Most humpback whales have made a comeback. In 2016, after decades of counting, NOAA Fisheries decided that 9 of 14 humpback populations had recovered enough to come off the US endangered species list. For most of the twentieth century, humpbacks were hunted toward oblivion. Now, by the numbers, most of them are back.
Most, but not all.
One group sat out the comeback entirely, and it happens to be the strangest humpbacks on the planet: a few dozen whales in the Arabian Sea that have been cut off from every other humpback for tens of thousands of years and, unlike their relatives, never migrate anywhere.
We are not marine biologists or conservation scientists. What follows is our reading of the published research, and the findings here describe patterns across whole populations, not guarantees about any single animal or a settled last word on a young field of study.
How most humpbacks climbed back
The recovery rests on two decisions. The United States listed all humpbacks as endangered in 1970. And the International Whaling Commission banned commercial whaling in the mid-1980s, a move NOAA Fisheries credits with turning the population trend around. Take away the harpoons, and a slow-breeding animal can, over enough decades, rebuild.
The scale is easy to underestimate. There are now roughly 100,000 humpbacks worldwide. Robert Pitman, a marine ecologist at NOAA, was blunt about taking most of them off the endangered list. “The data behind the humpback delisting is solid,” he said. NOAA split the species into fourteen separate populations. Four stayed endangered, one was downgraded to threatened. The comeback was real, but uneven.
The whales that stayed put
Every humpback anyone had studied did roughly the same thing: feed in cold polar waters, travel thousands of kilometers to warm tropical waters to breed, then head back. The longest recorded humpback migration runs more than 9,000 kilometers. It’s one of the defining facts about the species.
The Arabian Sea whales don’t do it. They stay put all year, feeding and breeding in the same waters, mostly off the coast of Oman. A recent satellite-tagging study confirmed the year-round presence of this population in a small area. As that study notes, this is the only humpback population known to skip the long seasonal migration. They are not a separate species, just the only humpbacks anywhere that never make the great commute.
Why they stay is still an open question. Tim Collins, a co-author on the genetic work, put the appeal of the puzzle plainly: “The epic seasonal migrations of humpbacks elsewhere are well known, so this small, non-migratory population presents a wonderful and intriguing enigma.”
Why isolation is the whole problem
The odd behavior turns out to sit on top of something deeper. A genetic study published in PLOS ONE in 2014 compared DNA from the Arabian Sea whales with populations in the Southern Hemisphere and North Pacific. It found the Arabian Sea group had been cut off from all the others for an estimated 70,000 years. Howard Rosenbaum, the study’s senior author, called them the most distinct population of humpback whales the study had found.
That distinctiveness is fascinating, and for conservation, a problem. When a population is sealed off like this, no whales wander in from elsewhere to refresh the gene pool or add to the numbers. Every other recovering humpback population is, in effect, part of a larger connected system. These whales have no such backup. On the best current estimate there are around 82 of them, fewer than a hundred in all. What’s there is all there is.
Same species, harder waters
They also live in a difficult neighborhood. The Arabian Sea carries some of the world’s busiest shipping traffic, and the two biggest threats to whales that stay in one place are getting tangled in fishing gear and being hit by ships. The scale of accidental catch in the wider region is hard to picture: one analysis estimated as many as 4.1 million small whales and dolphins died in Indian Ocean tuna gillnet fisheries between 1950 and 2018. For the humpbacks specifically, the same source reports that 30 to 40 percent of whales photographed off Oman carry scars from being tangled in gear.
There is history here too. Illegal Soviet whaling killed at least 242 of these humpbacks off Oman, Pakistan and India in the 1960s. For a population this size, that was a wound it has never had the numbers to heal. A whale that could migrate might move away from the worst of the danger. These whales can’t. Their range is small, fixed, and overlaps almost exactly with the industry around them.
Endangered, and possibly worse
Officially, the Arabian Sea humpback is listed as Endangered on the IUCN Red List. The authors of the 2014 genetic study argued the label undersells the risk, and recommended moving it up to Critically Endangered.
Rosenbaum did not soften his view. He called them “the world’s most isolated population of this species and definitely the most endangered.” That is one team’s reading of one body of evidence, but the gap between the official status and the researchers’ recommendation captures the whole tension around these whales.
We’d resist filing this away as a small, doomed group of animals. What makes the Arabian Sea whales matter is exactly what makes them fragile. They are a living record of a line that broke away from every other humpback around the time modern humans were leaving Africa, and they built the humpback way of life without the migration that supposedly defines it. Whether they can hold on in a warming, busier ocean is a hope, not a forecast.
The global figure, nine of fourteen populations back from the brink, is genuinely good news. It is also an average, and averages smooth over the places the success story never reached. A few dozen of the most distinctive whales alive, in waters that keep getting busier, still waiting on a rescue the headline numbers already assume has happened.