Sea Lions May Be Rounding Up Anchovies for Humpback Whales, Then Taking the Strays

Humpback whales in California’s Monterey Bay catch their food faster when California sea lions are hunting the same anchovies, according to a study in Philosophical Transactions of the Royal Society B.¹ With sea lions around, the whales’ feeding rate was 23% higher, and they spent no detectable extra energy to get it.²

That matters because big predators sharing a crowded buffet usually means somebody loses out. Here, the evidence points the other way: the two species appear to make each other’s meals a little easier.

How the whales were measured

The researchers drew on a decade of tags attached to humpbacks. Of 56 tag deployments on whales hunting fish, 46 gave a clear enough picture of whether sea lions were present, for a total of 96 observation sessions.¹

Humpbacks feed by lunging: they surge into a school of fish with their mouths open and try to take in as many as possible in one gulp.² The team analyzed 1,808 of those lunges.

“Across 1,808 lunge-feeding events, whales foraging with sea lions exhibited a 23% higher feeding rate and a 16% shorter inter-lunge interval,” the authors wrote in the paper, as quoted by Discover Wildlife.²

In plain numbers, lunges rose from 17.0 to 20.9 per foraging hour. The wait between lunges dropped from 208.5 seconds to 175.7 seconds.¹

The whales did not have to work harder for it. Their speed, acceleration and maneuvering stayed the same, the energy cost per feeding attempt did not detectably rise, and the share of time they spent foraging didn’t change.¹² More food per hour for the same effort is the kind of deal most of us only get at a well-run potluck.

What the sea lions may be doing

The researchers suggest sea lions help herd anchovies into tighter, denser bait balls, so the whales can find and scoop them up faster.²³ The sea lions, in turn, appear to benefit from the whales’ leftovers.

“We observed sea lions foraging on individual, slow-moving anchovies separated from the school by humpback whale lunges,” the authors wrote, as quoted by Discover Wildlife.²

That benefit to the sea lions is based on observed behavior. The study did not measure how much more the sea lions catch.²

Part of why this works may be that the two predators order differently. A humpback wants the whole school in one mouthful; a sea lion goes after one fish at a time. The authors suggest that difference may limit competition, since the whales showed no rise in maneuvering effort when sea lions joined in.² That is an inference about cost, not a claim that the crowd never gets in each other’s way.

Partners, or just neighbors at the same table

It is tempting to call this teamwork, and Nautilus compares it to other cross-species hunting pairings such as dolphins and seabirds.³ The authors are more careful about what the whales are actually doing.

The question of “whether whales actively track sea lion activity or both predators simply converge on anchovy schools remains uncertain,” they wrote, as quoted by Discover Wildlife.²

Either way, the gatherings are not rare. Mixed groups of whales and sea lions are a common summer sight in Monterey Bay.⁵ One local whale-watching company, Sanctuary Cruises, logged 25 humpbacks feeding with about 60 sea lions on August 12, 2026, and 15 humpbacks with about 50 sea lions a week later.⁶⁵

For the anchovies, this is not good news. For anyone trying to understand how big predators share a busy ocean, the study offers a clearer picture of one arrangement that seems to work out for both sides.