Tunneling monster

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A tunneling monster is a monster with the ability to bore tunnels through the normally solid dungeon. Tunneling monsters can tunnel through rock and closed doors, and chop down trees.

Some monsters can only tunnel through rock while wielding a pick-axe or dwarvish mattock, and through trees while wielding an axe or battle-axe. Both picks and axes suffice for doors.

Note that ANY monster that can tunnel at all can go through both rock and wood. Rock moles can eat trees and woodchucks can apparently chuck rock.

No monster can tunnel through the specially designated undiggable walls in some special levels.

If you polymorph into a naturally tunneling monster you will gain the ability to tunnel without a pick. You will still be able to use a pick, provided your new form has hands and is strong enough to carry it. Rock moles, for instance, generally cannot even lift a pick-axe. Your digging is handled separately however, even while in polyform.



When a monster tunnels through a rock wall, there is a 1/5 chance of producing the message "You hear crashing rock."[1]

Solid rock

When a monster tunnels through solid rock (the blank areas surrounding most of the dungeon), there is a 1/3 chance of some waste being produced. 1/4 of the time this waste will be a boulder, the rest of the time it will be a single rock. No message is produced.[2][3]


When a monster tunnels through a tree, there is a 1/3 chance of a random piece of fruit being produced, chosen from apple, orange, pear, banana, and eucalyptus leaf. No message is produced.[4]


When a monster tunnels through a closed door there is a 1/3 chance of producing the message "You feel an unexpected draft."[5]

Monsters capable of tunneling

Without a pick/axe

With a pick/axe


You hear crashing rock
Produced 1/5 of the time when a monster tunnels through a rock wall
You feel an unexpected draft
Produced 1/3 of the time when a monster tunnels through a door
Monster digs in.
Produced when a pet umber hulk, woodchuck, or rock mole eats something off the ground in your sight. This YAFM replaces the ordinary pet eating message.[6]

Technical details

Monsters that can tunnel have the M1_TUNNEL monster attribute. Monsters that require picks and axes also have the M1_NEEDPICK monster attribute in addition to M1_TUNNEL. No monster in vanilla NetHack has M1_NEEDPICK but NOT M1_TUNNEL.

See also