Dukino is the subject of three animal rescue missions in Lynchwood, Medicine, Food, and Shelter. He is the son of a huge skag appropriately named Dukino's Mom (which can be killed during the mission Demon Hunter after helping Dukino) and the grandson of an even bigger skag, Skagzilla, appearing in Borderlands.
When Dukino is first seen, he is a tiny, wounded skag sleeping in front of his tiny cell. His three missions in succession lead back through Lynchwood and finally to an old mine where he stops to sleep.
Later acceptance of the mission Demon Hunter draws the Vault Hunters back to the old mine, now occupied by Dukino's mother. Dispatching the giant skag is a feat graciously rewarded by Dukino.