I don't have the books with me so I can not verify this, but I have always played that a simple perception roll can reveal the presence of a werewolf, or indeed a wolf-blooded character.
The idea being that a werewolf smells different than a human, and werewolves have an incredible beastialbestial instinct and sense of smell (combined with their primal urge) they should be able to instinctively know that other werewolves are nearby at least.