You can make your own roleplay about it. It may take people time to answer and join though. You should use the search feature to see if there is one if you don't want to make one. If you do make one, here are a few tips:
You should have some type of plot. Just saying "We are two packs of wolves in the forest. Okay, go!", for example, won't attract people. You should put down a basic idea of where to go, without saying how everything will end.
Good:
There are two rival packs in the forest. Food is becoming scarce as people destroy their home. One pack wants to kill the invaders. The other pack wants to run and find a new home. Neither pack is big enough to do what they want. They will need to come together, but which road will they choose?
Bad:
There are two rival packs in the forest. Food is becoming scarce as people destroy their home. One pack wants to kill the invaders. The other pack wants to run and find a new home. Neither pack is big enough to do what they want. They will need to come together, and run. Hopefully the good pack will beat the bad pack.
The bad example sets it up for which one you want to win, instead of letting it happen normally. Granted you aren't talking about wolves, but it was the first example I thought of.
You also need a title that makes people want to join. "~~~~~~WARRIOR CATZ!~~~~~~~~" is not an effective title. "Which Pack will Survive?" is a bit better. It makes you curious to see what it is about. Also, try to put what it is in the title. "Survival" isn't very good because it is about the survival of what? If you do something like that I suggest something more like "Survival - Wolf Action RP" because it says what it is. If a person likes wolf RPs they will be more likely to look at it.
A good form to join actually does make a difference. I have been known to walk away from an RP that either had almost nothing on a form, and too much. Asking a wolfs favorite color is silly (again, dramatic, but you get my point), but not asking about their personality is also a problem.
The level of the RP also makes a difference, but it is hard to control this factor. Nobody likes RPs that have only new people. Posts like "I walk over to you and start to yell at you." are never fun. But most people here aren't literate RP'ers either. Semi-lit or experienced roleplays are where most people feel comfortable.
Putting a
small link or banner in your sig I have found to be best for advertising. Making them sparkle or animated seem to drive people away. It is a bit like an obnoxious title in my eyes. A simple banner or link that has the RP's title on it, is usually more interesting.