I have to agree with everyone else who spoke down on those two things. I didn't even know much about this "Plague Dogs", and only know very little about "Felidae", but from what others have said, they sound like they'd be horrible additions to the site, totally out of keeping with the family-friendly nature of it, and not visited much at all but by the few people who seem to be that interested (which is a problem on several source sites right now, actually).

Plague Dogs is too violent, and Felidae is mature AND violent. There might be Sources for the older members on the site, Ginga, Watership, etc., but this is still a kid-friendly site. I'd never even heard of these animations until about two years ago. I never stepped foot into either fandoms due to how mature they were.

Bringing these to the Sources wouldn't be very wise, and as Troll said, I doubt either would get activity. The other Sources similar may have warnings about their content, but these two animations are far from a small warning.

I remember I ran into a Plague Dogs scene where a man is shot in the face by one of the dogs. And, yes, there was a (censored) scene in Felidae. This content is just too much for the site to be handled.

There would probably just be more arguments about it than there were for any Sources in the past. It's simply not a good idea.

IF you want a somewhat darker story I would recommend The Secret of NIMH, which does have a Source. The Redwall books are also pretty grim at times, especially Rakkety Tam, though the cartoon show was considerably brighter and did not include Rakkety Tam. It was still pretty good, and I would even go so far as to say that most of the changes I noticed were beneficial, but if you prefer dark plots as a rule you might disagree.

I also heartily agree that there should never be a Felidae Source. Even as an adult I've made a firm decision never to watch that movie (I've already got too many movies I wish I could wipe from my mind for far lesser issues), and I agree that it has no place on AS. I do not know enough about Plague Dogs to comment, but from what I've seen said here I am not at all inclined to dispute the thought that it should not have a Source either.

I would actually be interested in a Plague Dog source, I mean, I do agree that it probably wouldn't be that "active."

Not to mention I see no activity potential for Plague Dogs source....

Plague Dogs, maybe. Felidae, no.

Watership Down is different in a way because there was a version of it that was directed as a family friendly series. This was the TV series. The original movie had scenes in it that were not, and even now aren't, suitable for young children. I realized this when I first watched the film when I was really young, because these scenes disturbed me. Yet, I do still very much enjoy the film.

Plague Dogs, while made by the same author as Watership Down, subjects very disturbing material. And while it probably could make an alright source site, like with Watership Down and Ginga, there would have to be a warning to the blood.

Now, that leaves us with Felidae. Me personally, highly disagree that this film should ever see the light of day as a source site. This film. Was not. Intended. For young audiences. At all. And I simply can not stress this fact enough. When I first watched this movie, I remember being perturbed to the point that I was visibly shaken, and I was a teenager at the time. The sources are meant to family friendly sites, places where young children go to enjoy the movies featured, and Felidae simply is not, and never will be, a family friendly movie. It just simply isn't.

Watership Down was an exception because after all it was a children's book and it had a child-friendly TV show remake, but not every movie that is animated and has animals in it is meant for children. Especially Felidae that has murders, swears a lot of (censored) references and even a (censored) scene.
Those movies are absolutely not meant for Animation Source.