Voles tunneling in 3x8 foot garden boxes
I think they are voles. The holes are about an inch a and a half in diameter, and go a few inches down, then seem to branch out. They tunnel through my 3x8 foot vegetable garden beds (these are four sided, about two and a half feet deep) that are planted with chard, kale, beans, peas, zucchinis. Then the plants die for lack of water if I don't catch them in time and push the soil down. Even so, some of the plants die. Maybe they are also disturbing the roots. I can dig out the beds and put down hardware cloth wire, but they seem to be coming into the beds from the top. I hate the idea of using poison. I put out mouse traps, and I do catch a lot of mice--and I know they are mice. They have big ears and long tails. Do mice dig tunnels? I am desperate, driven to tears. My winter garden is in tatters. I lost almost all my beans earlier this summer. I live close to the national forest on the southern Oregon coast, my house is surrounded by forest, and I see many of these same holes all around the house. The only place I care about is the garden. They can have the rest.
From the hole size, it does sound like it could be voles/meadow mice. These are short-eared, short-tailed rodents. Mice may be using tunnels as burrows. I'd continue using your traps to try to reduce numbers.
To deter voles/mice, you should also remove any vegetation or woodpiles/debris around the raised beds that rodents could be using as cover.
At the end of your growing season, I'd concur that you should dig out the beds and line the bottoms with 1/4 inch mesh hardware cloth. That would stop them from burrowing in from below. For now, I'd also try installing a 1/4 inch mesh hardware cloth fence (12-18 inches above the ground) all around each raised bed. This may deter the voles from entering the raised beds.