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Eastern Pacific Grey Whale Migration Facts

Location/Distance

  • The grey whales migrate between their summer feeding grounds in the Bering Sea and the winter breeding grounds in the lagoons of Baja, Mexico every year.
  • It is from 10,000 to 12,000 miles round-trip.

    

Mating

  • Females have a sexual cycle of two years. This includes the 12-month gestation period and 7-month nursing period.
  • Females typically produce one calf (baby) per sexual cycle once they have reached sexual maturity between ages 6 and 8.
  • Males will copulate with several females during each breeding season once they have reached sexual maturity at about 8 years old.
Eastern Pacific Grey Whale Map
Map shows the migration route of Eschrichtius Robustus (Grey Whales), ranging from Baja, Mexico to the Bering Sea. The map indicated the Chukchi Sea because some groups of the whales have been observed to go there.
  

Feeding

  • Gray whales are baleen cetaceans that bottom filter during their summer feeding period (4 months) in the Bering Sea. There are lots of zooplanktan, the main prey of the whales.
  • They feed on amphipods and other small invertebrates when available.
  • They eat, on average, 660 pounds of food per day, or 340,000 pounds per feeding season, so they can store enough energy to fuel their migration.

  

Migration Cues

  • While work is still being done in the gray whales' migration cues, it is known that the whales respond to the reducing amount of daylight hours in autumn as winter begins to approach. This cues the beginning of their southbound migration.
  • They also have an internal biological clock that tells the whales, via hormones, that it is time to migrate for breeding and calving.

  

Navigational Mechanisms

  • They rely primarily on the North American Pacific Coast to guide both their northbound and southbound migration. They stay within 1 to 6 km of the coastline.
  • Studies have also shown that the whales use a sun compass - they relate the position of the sun in the sky to the coastline and position themselves in the northbound or southbound direction.