Stranger yet, a search of "gay" on FurAffinity brings 78765 results, whereas a search of "straight" brings 36872 results.
It's just mind-boggling to me that heterosixuality could be the majority sixuality in the fandom, and there be more than twice as much art content in relation to gay males/females than straight males and females.
I imagine it's likely that for many "straight" artists, it doesn't occur to them to mark it as such. It's usually the case that the majority assumes that those around them are in the same group, or will already know/assume that
they are in that group. People will say "PS I'm gay" or whatever because it's still "a thing". Unless they just did something that implies otherwise, I never really see anyone specify "PS, I'm straight".
There's also the factor of people who are "unsure", or experimenting, or whatever. There's an unfair/insulting stereotype that bisixuals just haven't decided yet instead of it being a real orientation, but there
are many people out there who aren't sure of themselves, or jump to conclusions about their own feelings, etc., as it's a confusing time for many. It's possible that these people will kind of throw themselves into groups that are more "out there", and give the furry fandom an inordinately high representation of those people.