Yes, those are vole tunnels/trails. Moles are strictly UNDER the ground, and quite a bit wider tunnels. Moles are generally not active in the winter. Voles are active all year around, and actually make the runs right at the ground's surface, just at the base of the sod.

They may or may not attack fruit trees, depending upon how hungry they are, what other food sources are around, and their individual tastes. Hard to get rid of entirely, but it does help some to put out poison bait blocks or pellets in locations where voles and nothing else can get to them (such as under an overturned coffee can with a small entrance hole cut out of the rim, weighted with a rock).

Voles. I had numerous infestations, brought in part by my habit of mulching heavily. My method has always been rat poison where their tunnels are an inch or two under. Punch a hole with your finger, pour the poison, close (tells you how good the soil is in my raised beds). They will go after your small trees, without a doubt, and in my case they ruined a Centennial crabapple amongst other trees. But if you have hardware cloth, that is the best you can do. Any damage yet?

Thanks Dennis, Glib-
Yep, that makes sense. I've also mulched quite a bit back there. No real damage yet... just a few holes and some trails that you see in the edge of the grass.

I was actually shoveling a snow pile the other day and picked one up inadvertently. I think I was surprised as he was.

I'll probably get some bait this week. Thanks guys.
-Glenn

I've seen less damage if I put lava rock in planting holes, under and around the roots of the plants. I started this after reading about Permatil, a rough soil additive that digging animals don't like.

I've lost a number of fruit trees, even a large one. I find also that running a water hose for several hours under the affected tree can sometimes save it, I assume by drowning the attackers, or maybe the roots recover better with lots of water?

It depends on the soil. In my sandy soil, with a little undulation, you can let the hose run for hours, it does not matter. The water will drain into the soil faster than you can pour it, and they can probably move to higher ground and come back in the garden after. I have also read where they can put up a plug in their tunnels very quickly.

I have also read of breaking glass bottles into small pieces, and mixing them in the planting hole, to discourage gophers.

Both moles and voles are active through winter. Moles do not hibernate and cannot store fat. Moles do sometimes dig deeper in the winter. Around here at least, true vole tunnels are hard to spot. Mole tunnels disturb the soil more and are easy to spot. Voles frequently use mole tunnels. If the trails you have are only in the grass and not a result of the soil being pushed upwards, then I'd say it is a result of voles, and as Glib noted, given time, they are likely to cause damage to your trees.

On a related thought, does anyone have ideas, opinions, or knowledge of how something like lava rock or PermaTill would affect tree root growth. I'm not thinking about drainage issues, but other effects on root growth.