Okay, so, here’s the thing about predators:
When we look at them and go “Oh my fucking god, how do they do [this thing] without fucking getting [terrible consequence]?!”, what we are forgetting is that animals in general fuck up just as much as we do.
So we’re like staring at some documentary of lions taking down a goddamn elephant and going “Jesus Christ, lions are terrifying, how do they take down an elephant without getting trampled?”, the answer is “Some of them get trampled like whoa.”
So, great horned owls can, and sometimes do, wind up with quills stuck in them (feet, faces, chest, wing—we’ve found owls with quills pretty much everywhere an owl can get quilled) when they fuck with porcupines. Much like fisher cats, though, owls go in for a face-strike, where porcupines are pretty much unprotected. Unlike fisher cats, owls usually have the benefit of surprise going for them.
Thanks to their huge fuck-off doom-bird feet, great horned owls’ preferred murder methodology is a sharp killing strike that takes prey unawares and is immediately lethal. They’re well-camouflaged and their flight is silent, so they’d preferentially be hitting a porcupine that doesn’t know it’s there. A porcupine that doesn’t know it’s there is a porcupine that doesn’t have its quills up, which makes avoiding them way easier. This is kind of the same way they prey on skunks like bonkers skunk-eating machines. A skunk that goes from tooling around doing skunk things to dead before it knows what hit it (an owl) is a skunk that doesn’t have time to unload the ass-cannons.
If a first strike doesn’t kill the porcupine, the owl has the option of fucking off to kill something else if it’s not that hungry, or it can swoop back around to try and finish the job with another strike to the face at greater risk of running afoul of the porcupine’s defenses.
I mean, if I was a great horned owl, I’d totally upset the porcupine into climbing a tree (one of its predator-defense mechanisms), pop that motherfucker right off its perch (the owls’ preferred method for preying on other raptors), and then eat it once it was dead or out of commission (porcupines aren’t great at falling from heights because they usually don’t need to be). But that’s a pretty complex predation behavior for an animal to come up with for a prey item that doesn’t comprise a substantial portion of its lifetime take, you know?
I mean, they’re not fucking lammergeiers, here.