Penguin Numbers Plummeting—Whales Partly to Blame ? « Sibylline's Blog

The second krill killer is actually a conservation success story—rebounding populations of whales.

“From what information is available, stocks of krill-eating whales are beginning to return, and their numbers are growing,” Trivelpiece said....

Nineteenth- and 20th-century whale hunts, which severely impacted populations of the giant marine mammals, appear to have ushered in a penguin heyday.

“We don’t have good data prior to the 1930s, but it appears that at least the 1930s to the 1970s were a real boom time for penguins, primarily because of the removal of competition in the form of whales.”

“Population data from that period is largely anecdotal and provided by the rough counts of British Antarctic workers. But even if you’re counting by the seat of your pants, the difference between 100,000 penguins in the 1930s and 500,000 or 600,000 in the 1970s is enormous.”
...
“Only in the last hundred years or so did krill come into their diet, when the whales were taken out of the system and there was a krill surplus,” Trivelpiece said.