If they are 2'' holes, and ground squirrels, rat pellets wont work. Use sonic spikes, they are long-term solution. Biggest thing to put into consideration, is the extensiveness of the burrow. You can have a colony stretching several miles with linked tunnels and never know it.
If you want to keep them away/out, than use sonic spikes. Stick them in the ground and forget.
However, if it's snakes, than, well.............................................. ........ You have a bigger problem than you ever thought. Ground Squirrels are big on the snake diet. If those are snake holes, which would also fit the ground squirrel pattern, you need to identify the snake. If it's a poisonous species, get some ammonium nitrate, connect it to a battery pack for a garage door opener, about 1oz should do it, and rig it to a trip wire. Gets rid of the snake, and reseals the hole at the same time!
Last edited by GarrettFiveZero; 02-18-2013 at 05:38 PM.
It is hard to imagine a creature less intrusive than a chipmunk. Instead of pouring poison(!) into your garden, you could take the position that local wildlife is actually a net positive, and something that should be encouraged. Best part? - you don't have to do anything. Just leave it alone.