The ability must be trigered by the Player. While the units perfoms in, it will burrow itself underground, leaving only a little mountain of dirt still visible. Burrowing units cannot attack. Digging works very similarly to Camouflage. Digging units cannot be detected by most enemy units, but can still be detected by those with Keen Sense and Sonar Pulse abilities, and structures like Soundbeam Towers. While underground, units recieve 50% less damage from attacks, can only see 10% of their full Sight Radius and regenerate Endurance and Health slower. Many other abilities are disabled while underground, but Inherent effects, like Immunity, still works. Sonar Pulse still can be used.
Digging is not present in an entire classification. Instead, some particullar animals have this abbility.
Digging units can be used to scout unexplored areas and to spot some enemy structures' location. Also they can used to kill some smaller groups of enemies.
As camouflaged units, digging units may be discovered if passing to close to enemies and they are easier discovered than camouflaged. So is recommended when scouting an enemy base to keep theese units away from confrontation with any enemy unit.