Human beings are the only intelligent life in the universe?

We, human being had believed for a long time that we are the only organism can think, speak, write and communicate in the world or even space. However, these days many studies suggest the possibility that some of other animals are also really intelligent like apes, crows and cetaceans. Personally, I have read the report about intelligence of dolphins and I found they have many similarities with human beings.
First of all, they can communicate each other with supersonic waves. They are helping each other by using this ability. The report also said there were many cases that dolphins had saved humans. One of the cases, is that dolphins reascued a boy who was attacked by a shark.
To my surprise, human beings and dolphins are also alike in bad ways. Dolphins are so sentive just like us, and it often happens a dolphin commit suicide due to the stress. For example, in Janurary, newspaper publicized the case that a mother dolphin killed herself after she was separated from her baby in Wakayama.
For the reasons I menioned above, I cannnot belive that human beings are the only intelligent life in the universe and I want studies in these field to advance more and more.