We do what any living thing would do given the chance. We try to outcompete and outconsume the competition because that's what evolution selects for. The universe has a tendency to form dissipative structures that increase entropy the fastest, and we are a result of that. Sure, Skynet or somesuch dystopian sci-fi ai wouldn't be the product of evolution and as such wouldn't be immediately predisposed to similar behaviour, but as soon as a competetive situation is introduced, that's what you get.