Query for the collective brain: Animal Companion Books.
Hey Leila! My friend is looking for books with animal companions who, very importantly, don't die. Both Google and my own knowledge are failing me, so I thought I'd reach out to you and your audience, if possible!
I don't know what age range/reading level/genre you need, but the two that immediately spring to mind are Kate DiCamillo's Because of Winn-Dixie and Robin McKinley's The Blue Sword (Tsornin and Narknon both make it through BATTLE, even!).
There are loads of animals in Diana Wynne Jones' Dark Lord of Derkholm (some talking, some not), and the vast majority of them make it through.
I haven't read Michael Northrop's upcoming Rotten yet, but my fingers are crossed, crossed, CROSSED that the dog on the cover will survive.
Big SPOILER about Erin Bow's Plain Kate: Taggle the cat technically makes it through alive, but only after dying and being resurrected and losing the ability to talk. As it made me cry harder than any other animal book I've ever read (with the possible exception of each little bird that sings), you might want to steer clear. END SPOILER.
Oh, and in Eliot Schrefer's Endangered (SPOILERS), Otto the bonobo makes it through, though lots of the secondary bonobos don't. END SPOILERS.
And while it's not really an animal book, Gordon Korman's No More Dead Dogs might be a good pick, as it's super-funny and asks the age-old question: WHY ON EARTH DO ALL OF THE ANIMALS IN AWARD-WINNER BOOKS HAVE TO CROAK?
Now it's up to you, guys! What are some others?