"It's a perfect opportunity for the calf to gain the experience it needs to learn how to hunt a gray whale and then feed on it later on," Black said. Killing a large whale is too dangerous for the calf, but as a spectator, it picks up lethal techniques like ramming, drowning, and biting the prey.
But even skilled teamwork may not ensure a calf's survival. In recent years, scientists revealed that resident killer whales were heavily contaminated with deadly toxic chemicals.
"Residents are showing up with immuno-deficiency problems, reproductive incompetence, and some adolescent males are dying off," said Ken Balcomb, a marine biologist for the Center for Whale Research in Friday Harbor, Washington, who has studied killer whales since 1976.
"The average life expectancy for a male resident is 29 years, but lately adolescent males are dying from age five to late teens," Balcomb said.
To learn more about the toxin levels and determine the general health of this species, Black is taking blubber samples of the transients as they feed on the gray whale carcass.
Black uses a four-foot-long (1.2-meter-long) dart gun to get her sample. She is one of a select group of scientists permitted to take blubber samples from killer whales.
Black sends the samples to the Northwest Fisheries Science Center in Seattle, where technicians analyze blubber for organochlorines (OCs) which are toxins like PCBs and DDT.
New results from Gina Ylitalo, research chemist at NWFSC, reveal disturbing news. "California animals contain the highest levels [of Ocs]. OC concentrations in transient killer whales were much higher than those found in residents oroffshore whales," Ylitalo said.
Life at the top of the food chain has its liabilities.
"The fish in the oceans transfer those chemicals over here and (since) killer whales are the top predator and they're eating seals, sea lions, dolphins and whales, they're bio-accumulating those chemicals," Black said. "They end up with the highest levels of all."
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