[alwaysdoit]

Does the animal's lifespan matter? Intuitively it seems like killing something that will only live for a few days or weeks at most matters less. So I'm not sure it's all due to "cultural worth" (though I don't disagree that's part of it).

[orthecreedence]

Yeah, I've thought about that too, actually. And certainly, I feel better about killing any animal that I perceived to have had a "full life" (dogs included).

I tend to think that lifetimes are measured in lifetimes (relative scale) by various animals. So where a fly might live four of our weeks, to that fly, perhaps it was perceived as a good 60 years time if it was on our scale.

So to me, lifespan doesn't factor into it too much, although perhaps you're right that that is another piece of data used by people to measure an animal's "worth."