Am I being unreasonable?

I don't think so. Tell your friend you'd like to spend time with her but you really don't feel comfortable going to a zoo.

As for those of you bashing her for being whiny or unreasonable,let's change it up a bit. A group of friends has plans to do something for one person's birthday. At the last minute, the birthday boy/girl decides to go to a strip club. One of the friends is a Christian and doesn't want to go. Would you think the Christian was unreasonable for asking that they revert to the original plans?

You're not being unreasonable. We all have our limits. I don't avoid zoos as a rule, but there are certainly zoos I myself would not feel comfortable going to. And would decline an invitation to.

Yes, it's your friend's special day. But that doesn't mean you are required to ignore all your own moral ideas. Nobody would consider it unreasonable if you for instance declined an invitation to a cock fight on your friend's special day. Or for instance a visit to a night club with exotic dancers if you consider that human exploitation. Nobody would expect you to eat a mountain of chicken at your friend's special day if you're a vegetarian. Well, your moral limit is zoos.

Just be gracious about it. Decline the invitation, but still wish them a good time.

No. If going to a zoo is against your morals, don't go. If your friend is your friend, they would understand that you don't feel comfortable going. Is your friend aware that as a ethical vegan you don't support the use of zoos?. If your friend gets in a huff over your refusal, then that is their own problem. You shouldn't have to break your morals to please a friend, and a friend shouldnt get in a huff for you not wanting to break your morals. If your friend doesnt want to change where the group goes ( which she doesnt have to if she really wants to go to a zoo) then reschedule another date where you can go out with her and do what was originally planned while she and the others do their own thing at the zoo on that day.

No, I'm not keen on the idea of zoos either. If you feel stringly I don't see anything unreasonable about deciding not to visit a zoo.

No your not being unreasonable, You don't like zoo, you have every right to decline the invitation

Your friend will understand

I think you are't unreasonable.

i don't consider it unreasonable at all. perhaps you can arrange to meet them all later or beforehand for a quick bite or drink so that they are quite sure you're not refusing their company.

You can still go just go do something else while your friends are at the zoo and meet up later. I wouldn't do something i didn't want to and a true friend would understand your absence. My only advice is to not patronize your friends for doing what they want to.

Organise something different to do with her on her birthday. If you don't feel comfortable with doing something, you shouldn't change your morality for somebody else. Just make it clear you want to do something and make an extra effort to do something with her she will enjoy.

You do realize that without high quality captive breeding programs species like the California condor and black footed ferret would have gone extinct years ago?

High quality zoos don't keep their animals to exploit them. They keep them to help species at risk not go extinct and to allow the public to see animals they wouldn't any other way. That has a huge impact on the public's support of conservation efforts. Imagine that you've never seen a lion in real life and someone asked you for a donation to help lion conservation. Because you have no actual personal connection to that species, you probably won't donate; but if you've seen them in a good zoo, lions are a much more tangible concept.

If you honestly can't/won't go to a zoo, don't go out with them. You shouldn't expect the person celebrating something to do what you want.