The snake is a resident of the jungle.
In "Tracker Joins the Pups!", Tracker bravely saves Carlos from the snake. The snake reappears in "Parroting Pups".
Tracker calls the snake Señor Serpiente ("Mr. Snake" in English). She is later revealed to be female because she had babies, so Tracker was mistaken when he addressed her as a male. However in Pups Jungle Trouble, after Marshall thought she was a vine, Carlos said, "Don't worry, Marshall. HE'S a friendly snake." It's unknown if each snake is a different snake. At least the one in Jungle Trouble because it was a different color than the other two. And the other two snakes weren't friendly.
The snake is light green with yellow lips and a long pink tongue.