The honest answer is: we don’t know. Not for certain.
I realize that’s not the tidy explanation you came here looking for. But it’s the truth, and I’d rather start with that than dress it up. Researchers have been working on this question for decades and the best they’ve managed is a list of plausible hypotheses. None of them fully explains the behavior. Several of them contradict each other.
What I can tell you, after five seasons watching humpbacks in Southeast Alaska, is what breaching looks like when it happens 200 yards off your bow. And a few patterns I’ve noticed that may or may not amount to anything.
What It Actually Looks Like
Most photos of breaching whales show a single frozen moment. The animal airborne, water streaming off its body. What the photos completely miss is the speed, the concussion of sound, and the sheer absurdity of the scale.
A humpback whale weighs roughly 40 tons. To breach, it has to accelerate vertically from depth fast enough to launch two-thirds or more of its body clear of the water. The splash when it comes back down can be heard half a mile away. The first time you see it happen for real, in person, your brain genuinely needs a second to catch up with your eyes. Something that large is not supposed to do that.
Some days on the water we don’t see a single breach. Other days they won’t stop. I watched 20 breaches in a single morning on our Hungry Whales Photo Tour last spring. One whale after another, sometimes the same whale multiple times, throwing itself out of the ocean and crashing back down. When they get going like that, it feels purposeful. Deliberate. But whether it actually is, that’s where the science gets murky.
What the Researchers Think
There are several hypotheses. The main ones, briefly:
Communication. A 40-ton animal hitting the water makes a percussive boom that travels a long way underwater. Some researchers think breaching functions as a long-range signal, particularly in rough conditions when vocal communication might get drowned out. A 2017 study found that surface-active behaviors like breaching increased when groups of humpbacks were spread farther apart, which supports this idea.
Parasite removal. Humpbacks carry barnacles and whale lice. The impact force of a breach could knock some of those off. It’s intuitive and it’s been in the literature for years, but nobody has actually measured barnacle loss before and after a breach in any rigorous way. So it remains a reasonable guess.
Play. Calves breach constantly. Way more than adults. If play serves a developmental function in whales the way it does in other intelligent mammals, then breaching in young animals could be practice. Strength and coordination building. This makes sense to me, though I’m not a marine biologist and my opinion isn’t worth much here.
Display and competition. On breeding grounds, males use breaching as part of competitive behavior. It might signal fitness or dominance. But whales also breach on the feeding grounds, thousands of miles from any breeding activity, which makes this explanation incomplete at best.
Respiratory clearing. A hard re-entry could help clear the airways. This one shows up in the literature but doesn’t get cited as often. It’s hard to test and harder to build a compelling case around.
Pectoral Slapping
Pectoral fin slapping is probably the strongest evidence for the parasite theory, even if nobody’s proven it conclusively. A whale rolls onto its side and hammers the water surface with one pectoral fin, over and over. Sometimes for minutes at a stretch.
Those fins are 15 feet long on an adult humpback and they accumulate serious barnacle loads along the leading edge. The slapping generates enough force that you can hear it from a surprising distance on a calm day. Whether it’s actually knocking parasites loose or serving some completely different purpose, the whales seem committed to it.
I’ve watched them do it long enough that you start to wonder if they’re going to get tired. They don’t seem to.
What I’ve Noticed (For What It’s Worth)
These are observations from the water. Not conclusions. I want to be clear about that.
Breaching clusters. When one whale breaches, others nearby tend to follow. I don’t know if the first breach triggers the rest or if all the whales are responding to the same thing I can’t detect. But the pattern is consistent enough that when we see one breach, I start watching the surrounding water because more are usually coming.
Weather seems to matter. More surface activity on days with some chop or wind. That could support the communication theory, if the whales switch to louder physical signals when the water is noisy. Or it could be coincidence. I don’t have data, just a feel for it after a few hundred days on the water.
Breaching doesn’t seem to track feeding. We’ve seen whales breach during active bubble-net feeding and on days when nobody seems to be feeding at all. If it were purely functional, you’d expect a tighter correlation with something. I don’t see one.
My best guess, and it really is just a guess, is that breaching serves multiple purposes in different contexts and that humpback whales sometimes do it for reasons we haven’t figured out yet. Maybe reasons they haven’t figured out either. That’s fine. Not everything needs a clean answer.
Photographing a Breach
This is the single hardest thing to photograph from a boat.
The window from first appearance to splash is about two seconds. If you’re already looking through the viewfinder, you’re zoomed in too tight to find it. If your camera is in your lap, you’re too slow. The approach that actually works: keep the camera up, zoomed wider than your instinct tells you, and react.
Here’s the thing though. When a whale starts breaching, it often does it again. And again. Miss the first one, be ready for the second. That repeat behavior is your friend. On a day when they’re at it, you’ll get your chances if you’re patient and you keep your gear ready.
Over five days on our Humpback Whales Photo Tour, the probability of seeing breaches is solidly in your favor. I won’t promise it, because that’s not how this works with wild animals. But on the mornings when they decide to put on a show, 20 breaches before lunch, you’ll remember it whether or not science ever agrees on why they do it.
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