I don’t get how something so big just eats grass like a cow. If we eat vegetables all day we won’t get fat or super big so how are they able to do it? I feel like eating grass all day is not very filling.
In: Biology
They eat an absolute massive amount of plants. A large cow eats 60 pounds of hay (dried grasses) per day, and much more fresh grass (because they eat more water weight). A man who is 1/10th the cows size would get about 4 days worth of calories from an proportional amount (6 lbs) of dried foods like (fruit or meat).
In addition to the other answers, there’s the bigger ecological one. EVERY animal just eats grass and plants. Herbivores eat it directly, carnivores eat it after it’s been processed through herbivores. But turning grass into flesh is pretty inefficient – even with modern agriculture it takes about 10 calories of grain to make one calorie of meat.
So carnivores are at a calorie disadvantage, so to speak, which is why they have much smaller populations and often smaller bodies as well.
You have cause and effect the wrong way round.
Grass and leaves are not very nutritious. It can therefore be effective to have a large and complex digestive system to extract calories from them. This necessitates a large animal.
Also an animal which eats grass has few excess calories, which means it cannot spend its life running. Being large is an effective defence mechanism for a slow moving animal.
Which leads to the question, how do sheep exist?
They have very efficient digestive systems that have specialized to extract energy from plant material. The tradeoff is that they need to eat a lot of plants to meet their energy needs, which means they spend a lot of their lives eating. They have the advantage of ready access to food for which they have to do very little work.
Carnivores are the opposite extreme. They don’t have to eat as frequently, but they have to expend a lot of energy in order to hunt, kill, and consume their prey.
Omnivores like us can reap the benefits of both. We can obtain most, but not all, of our essential nutrients from a plant-based diet and we can consume animal meat/fat in order to obtain energy and protein for our metabolism, as well as obtain the critical nutrients that we can’t get from plants.
Okay so basically herbivores eat plants which are the first on the food chain. As the food transfers down the chain, the energy received per step is reduced by a factor of x.
If you are really 5 then imagine this. Plants have 100 hp. A rabbit eats the plants and uses 90 hp for itself and leaves behind in its body 10. A lion eating the rabbit only receives the 10 as compared to the 100 received by the rabbit.
Also plants are made up of cellulose. Herbivores have digestive systems specifically designed for breaking down cellulose whereas humans have a more generalised system and do not digest cellulose. Hence veggies are also called roughage as the help fill the stomach but don’t actually give you enough energy.
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