We just went snorkeling with stingrays in the Bahamas, and they had the same thing happen. The enclosure was only females, and yet one of them has gotten pregnant.

I assumed she was pregnant when the put them in the enclosure and they didn’t know it? Or that they weren’t as good at distinguishing male/female as they thought they were.

But you know, maybe there are some cool optional hermaphroditic traits in sting rays that biologists are just currently unaware of.