As mentioned above, he tends to be fairly intelligent, often suggesting legitimate solutions that help get Zav and the others out of tough situations. Of course, as mentioned, Zav may very well simply be misinterprating what he's saying. Judging purely off the tone of his gurgles, he tends to often seem irritated or upset over whatever situation he's gotten himself in.
When Calmar was hatched from an egg, it was quickly discovered he could only communicate via gurgling noises. His blaargian parents were horrified, knowing it meant he may not be able to say Blaarg or properly worship the hat gods, but assumed he would grow out of it. He didn't, and they were order by authorities to "banish" him (ie abandon him on a nearby space station.) They reluctantly did so, and he spent much of his life fending for himself there, which mostly amounted to stealing food from the cafeteria. How he feels about any of this, if he even cares at all, is only known to him.
He was later found by Zav, who offered him adventure, money, food, and possibly a nice place to stay down the line. Zav took him following him around as a yes, and he has been with him ever since.
Zav is the only one who seems to have any idea what he's trying to say, though it's ambigous whether he actually understands him. At times he seems to interpret him in certain ways for his own benefit.