Here’s a video of a whole bunch of dolphins swimming along. They all routinely follow a trajectory that occasionally has them arc mostly - sometimes almost entirely - out of the water.
Do they do this because it’s a more efficient way to move than staying under the surface? For fun? To be able to see things on the surface? Some other reason?
So they can breathe.
You’re not the first to wonder! It’s obviously more than just breathing since they can hold their breaths for a long time.
But they wouldn’t need to get most of their bodies out of the water for that.
Obviously, as the second most intelligent species on the planet Earth
Just my WAG, but maybe it is a way to move more efficiently. Air has less resistance than water-- maybe jumping into the air gives them a micro-rest and allows them to move faster overall…kind of like being on a bike and coasting on the slight downhill parts.
If nobody’s there to film them, will they still do it? In other words, maybe they’re doing it in response to the boat/ship from which the video was filmed. As mammals, maybe it’s not unusual for them to check out the top sides of floating objects (not as unusual as it would be for a fish).
No cite, but my WAG is efficiency at high speed. The horizontal orientation of the cetacean tail makes it easier for them to propel themselves above the water vs. the vertical orientation of a fish’s tail. Humans doing the butterfly stroke use what is called a “dolphin kick” and (if they are doing it well) take a trajectory very much like the dolphins in the video.
Plus it’s probably a lot of fun trying to outrace a boat.
ETA: Found a cite: Au, D., Weihs, D. At high speeds dolphins save energy by leaping. Nature 284, 548–550 (1980). https://doi.org/10.1038/284548a0. Paywalled, but the abstract is free:
An observer may wonder whether a school of ‘running’ dolphins, consisting of numerous, wildly splashing individuals, is using the most efficient mode of locomotion, because splashing wastes energy. Dolphins exhibit at least three modes of swimming. In leisurely, unhurried motion, they break the surface briefly and gently, often showing little more than the blowhole. At a faster, ‘cruising’ speed, frequently at 3–3.5 ms−1 (6–7 knots), the animals are seen swimming primarily just beneath the surface, and there is still little splashing. (Behaviour and speeds of dolphin schools were observed from a helicopter and will be described elsewhere by D. A. and W. Ferryman.) Swimming speeds in this mode have been measured up to 4.6 ms−1 (9.3 knots). But in the fastest ‘running’ mode, the animals clear the water in sequential, parabolic leaps, accompanied by considerable splashing on exit and re-entry (Fig. 1). Leaps are interspersed with relatively brief, subsurface swimming. This swimming is common when dolphins are alarmed by vessels approaching within 500 m. We have examined dolphin swimming in terms of energy required per unit distance travelled and report here that beyond a certain ‘crossover’ speed, leaping must be more efficient than swimming.
The article does not seem to address the “it’s a lot of fun” argument.
It reminds me of the question, “Why do flying fish fly?” The agreed upon answer is to escape predators. They can move much faster out of the water. I once saw one go at least 150’ out of the water.
I’ve heard somewhere that dolphins get a bit of a boost when swimming near the bow of a ship. A google search turned up:
I’m not sure how well supported that is, but there seem to be plenty of sites repeating the same claim.
As for the video, it’s kind of hard to tell if that’s what’s happening. The camera is moving with the dolphins, so it must be on a vessel of some sort. But some of the dolphins are quite a distance away, so I don’t know how much of a boost they would get.
And the dolphins that breach the surface in the most spectacular fashion are the spinner dolphins (first short video I found on YouTube, there are hundreds):
\https://www.youtube.com/watch?v=IDpyBSb-aJQ
Why they do it? Nobody seems to know for sure.
My guess is that breaching helps when they want to be fast, though it takes more energy, like horses when they lift all four hooves from the ground when galopping. Penguins do something similar when they swim fast. But the spinning? Must be fun.
I have nothing factual to contribute but I could imagine that dolphin’s might need to spend some time oxygenating its blood, so an extended period of heavy, above water breathing could help with that.
Though again, I don’t know that that’s true. And I don’t know that this would be a better way of doing that, versus lazily taking some deep breaths while floating still.
Could it have something to do with the fact that they breathe air? Consider the fact that human competitive swimmers take a breath every three strokes or so, though they could undoubtedly swim an entire lap on one breath. Frequent breathing helps your endurance.
Moreover, dolphins like all cetaceans evolved from land mammals, and land mammals are generally built to move in a such a way that their spines flex and extend vertically and parallel to the direction of movement. (Think of how a cat bends and straightens its spine when it runs.) Similarly with dolphins when they swim, they’re already undulating their bodies in a vertical plane, unlike fish that swim by wiggling their bodies horizontally. (Fins normally don’t provide propulsion; they’re only there for stability.) When dolphins swim near the surface, it’s almost automatic that they’ll breach with every undulation.
Dolphins do swim like this when there are no boats around, I’ve been on land and seen them doing it.
Indeed, when Formula 1 cars started moving aerodynamically up and down last year they called it porpoising. Nice word, put translators in trouble.
Knowing dolphins, they probably get off on it.
Randy little buggers, swimming all up and down the Atlantic Ocean.
Seriously, I think one of the explanations is that dolphins do a lot of things simply because it’s fun for them. Complex minds require play. Young dolphins need play activities to learn hunting techniques. Dolphins just wanna have fun.
The bow wave riding could be energy saving, moving dolphins from where they are to where they want to go with maximum efficiency. Or again, it could just be a hoot.
To quote the Perfect Master Re: Pigeons and why they walk weird, “We do it because it feels good.”
TL;DR version of my earlier cite of a paper titled At high speeds dolphins save energy by leaping in the peer-reviewed journal Nature:
Minor hijack: At the Shedd Aquarium they have a large dolphin tank with a viewing area where you can watch the dolphins swim underwater. On one of my visits I noticed that some of the dolphins would roll over and swim upside down, sometimes for a fair distance. I can’t think of any reason they would do this, and there wasn’t an employee around who I could ask about it.
So, the same reason hydrofoil boats can go so fast on the same energy input: air drag versus water drag.