I had a conversation tonight about the Flipper story already discussed in this SD thread.
The emotional impact of the story relies on the assertion that dolphins not only can stop themselves from breathing, but that they consciously direct each and every breath. The version my conversational partner related was even more explicit that dolphins think about each and every breath during their lives.
I’m having some trouble believing that prerequisite of the story – not dolphin suicide, but that dolphins breathe consciously and have to think about every breath they take, and that that is fundamentally different from the way we humans breathe. After all, I can hold my breath underwater too, and wait until I surface to breathe. But more to the point, wouldn’t it be a gigantic drain on the attention span and brain resources of a dolphin to spend its whole life planning each breath?
Given that dolphins are mammals, it seems to be characteristic that mammalian brains have developed in layers, and that the more intelligent species have more elaborate development of the outer layer.
The layers are:[ul]
[li]the brain stem (medulla and cerebellum)[/li][li]the midbrain (thalamus and the hypothalamus)[/li][li]the forebrain (containing the cerebrum and the cortex)[/ul] [/li]
In mammals (and even in lower species from reptiles on up) the medulla of the brain stem controls automatic processes like breathing, heartbeat, and digestion). Thus even people with sever injury to the outer layers of the brain and in a coma still have the brain stem working to ensure that they breath and their heart beats.
So since dolphin brains follow this same pattern, the medulla of their brain stem would control breathing automatically, so they should not have to ‘think about each breath’. Living in the sea, they would be able to override this automatic breathing so they could hold their breath while underwater. But that doesn’t seem like the same thing as having to think about each breath.
I agree - if for no other reason than that such arrangement that would be be quite likely to result in the dolphin drowning if it became distracted by prey/predator/sex/shiny thing while underwater and stayed down too long or took a breath at the wrong time. It seems likely evolution would deprecate such an arrangement in favour of a more autonomic approach.
Besides which, how would anyone know whether dolphins make a ‘conscious’ effort to breathe? Are there any dolphin mind readers about, or dolphin autobiographies with chapters titled e.g. ‘Breathing, why I do it, and how’?
I saw this thread earlier but didn’t get a chance to reply - sorry about bringing it back from the dead…
We do know for sure that cetacean (and pinniped, for that matter, but since they’re not closely related it’s not relevant to the OP) breathing works differently from other mammals.
We know this because when you anesthetise them, they stop breathing and die.
It could be that dolphins are in conscious control of their breathing as Kevin Walsh asserts here:
In which case the real barrier is not the brainstem’s automatic response that t-bonham@scc.net - it’s voluntary control of the muscles that allow the lungs access to the air. It becomes completely irrelevant that the diaphragm and lungs are under involuntary control because the blowhole is not open without voluntary control.
In addition, there seems to be a depressed response to CO[sub]2[/sub] to trigger the automatic response in the first place.
I should also mention that there are some who are skeptical of this view.
From here.
So it is likely more complicated than simply that marine mammals are conscious breathers. But current practice with marine mammals under anesthesia does demand use of artificial ventilation to keep the animal alive - unfortunately, Walsh’s presentation (no journal article of that name shows up in a search) doesn’t seem to be available online.
Without being able to read it, I fall on the side of the other Walsh (Kevin) I quoted above.
Perhaps anesthesia works differently in marine mammals than other mammals? Possibly - that could explain both results. That brings us back to slaphead’s comment:
That’s the problem - we don’t really know easily. Some MRI or PET scans are in order, but I haven’t seen that work done anywhere.
Walking and running are completely voluntary. Once hardly thinks about every step or every variation when climbing, turning or even just going in a straight line.
I can’t contribute anything of use to this thread, I’m just popping in to mention something which I’ve found strange since my childhood: Once you start thinking about breathing consciously, you actually have to think about every breath. You can’t return to subconscious breathing until your mind is distracted and your attention directed at another matter.
I don’t think that’s accurate. Drowning victims are commonly found with water in their lungs from having tried to breathe underwater.
People can consciously hold their breath while underwater, but only for a short time – after that the automatic brain response takes over, and the body starts trying to breathe, even if underwater.
Exactly. Just saying that dolphin breathing is done via voluntary muscles doesn’t mean they have to concentrate to breath. It also doesnt mean that getting “distracted” would make them forget to breath.
Geez, how often have you been driving and been completely distracted or mentally preoccupied with something else? Not difficult. Let alone simple things like walking.
It’s not very difficult to accept that dolphin respiration can be maintained solely with voluntary muscles.
That’s a really good point. Voluntary muscle does not mean all awareness is focused on making it work, and conscious breathing versus unconscious asphyxiation does not mean conscious effort vs. unconscious asphyxiation.
This doesn’t make sense to me. If a dolphin’s breathing were automatic, wouldn’t they breath in and draw in water some random point in swimming? Dolphins only need to breathe once every few minutes. They wouldn’t forget they need to breathe anymore than if you were under water for a minute and your brain was screaming “too much CO2! surface!”.
How would automatic dolphin breathing even work? They need to come to the surface to breathe. If they automatically took in breath at regular intervals, how would they dive?
I was listening to a BBC radio show a while ago about how this ties into the aquatic ape theory of human evolution - land mammals are strictly voluntarily breathers generally. Humans are unique in even having the ability to hold their breathe voluntarily. Which is cited as part of the evidence of a semi-aquatic history for our species.
It seems impossible for it to be involuntary. It seems logical to say their “default mode” is to hold their breath, and they have to take a series of actions for every breath they take in their life. That doesn’t mean they have to concentrate on it. It is probably the most natural thing in the world for them. When they have the need, they instinctively grab a breath, like I would scratch an itch when I feel it.
Here’s a question. Can a dolphin surface without taking a breath?
Absolutely. They can hang out with their head above the water for long periods of time. I’ve even seen them sleep (yes, with one eye open) with their body floating at a depth which allowed the blow hole to stay above the surface for the entire time. So when they took a breath, they just breathed and didn’t need to move.
Try counting the number of times you breathe per minute. Once you start thinking about it, it’s difficult to do this without controlling your breath thus altering the count
Apropos of nothing, but I was watching some bottlenose dolphins off the coast of Santa Cruz this Saturday. The water was flat and the dolphins were <100 meters away - even with great viewing conditions, we couldn’t see the blows off the dolphins’ breathing. We also could only see them when they were at the surface, about 3 minutes out of the 20 minutes total we spent watching the dolphins.
If it weren’t for watching dolphins in captivity (and the ones that approach boats closely,) we would know considerably less than we do about dolphins and other cetaceans. With the rare ones, like beaked whales, they’re still very much a mystery, and some species are only known from specimens that have washed ashore.
