Gores are airborne creatures presumably composed of the molten rock or a similar substance and thrive on the planet of Solar. Their only means of attack are by following ships that enter Solar's gravitational pull.
Up until Star Fox Command, it was presumed that the Gores were the only "living" beings on Solar, but this was proven wrong in the DS title as many creatures had been introduced. However, since there is some debate over whether or not Star Fox Command is canon, this may or may not be so.
Whether or not the Gores are natural wildlife to Solar or experiments created by Andross remains undisclosed.