As Target said, this is in general very tricky with all different animal names (or any names for that matter) in one (or even more) languages and dialects. The suggestion you put forward is possible as a Challenge Checker can read information from a bookmark list and check against it. But this means you have to manually select all caches that qualify and keep the list up to date. Could be quite a lot of work. Probably it is easier for the geocacher to go through his/her found list manually, as he/she knows the lingual oddities the best.