From your description—a huge tunnel under concrete—it’s almost certainly a burrowing animal rather than insects. Here’s a breakdown of likely culprits:
1. Likely Animals
- Moles
- Small, burrowing mammals that dig tunnels for insects.
- Usually create raised ridges or molehills rather than huge, deep tunnels under concrete.
- Groundhogs / Woodchucks
- Can dig large, deep burrows under structures.
- May eat garden plants.
- Rats (Brown rats / Norway rats)
- Dig tunnels along foundations for shelter.
- Can gnaw through concrete edges or soft soil under slabs.
- Signs: droppings, gnaw marks, grease marks along walls.
- Pocket gophers
- Create extensive underground tunnels with mounds of dirt.
- Usually more noticeable in lawns or gardens than directly under slabs.
2. Signs to Confirm the Culprit
- Soil piles near openings: Small piles → moles; larger piles → gophers, groundhogs, or rats.
- Damage to structures: Cracked concrete or sagging slabs → larger rodents like rats or groundhogs.
- Nocturnal activity: Rats and some rodents are mostly active at night.
- Vegetation damage: Plants eaten or uprooted points to herbivorous burrowers like gophers or groundhogs.
3. What You Can Do
- Inspect the tunnel entrance to check size and type of soil displacement.
- Set up motion-activated cameras to identify the animal.
- Seal off tunnel access carefully (after the animal is removed) to prevent re-entry.
- Consult a professional pest or wildlife control service if the tunnel threatens foundations or plumbing.
Given that the tunnel is under concrete, I’d suspect rats or groundhogs, as moles usually don’t burrow that deep under slabs.
I can make a step-by-step plan to safely identify and stop whatever is digging under your concrete, including traps and barrier methods.
Do you want me to do that?
