Marsuk

In 2043 is was discovered that Mars was, indeed, inhabited. The massive Marsuk went unnoticed for years due to its low body temperature and almost perfect camouflage. It had never shown on any satellite photos, nor early manned operations.
It is believed that the Marsuk spends alot of its time in hibernation. It was only when a mining operation disturbed their slumber that they appeared. The name Marsuk, comes from the exclamation, "Mars Sucks!" right before a few miners were eaten.
Since then, they have been a constant nuissance, eating anything, or anyone they can find. The larger question, of course, is what has the Marsuk been eating all these years before they had astronauts?