Scientists know much about the magnificent humpback whale, from its long migration routes to its haunting songs. Far less, however, is known about its history. Just how many of these behemoths used to glide through our oceans? Though conservationists estimate that commercial whaling reduced populations by 90 percent, they have never been able to accurately assess pre-whaling numbers.

A new study co-authored by WCS hones in on the answer. Using hundreds of genetic samples from whales across the Atlantic and Southern Hemisphere, researchers estimate that more than 100,000 humpbacks thrived in North American waters before commercial whaling became widespread. This figure is two to three times higher than the amount calculated using old whale records, and four to five times greater than current populations.

You might be asking yourself: why does historical data matter?

The question becomes increasingly important as some members of the International Whaling Commission call for the level of international protection for humpbacks to be dropped based on their remarkable comeback over the past several decades. Today, the North Atlantic harbors more than 17,000 of these mammals. But now that the genetic studies prove their historical population size was much larger than previously assumed, conservationists say the threshold of recovery should be revised, too.

“Our current challenge is to explain the remaining discrepancy between the historical catch data and the population estimate generated by genetic analyses,” said Dr. Howard Rosenbaum, study co-author and Director of WCS’s Ocean Giants Program. “The gap highlights the need for continued evaluations of whale populations, and presents new information informing the debate and challenges associated with recovery goals.”

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