While Wildmutt is an alien who can't talk, he does make snarls, grunts and howls like any other dog. 

This dog-like alien runs on all fours, can climb on the toughest surfaces and can pierce through the hardest materials with his sharp claws! Wildmutt can use his sensing abilities to his advantage by tracking down the enemy with their scent and surprise them with sneak attacks! Wildmutt, being dog like can also tend to act like a dog, which gives Ethan both ups and downs.

Wildmutt is in a majority of episodes in Season 1.