All the organisms are as a matter of fact intelligent; and I cannot think of an organism that lacks intelligence. This however puts forward the question of how one defines intelligence.

For me, intelligence (at the level of an organism) is the ability to percieve internal and external cues, computete them and react accordingly to ensure the organism's survival and well-being. As such therefore, all organisms capable of surviving have intelligence.

Maybe you think of intelligence as the development of consciousness or one's ability to realise its own existence (as we humans certainly do and have limited evidence that other animals also do to some extend)?