Humpback whales in the southern hemisphere have been exhibiting odd behavior over the past few years: typically a solitary species that only temporarily gathers in pods of up to a dozen individuals, groups of up to 200 whales have been gathering in spots off of the west coast of South Africa. In addition to this oddity, these whales typically aren’t found that far north in the summer, preferring feeding grounds closer to Antarctica.

Researchers are at a loss when it comes to explaining this new behavior, although one idea suggests that this is actually a normal activity, interrupted when the humpback’s numbers dropped due to over-hunting in previous centuries.

Researchers observing the whales have found that the groups are indeed feeding, due to observed “repetitive and consecutive diving behaviors… and the pungent, ‘fishy’ smell of whale blows,” according to a paper published in PLOSone. Humpbacks have been known to gather in smaller groups to herd schools of fish for hunting purposes, meaning this might be a reason for the meet-up.