Besides these creatures, what other burrowing monsters leave a tunnel behind?

Question

I'm looking into burrowing creatures that can leave a tunnel behind.

Movement, Burrow:

A creature with a burrow speed can tunnel through dirt, but not through rock unless the descriptive text says otherwise. Creatures cannot charge or run while burrowing. Most burrowing creatures do not leave behind tunnels other creatures can use (either because the material they tunnel through fills in behind them or because they do not actually dislocate any material when burrowing); see the individual creature descriptions for details.

So far I've found these that specifically state a tunnel is left behind:

• Dire Badger
• Thoqqua - says so in MM.
• Umber Hulk

What other burrowers from the Monster Manuals can leave a tunnel behind?

Preference for ones useable through high level [feat-enhanced] wild shape or shapechange

Answer 1

Some options:

Ankheg (MM I)

A burrowing ankheg usually does not make a usable tunnel, but can construct a tunnel

Delver (MM I)

A delver burrowing through stone leaves behind a usable tunnel about 10 feet in diameter.

Frost worm (MM I)

A frost worm cannot burrow through stone, but can manage ice and frozen earth. When moving through such hard materials it leaves behind a usable tunnel about 5 feet in diameter.

Garngrath (MM V)

They burrow into the mass of matter that makes up the plane’s ground, adding to the innumerable tunnels therein.

It's not explicit, but since they "add to tunnels", it means they can at least opt to leave a tunnel

Mockery Monarch (MM V)

Their burrows produce tunnels only if they choose to create such openings

Answer 2

There are two factors to consider as they interact:

• The nature of the ground being tunneled through

• The nature of the creature doing the digging

To the first point, some types of ground are really bad for leaving a tunnel behind. Sand, for instance. Shai-Hulud probably doesn't leave much tunnel. Rock, on the other hand, is probably great for leaving one, if your critter can actually cut through it. (That said, look at mines; they tend to need artificial bracing built to protect the ceiling from collapse)

The other factor is your creature. There will be ... "bands" or types of creatures with similar tunnel-leaving characteristics.

• Small creatures have an advantage, as smaller tunnels have less unsupported ceiling. Think moles, foxes, kender. (Or big creatures with a small cross section, like a snake)

• Gooey creatures have an advantage in softer soils, as their putrescent drippings can bind to the loose soil, at least temporarily bracing it. Think gelatinous cube, (maybe?) purple worm.

• Hot creatures have an advantage, as they at least partially melt through their medium instead of battering through it. Less jarring. And the medium can partially self-heal in their wake. Think remorhaz (for ice), lava elementals (for rock).

• Smart creatures have the hugest advantage, as they know what they're doing. They will avoid "bad rock", dig in the best places, and shore up any weak points. Think dwarfs, svirfneblin.

Answer 3

It's probably a safe bet that any creature which actually digs through the ground, as opposed to "phasing" through rock like some creatures from the Plane of Earth can, will leave a gap behind. Whether that gap lasts for seconds, hours, weeks or forever will depend on the material being dug through, as per the previous post.