Fifty years after they were hunted to near extinction, blue whales have returned to the sub-Antarctic island of South Georgia. Scientists at the British Antarctic Survey made the discovery while following up on a recent study which revealed that humpback whales are also returning to South Georgia.
The international research team analyzed 30 years worth of sightings, photographs, and underwater sound recordings to investigate how Antarctic blue whales are recovering after commercial whaling was banned in the 1960s.
Blue whales were once abundant off South Georgia before commercial whaling killed more than 42,000 individuals between 1904 and 1971. The giant fish vanished from this region, with only a single blue whale sighting between 1998 and 2018. By 2020, however, a survey in February recorded 58 blue whale sightings and numerous acoustic detections.
“The continued absence of blue whales at South Georgia has been seen as an iconic example of a population that was locally exploited beyond the point where it could recover,” said study lead author Susannah Calderan of the Scottish Association for Marine Science (SAMS).
“But over the past few years we’ve been working at South Georgia, we have become quite optimistic about the numbers of blue whales seen and heard around the island, which hadn’t been happening until very recently. This year was particularly exciting, with more blue whale sightings than we ever could have hoped for.”
The researchers used devices that can detect the loud, low frequency calls of whales over long distances. The team also collected records of whale sightings reported to the South Georgia Museum.
Overall, 41 individuals have been identified in photographs from South Georgia over the last ten years, yet none of these match the 517 whales in the current Antarctic blue whale photographic catalog.
“We don’t quite know why it has taken the blue whales so long to come back,” said Calderan. “It may be that so many of them were killed at South Georgia that there was a loss of cultural memory in the population that the area was a foraging ground, and that it is only now being rediscovered.”
The remote location, harsh weather, and lack of access to South Georgia greatly limit the opportunities for whale surveys, yet careful examination of the region is critical for future management.
“This is an exciting discovery and a really positive step forward for conservation of the Antarctic blue whale,” said study co-author Dr. Jennifer Jackson, who led the 2020 whale expedition.
“With South Georgia waters designated as a Marine Protected Area by the Government of South Georgia and the South Sandwich Islands, we hope that these increased numbers of blue whales are a sign of things to come and that our research can continue to contribute to effective management of the area.”
The study is published in the journal Endangered Species Research.
By Chrissy Sexton, Earth.com Staff Writer