I have a number of zoo connections throughout the US and I can honestly say I know of none of them that employs someone just to do terraria - that is usually part of a larger job description. In any case, in the present economic climate you'll be hard pressed to find any zoo job. Quite a few zoos have let people go. Dallas Zoo (which is publicly owned - unlike Fort Worth Zoo), for example, is restructuring and turning over management to a private body (i.e. going commercially run) and they're having everyone presently employed re-apply for their own jobs, even the director, in an effort to cut a lot of staff.