Question: I noticed a few piles of soil near plants in the garden. Not sure which critter is doing it. 

[![enter image description here](https://i.stack.imgur.com/m4POz.jpg)](https://i.stack.imgur.com/m4POz.jpg)
[![enter image description here](https://i.stack.imgur.com/FBbSB.jpg)](https://i.stack.imgur.com/FBbSB.jpg)

So far I have not seen any damage to the plants. But I'm wondering if this critter will cause any root damage. How to guard my plants against critters like these?

Answer: 
Your location would be helpful here, but it appears that whatever it was is after insects, etc, that are living in the decomposing mulch layer (not plants). If it's not rodents, it could be possums, coons, etc rooting through. It looks to me more like something rooting, rather than a rodent tunneling. The best way to stop this (in my experience), is to catch them in a live trap, and transport them to another location. I wouldn't worry about it so long as they aren't doing any damage to your plants. Also, it looks like pretty much all the turned up layer was decomposing mulch, so that shouldn't harm plant roots growing in the soil below.
This all depends on location of course. This looks like squirrel gopher. Larger than vole and shrews. Usually the preferred food are grubs. Occasionally they will eat roots, bulbs and tender plants as well. If you don't have a big community of grubs. Echnerwal's opinion to 'wait and see' is wise. 

J. Musser's live trap thingy is good...I like it but I have to say, when you remove a critter it only opens up a new niche in your environment for a few others to come and fight over it or fill it. Tide goes out tide comes in. Killing these survivalist species is just silly. 

It has been proven that once an environment is compromised with poison and traps somehow that is translated into larger litters, more babies per pregnancy. The trick is to design and expect your garden to fit within the existing environment...a harmony. 

These underground animals are wonderful in my opinion. I don't mind 'feeding' them at all. What they do for the aeration of your soil, top dressing of lawns and controlling other insects that without that control will become far worse on your plants than loosing a few to these wonderful, FREE, laborers. A little raking and a few plants that die from root damage or root exposure or eaten is a small price to pay. 

There are Rodent Killing Killers Sites I've been harassing, mostly cause I inserted some common sense and the killers themselves became incensed and harassed me! The internet is a wonderful thing...grins!! I have never ever found it necessary to kill a mammal, even mice. Heck, most insects are welcome as they also control harmony. Remember, when you kill something you are opening a niche for more to come into your environment. If you can learn about your new 'family' members you stand a chance to figure out a way to create harmony. Humans are so arrogant. We think if we kill a little shrew that will 'save' our gardens and make sure we are in charge. Ha ha. If we don't understand the system there is no way we are going to make things better by killing