A key population of humpback whales is in recovery after it was pushed close to extinction by centuries of exploitation, according to a new study.
Western South Atlantic humpbacks were reduced to a few hundred in the 1950s, after once totaling a number of 27,000.
But efforts to preserve the animal have been rewarded, with numbers now estimated to stand at 25,000 and 93% of their pre-exploitation levels, a study published by the Royal Society reveals.
One of the study’s authors, Dr Alex Zerbini, said it demonstrated the successful impact of “conservation efforts.”
“If you manage animal populations properly, animals can thrive, as shown here,” he told CNN.
The wider humpback whale species was devastated by whaling between the late 1700s and the mid-1900s – with estimates that 300,000 of the animals were killed.
The International Whaling Commission (IWC), the global body overseeing the conservation of whales, recognizes seven types of humpbacks in the Southern Hemisphere.
Zerbini, a senior research biologist on marine mammals for 25 years, distinguished between two key periods in whaling. He defined them as “pre-modern” and “modern.”
“Pre-modern” whaling was more rudimentary in nature, with hunters jumping in boats and chasing after whales with handheld harpoons. Whaling practices from the late 1800s and early 1900s involved more advanced practices including steam-powered vessels and the use of explosive harpoons.
And when it comes to whaling, humpbacks are pretty vulnerable. The fact that they are slow-moving and tend to enjoy coastal waters makes them a prime target.
They are also desirable to hunters because of their high amount of body fat, Zerbini said.
The western South Atlantic humpbacks on which the study focuses migrate towards summer feeding grounds in the South Atlantic.
They spend 4-5 months of the year breeding in warm waters and more tropical conditions and then move south to feed and devour krill for 2-3 months of the year.
The whales feast near the South Georgia and South Sandwich Islands in late spring and remain there until the autumn.
However, it is exactly this migration which has brought them in direct contact with whalers over the years – crippling the population and impeding the animals’ ability to thrive.
Whalers would set up stations in South Georgia and slaughter the whales in large numbers. Nearly 25,000 whales were caught over approximately 12 years in the early 1900s, according to the study.
It was only during the 1960s that scientists began to realize that the animals were declining on an unsustainable level. By that time they were on the edge of extinction.
The IWC moved in to ensure greater protection for the animals, allowing them to recover and replenish in number.
This study, which used a combination of observation and scientific modeling, was done because previous studies on South Atlantic humpback whales “weren’t correct anymore,” according to Zerbini.
Zerbini says the study is distinct from past research because it allows for a “correction factor.” It takes into account whales who were “struck and lost” – essentially whales that were killed or died but not caught. Previous studies have a degree of inaccuracy because they don’t account for this.
The study also looks at how the revival of South Atlantic humpbacks may affect the wider ecosystem. The whales are increasingly searching for more krill, so they are competing with species of penguin and seals around the island of South Georgia. It says more data is needed to understand this impact.
Zerbini said the findings showed it was possible to bring severely depleted populations back from the brink.
“This is good news. Despite all the killing that has happened, conservation efforts can have a positive impact and if you protect animals, this shows numbers can grow.”