When I take my dog for a walk it seems to me that the going is easier for him, what with four legs, than for me.
So that the effort required for me to walk 5 miles might be equivalent of the dog walking say 15.
Say in calories used over the distance and taking into account body weight.
Has anyone ever worked out a “man equivalent” of the effort other animals use to move.
So that say, athlete running a mile, is the same as a racehorse running what, 5 miles? And a racing pigeon flying 20? A salmon swimming 100?
I guess that perhaps apart from valuable race horses no one has ever bothered to measure or work out the “effort” other animals take to move.
I don’t think it is as ‘simple’ as you might suppose.
Mammals have different types of muscles. Offhand I know there are ‘fast twitch’ and ‘slow twitch’ muscles each with their own purpose. Different animals have these in varying degrees.
Take a cat versus a dog for instance. IIRC the cat has much more of the ‘fast twitch’ variety of muscle. As a result they are capable of astounding bursts of speed and amazing jumps…far exceeding what any dog can do. For this ability however they pay for it in endurance. Cats cannot do long distance running where a dog would easily surpass the cat. Watch big cats in Africa chase their pray. It is all about time for both predator and prey. The cat can maybe chase its dinner for a minute at top speed. The Impala or Zebra can run at top speed for much longer. If it can evade the predator cat for a minute or so the cat will give up (it has to…its body simply can’t manage more). If I recall rightly a Cheetah expends so much energy in a chase that it has something like three chases in it before it ‘looses’ the calorie expenditure bill. That is, on its fourth chase it will have expended more energy that it will get back from that one meal of, say, an Impala. In short it won’t survive long if it isn’t successful more frequently than most animals.
Then add in other things such as skeletal structure. Some animals are geared for jumping (cats have an effective lever setup in their hind legs that improves jumping ability but again sacrifices running ability). Leg length, suppleness of body (a cat can bend its body sufficiently to put its hind legs almost to its head when running and use its entire back to uncoil for speed…dogs and horses can’t to that extent), length of body, metabolic rates, lung and heart capacity and so on all interact to get to the bottom line of efficiency.
In the end it all depends on what the animal is built for which relates to its survival strategy. Everything is a tradeoff…excel in one area and you give something up somewhere else. Interestingly is a basic comparison between mammals and reptiles. Mammals can regulate their own body temperature allowing for a much greater variety of habitats and tolerance to their environment. Why do reptiles succeed so well? Because their cold blooded nature requires FAR less food to operate than warm-blooded animals do. IIRC loosely something like 12:1 (e.g. for every pound a cold-blooded animal consumes a warm-blooded animal would require 12 pounds everything else being equal). Some snakes need only eat once or twice a year!
This might not answer all of your questions, but the study of avian anatomy does illustrate that birds have evolved some very efficient lungs (among other things) to account for the massive amounts of energy and oxygen used during flight.
Unlike our lung (which are like a bellows or a balloon that fills with air going one way and empties with air flowing another) the avian lung allows for a constant one-way stream of oxygenated blood to be passing through the lungs at all times. There are even hollow areas in the bones of the avian skeleton which can provide air/oxygen for the blood stream even if a bird’s airway is obstructed.
The link has a lot more info about the circulatory system and other adaptations. So I think the general idea is: Yes, birds use massive amounts of energy and oxygen, pound for pound, when you compare them to humans (even our top atheletes). However, natural selection has provided them with a highly adapted anatomy that allows them to operate at that level quite successfully.
On a related note, Cecil explains another adaptation that birds have undergone that involves myoglobin concentrations in their muscle tissue.
Myoglobin is used for oxygen transport, so you can imagine how it would be advantageous for a bird to have lots of it in their muscle tissue. Chickens are flightless and as such they have “lost” the high myoglobin concentrations in their breast meat. Turkeys as well. If you’ve ever eaten duck, you’ll notice that the breast meat is dark, full of myoglobin, because they use it in flight.
Whales also have high concentrations of myglobin, which allows them to dive deep for extended periods of time.
"I guess that perhaps apart from valuable race horses no one has ever bothered to measure or work out the “effort” other animals take to move.
Or have they?"
Ah, you need to watch more Discovery chanel.
Kangaroos get a “spring like” effect in their legs while jumping, some fast moving fish (eg, tuna) use turbulance effects to move more quickly thru water. And let’s not forget the lovely vulture, which doesn’t use much effort at all to fly (glide).
Humans, by the way, are pretty efficient. Turns out upright walking is a good way to cover long distances. Most people would probably think humans were one of the least efficient locomotors out there.
Generally, O[sub]2[/sub] consumption is used to determine the energy costs of locomotion. For running, in most mammals, the energy progression is linear, based on speed - that is, you run faster, you use more energy (and consume more oxygen). Not too surprising. Dogs tend to do better than smaller animals like squirrels or mice when it comes to the energy expenditure of running; again, this should not be too surprising, since dogs possess many cursorial adaptations (i.e., adaptations which make them better runners), while mice and squirrels don’t. Also, larger animals tend to use less oxygen at a given speed than smaller ones.
For the same body mass, swimming appears to be the most energy efficient mode of locomotion, followed by flying, then by running. Of course, there is a very small overlap in body sizes for making such a comparison, since most flight-capable birds tend to be very light (typically ~1 kg or less). Note also that this assumes animals adapted to such modes of locomotion. A swimming duck (which is primarily adapted for flight, with secondary adaptations for swimming), for example, is less efficient than a swimming fish (a swimming duck rates about the same as a running mammal of comparable size). A swimming human is even worse.
Flight is the most efficient in terms of energy spent per distance travelled. For long distances, this usually includes a mix of soaring and flapping flight (with flapping requiring more energy than soaring). In terms of absolute cost per speed, flight tends to be less efficient than running, but much higher speeds are attainable. A graph of energy consumption vs. speed for flight is not linear, as it is for running. The graph tends to be “U”-shaped, resulting in a speed wherein the energy cost is minimized (though still fairly high).