system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some animals (like spiders or lizards) spend so much time just doing nothing? What is happening and why?
gpt
Most organisms are in a constant struggle for energy. Obtaining energy is dangerous, you have to leave your save burrow or go risk injury in a hunt.

That's why many organisms develop strategies for minimising the risks they need to take. And one of the most popular strategies is simply having simple, low demand physiologies, slow metabolisms and generally low energy needs.

Warm blooded animals are fairly unique. We're like a car with the engine constantly running. That means we're ready to go from zero to a 100 right away but we're also guzzling gas constantly, even if we're standing still. That's why warm blooded animals need toc constantly eat. Some of the smaller more high energy creatures like humming birds can starve to death in a matter of hours.

By comparison, cold blooded animals waste zero energy on body heat. The downside is that they need to warm their bodies up with external heat like sunlight in order to get their digestive enzymes working or to get their muscles ready for fast action.

But on the upside, they need so little energy that they have to take far fewer risks than warm blooded animals. Some cold blooded animals can go up to a year or even longer without food.