In nature, conflict and cooperation are prevalent not only between individuals of the same species, as discussed in Chapters 2–4, but also between individuals belonging to different species. If thinking of interspecific relations, what perhaps first crosses one’s mind are the salient relations between predators and prey, or between parasites and hosts. However, different organisms also cooperate with each other, which in fact may lead to entirely new organisms (Kiers & West 2015). Here we focus on the behavioural responses of individuals to competition with individuals of other species, based on the concepts we outlined in the introduction to this book: non-interference rivalry (race), conflict (fight), or cooperation (share).