Portable recorder + the zoo - if you go in the early afternoon on a weekday when there are less people and talk to the staff about what you're doing, some times they'll be really cool and let you go to the more secluded sections to record. You can also ask what the feeding times are, and they're usually happy to say. Animals tend to be more vocal during feeding time.
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giraffes rarely make any sound, i don't think there are libraries with giraffe vocalisations.
I ended up finding all of them via a lot more searching. As for the giraffe, apparently they make noise that is too low for human hearing. However, if you get a baby and it's a bit scared, wallah we have something! A bit of RX and editing made it work for my project. In case you wanna see... http://www.youtube.com/watch?v=Y7iuOZVJhs0