It's bad enough that even South Park can make jokes about "two gay dogs" and everyone laughs, and the same motif shows up in other pop culture. It happens regularly enough that it's become a joke.
There is also sexual activity in various species including simians that would be labeled as "homosexual," with perhaps some of the behaviors serving some sort of social purpose.
There is homosexual behavior in humans (which could involve sex used for purposes other than romance, such as to threaten or intimidate or just to pleasure oneself); then there is "homosexual romance" that also involves homosexual behaviors that is leading to the arguments about gay marriage; and I'm not sure what the connection is between those two activities and homosexual behavior in the animal kingdom, but yes, various species have been involved participating in "homosexual behavior."
Probably the same way "new discoveries!" are made in the religious scientific/historical world all the time that supposedly support the view in question. We can't really prejudge the quality of the claim until we research it, but in anthropological studies and animal behavior that occurs far from civilization, there's usually not much reason for it to flow into public consciousness unless there's a public cause driving it. The scientists are just tracking the behavior; it takes someone else who finds the information useful to promote it, otherwise it just ends up in the lab notes and science journals.Could this be a new argument devised in the argument? Years ago, I saw one pro-gay book trying to argue from nature have to appeal to other life forms such as many plants and perhaps lower animal forms to try to prove nature favors it. Now, all of a sudden, where are they getting these claims with all of these other, more developed animals from?
Take it on a case by case, I guess.