Giant orcas (killer whales) are going missing along the California coast. Wild Chronicles sets out to find the culprit before it's too late.

  1. There are two populations of orcas in Canada's Pacific Northwest, permanent residents and "transients," or migratory animals who are just passing through. What is the difference in diet between the two populations?

    • Answer

      Permanent residents mostly eat fish, while transients prey on marine mammals such as seals.

  2. Why doesn't Nancy, the biologist, recognize the pod of orcas in Monterey Bay?

    • Answer

      The whales are not the regular transient pod that Nancy expects. The new pod is a group of permanent residents from Canada.

  3. What behaviors distinguish the permanent resident pod from the transient pod?

    • Answer

      The permanent residents are generally much more social, and display behaviors such as breaching and spyhopping.

  4. How does Nancy evaluate the health of the orcas? What does she find?

    • Answer

      Nancy tests samples of the orcas' blubber, taken with a dart gun. These blubber samples showed very high levels of PCBs, a toxic substance.

      Marine biologists think the toxic PCBs may be contributing to the shrinking population of orcas along the West Coast—that PCBs may be the real "secret killer."

breach
Verb

behavior exhibited by whales, when they jump above the surface of the water.

Noun

edge of land along the sea or other large body of water.

culprit
Noun

person responsible for an offense or fault.

killer whale
Noun

carnivorous whale, actually the world's largest species of dolphin. Also called an orca.

PCB
Noun

(polychlorinated biphenal) chemical substance that can occur naturally or be manufactured that may cause cancer.

pod
Noun

group of whales or dolphins.

spyhopping
Noun

behavior where an aquatic animal pokes its head vertically out of the water.