Course of Action

A huge bombshell had exploded in Rui's mind. Suddenly, everything from before was starting to make sense if what Rui was beginning to suspect was true. It was all starting to click.

The lack of footprint trails incoming and exiting the area of the hunt despite the fact that smaller and lighter creatures had footprints incoming and outgoing out of the area. Then the presence of its footprints around the carcasses. It's impressive elusiveness, being able to appear and disappear in and out of an environment far too easily and inscrutably.

All of this could be explained if the creature was primarily subterranean or is primary mode of transport was subterranean fundamentally!

This wasn't an absurd notion. Even on Earth, subterranean fauna was found worldwide and included representatives of many animal groups, mostly arthropods and other invertebrates. However, there was a number of vertebrates, although they were less common.