The most remarkable thing about the Alolan Diglett, as far as most biologists are concerned, is that it exists at all. The aggressive Yungoos and Meowth eagerly prey on these pokemon, and while historians are right to point out that both are introduced species, Incineroar and Decidueye were such a deadly presence in prehistoric times that the modern era must if anything be safer for wild Diglett. Even Alola's volcanic rock is tougher to dig through than the soil which covers most of the world's landmass. Although a great Dugtrio may be the World Pillar, this does not mean its descendants have successfully colonized every patch of dry land; Diglett are notoriously absent from Hoenn, Unova, and Kalos, yet have somehow made their way to these dangerous volcanic rocks.
The Alolan Diglett, of course, is no ordinary Diglett – unsurprisingly, for ordinary Diglett could never have lasted long in the wilds of Alola. Yet the three hairs on their heads which hold the key to their survival often fail to be noticed by the untrained eye (or at least the untrained foreign eye: early taxonomic works from Kanto describe only Dugtrio, like Raichu and Marowak, as possessing a separate Alolan form). The hairs are remarkably sensitive feelers, and evolution has taught Diglett to rely on their hairs as much as possible. They surface only when they are certain to be safe, often to humanity's chagrin.
For Alolans, at least in areas where Diglett are common, have learned the hard way to look carefully at the ground when they walk, lest they step on hairs with roughly the consistency of broken glass and sharp enough to slice through Tauros leather. Worse, this often prefaces a fall, for stepping on a live Diglett is no way to maintain one's footing!