includes a larger cross section of the whale population. The later,
smaller pulse consists primarily of females and their calves.
The occasional observation of females and
calves or yearlings in the same kelp areas off the Channel Islands on
successive days has led to speculation that quiet kelp beds are of special importance to newborn and juvenile whales during spring.
Given that 60% of the kelp beds in the SCB
(the Southern California Bight--which extends
from Point Conception to Cabo Colnette, Baja California) are in CINMS waters,
some young whales might be expected to linger there. One reason the northbound
migration takes longer is probably due to whales stopping to feed on kelp,
which is more bountiful in the spring.
As with the fall/winter migration, during the
spring/summer migration some gray whales do not complete the migration to
subarctic or arctic waters, electing instead to spend summer and/or fall in
the waters of California, Washington, British Columbia, or Alaska. The number
of animals in these "summering" populations appears to be increasing, along
with the growth of the population at large (around 25,000 gray whales in the
North Pacific as of 1996).
