Are these holes attached to a tunnel system or are they burying holes? Shews could be a possibility if they have tunnels, and there are a wide assortment of little digging critters, such as chipmunks, voles, etc. 2 " is too large for them to be made by any of the solitary wasps, or earthworms, so I'm thinking 4 legged critter here.

It sounds a lot like gophers to me. They'll have the main entrance holes which are the classic hole with all the dirt piled in a "crescent" to one side of a plugged hole. However, along the runs they'll make "pop" holes. They just pop up (imagine that) and feed on grass and other herbacious plants / weeds around the hole, go back into the run, and move along. Many times juvenile gophers in particular will not plug these holes back up (Hence the 2" diameter rather than something a bit larger). Look for signs of feeding around the holes if you can get to them before your dog does and if you find it, you can be fairly certain it's gophers.

Or, perhaps voles, aka meadow mice.

page, I am also in So. Ca. I am thinking like me you have pocket gophers. They pop their heads out some but I have never seen them come out. I am in Moreno valley, riverside County. We fight these each spring cause the neighbors have dirt yards and we have a lot of grass. Now this year they are working in the field out back with heavy equipment and driving them this way. The neighbor dog grabbs them and kills them...does not eat them. Our cat has caught some. Your dog is just reacting to the noise under ground and 'hunting' Put a search in on the Garden Web forum and put in Gophers and see what all they are doing to be rid of them. We are down to two now. One in the front is a "Caddy Shack" contender. We have done poison, gopher flares, road flares, castor oil, chewing gum. No luck yet. I need to kill it and not chase it to a neighbor and have them chase it back. June

Try pouring human urine around the entrance. It works with a number of other burrowers and could work here too.

Here is a link that might be useful: Getting rid of groundhogs and other burrowers

janetr: urine will kill everything around it.

Here is a link that might be useful: holes in lawn