Do things despawn on boats or in houses after some time? Or are they getting killed?
I'm fine with both, I just wanna know which is the case.

Unattended pack horses, pirate parrots on boats, things like that...seem to vanish after some time.
What's the cause of it? I'm leaning toward despawning since I tried some really remote places to test this and it still happened.
But, player dedication is also a thing. So yeah. I'm curious.

I believe untamed creatures disappear after 40 hours. Otherwise, if tamed, they're dead.

That must be it, then...cause the pack horse should have been safe...theoretically.
Thanks.

Untamed animals despawn like capitalist says, unless targeted by something. I used to keep a bunch of untamed dragons in a keep and would just cast mass bless on them to keep them around.

Is there still a shortage of stable slots? Best bet is to stable them if you want to keep them.

I see. Thanks for the tip with the targeting.

Stable slots I don't know much about, I have ever only tried the stable in Trinsic and it seemed quite spacious.
I was mostly curious about (pack) horses and small pets like birds. They're abundant but the fact that they disappeared from houses made me curious.

so I could mass curse all my sheep once per day, and it would keep them there, versus re-taming them every day?

Yes, test it on one sheep if you're wary.