Using it on a website does not fall under fair use. The educational exception is much narrower than that. You can't just grab someone else's pictures and say you are using them for educational purposes. It is more for institutions and professional educators. You have even less legal ground to stand on if you just happen to also sell animals that are the same species as the photographs.
There has been a rash of people stealing pictures, sometimes stripping off watermarks and passing the photo off as their own. Whenever I see this, I let the owner know that their work has been stolen.
Those great photos take a lot of time effort and money. Is is unethical and unacceptable that someone else would post it on their website, even when credit is given.