John Calambokidis is a senior research biologist who has studied marine mammals for more than 30 years. He has served as the principal investigator on more than 40 studies and co-authored more than 50 scientific papers and three books on marine animals. His recent work has focused on the impact of human activities on the status, movements and underwater behavior of blue, humpback and gray whales. His work has taken him across the North Pacific from Central America to the coast of Alaska. Over the last 20 years, he has created a unique photographic database of more than 2,000 individual blue and humpback whales from the U.S. West Coast. In 1999, he began working with National Geographic using a suction-cup-attached Crittercam to learn more about the underwater behavior of blue whales. Calambokidis is also a co-founder of Cascadia Research, a charter member of the Society for Marine Mammalogy and an adjunct faculty member at Evergreen State College in Olympia, Washington.

Nat Geo: When did you know you wanted to study whales?

John Calambokidis:I began by studying seals when I was in college and initially focused exclusively on them. But then I quickly became interested in whales since I was encountering them in my work with seals, and even less was known about them.

Nat Geo: What was the most challenging aspect of the expedition?

John Calambokidis: The long period at sea, and traveling to such a remote location was hard on us. The research boat we used was small, and we faced inclement weather. And working so close to such large animals is always challenging.

Nat Geo: Was there any part of your voyage that was dangerous, where you put your life at risk to conduct your research?

John Calambokidis: Most of my work is conducted from small boats often far offshore, and working close to whales can lead to some unpredictable encounters. A blue whale is much bigger than the boat itself.

Nat Geo:What was the most memorable day of the expedition?

John Calambokidis: One day we were able to not only deploy several of our suction cup tags and gather the first data conclusively showing feeding, we were also able to see something very unique. We came across some larger groups of blue whales engaging in courtship behavior -- that was different from anything I had seen before.

Nat Geo: Why is the study of blue whales important? What role do they play in the ecology of the ocean?

John Calambokidis: As the largest animal that had ever lived, blue whales were being hunted to the brink of extinction, and many scientists were not sure they could ever recover. To think we drove earth's largest animal to extinction and none of our children would ever get to see such an animal would be terrible. We still do not fully understand the way blue whales interact and affect the ecosystem as a whole, so we really don't know how their disappearance would alter things.

Nat Geo: What measures are currently being taken to protect the blue whales?

John Calambokidis: There is a moratorium on commercial whaling, but several nations exploit loopholes to get around this. Fortunately, none have resumed hunting the blue whale species. They are protected from intentional or negligent harm under the Marine Mammal Protection Act. Their "endangered" status means that U.S. agencies have to consider the impact of any actions that might hurt them.

Nat Geo: What advocacy groups do you work with to help protect the whales?

John Calambokidis: The Natural Resources Defense Council is the primary conservation group we work with.

Nat Geo: Is there legislation you think we need to pass to allow for greater protection of the whales?

John Calambokidis:Current threats to blue whales include underwater noise, climate change and ship strikes. Five blues were killed by ship strikes off the Southern California coast last year alone. Legislation dealing with any of these threats would be helpful.