When a Yoshi jumps on a Little Skull Mouser's head, hits it with an egg, or spits an enemy at it, the skull it is wearing crumbles, turning the creature into a normal Little Mouser. Unlike many other small enemies, a Little Skull Mouser cannot be defeated immediately by a Ground Pound; instead, the attack has the same effect on it as a normal jump, merely destroying the skull on its head.
In Yoshi's New Island, Little Skull Mousers appear in Bandit Valley.