Thats true, but Im really wondering more about animals that would be transgendered in a way thats parallel to humans, not those that can change at will or based on environmental conditions
Animals for the most part dont even have complicated emotions like guilt and pride. Gender and gender roles arent the same for humans, but to an animals more simplistic mind they might as well be, so any animal that behaves in the role the opposite sex does would be the human equivalent of transgender. And also, environmental conditions and changing at will arent exceptions. Humans dont have them currently but if there are rays or mutations that can change the brain or the body found in the future that would also be transgender. Actually, in the tvtropes page I listed, 5-ARD counts.
Interesting points, and largely along the lines of what I was thinking originally. I just wonder if theres any known examples or research that has been done in the area.