A rare and surprising encounter with humpback whales delighted marine biologists, who were puzzled to spot them in a gathering of impressive size.
Research cruises in the southwestern region of South Africa stumbled across these magnificent creatures huddling in large groups of up to 200 to hunt and feed together.
The sightings occurred in the Benguela Upwelling System, a stream of oceanic currents that flow from St. Helena Bay all the way to Cape Point.
Equally remarkable was discovering their presence in these waters off-season. Several study expeditions reported chance meetings with humpback whales in October and November, when the creatures should have already started their migration to colder regions.
This time of the year typically finds the whales embarked on a journey to Antarctica, where they go to find food and spend the summer after giving birth and nursing their calves in warmer tropical waters.
The unusual behavior prompted an ample research into the feeding habits of humpback whales, which revealed a few unexpected facts about their nature and way of life. The findings were published in the journal PLOS One.
Humpback whales have been consistently described as solitary animals, which enjoy spending most of their days alone and seldom seek the company of others. Scientific literature reports rare exceptions of the animals gathering in arctic waters to feed in groups but of significantly smaller sizes.
In the past, researchers marveled at seeing the whales come together in congregations of no more than 15. Now, they are utterly bewildered to find them rounding up in "supergroups" of 20 to 200 animals.
According to study author Ken Findlay, from the Cape Peninsula University of Technology in South Africa, this type of whale social conduct is fairly unprecedented.
"No such dense feeding aggregations have been reported elsewhere in low or mid latitudes during Southern Hemisphere humpback whale migrations," Findlay explains.
Researchers have had the opportunity to observe this recent peculiar behavior on three separate occasions, during study trips along the Benguela Upwelling System in 2011, 2014, and 2015.
These sightings contradict what was previously known of these majestic creatures, suggesting they have a more gregarious nature than originally thought.
What Makes The Humpback Whales Assemble Here In Such Large Groups?
One theory is the abundance of prey makes the Benguela System particularly appealing. The study indicates a high prevalence of mantis shrimp in the area, which humpback whales have been found to favor.
Another possible cause for the whales amassing is the recent spike in their numbers, which could lead them to explore unfamiliar hunting territories to avoid exhausting their usual food supplies.
A third explanation could be the animals, whose populations have replenished over the past 20 years, are now reverting to an older hunting strategy. After a century of absence, the whales could be returning to their former feeding grounds due to the recent massive increase in their numbers.
"For the last few decades, suddenly they seem to have overcome some threshold and have begun to increase very fast," said Gísli Vikingsson, from the Marine and Freshwater Research Institute in Iceland.
Researchers are also considering the possibility that humpback whales have been habitually spending their summer in Benguela unbeknown to us. Findlay suggests this could have been happening all along in less frequented areas, where it would be difficult to observe.