Put pure spearmint and peppermint oils around the holes as well. Mice hat that smell, apparently.
An effective mouse repellant is also snakes, live or dead. Many years ago, a friend and I were growing weed in a rather desolate part of the hills around Lake Berryessa in central California. In order to facilitate watering the plants in the very dry summer, we found an isolated stream in the spring and located a turn in the stream around a boulder. This formed a natural place to grow the plants. Up stream, we installed a waterbed bladder that we funneled water from the stream into to act as a resevoir. In late spring, the stream dried up and the stream bed turn was rich with soil suitable for growing weed. We cleared the land of plants* and planted established weed seedlings (from special Afghani tiger striped seeds!) and set up a drip feed from the waterbed into the soil. We then left them for a week.
We would return every weekend to check on progress. The spot was extremely well hidden. We had to drive towards the dam, park in a secluded spot. Swim across a river, hike up a very steep hill, negotiate through a briar patch, up another hill and around a steep bend. Quite exhausting but it worked as no one found the weed plants that whole summer. But on subsequent visits, we noticed something was nibbling on weed plants! Deer! the hills were drying out and the weed plants were one of the few green plants around thanks to the drip feeding. So we built a fence around the weed plants using fallen branches and some plastic netting. This kept the deer out.
Then another visit we noticed something else had been nibbling on the plants. Field mice! The little buggers were eating the shoots which is where the buds are formed. the fence mesh was too big to keep the mice out. We decided to find smaller mesh to combat the problem. We searched around but couldn't find any during the week so we went back to check on the damage to the weed plants the following week. But when we got there we found a huge rattlesnake wedged in fence! We deduced the snake had gorged himself on field mice attracted to the weed plants and then had got himself stuck in the fence. Looking at his body he looked like he had a least 2 mice in him. He then somehow died wedged in the fence. We simply left the snake there. The next visit we noticed no damage had occured to the plants as the dead snake seemed to scare away the field mice while the fence kept the deer away.
As the summer continued on, the hills turned golden brown but our little weed patch stayed green from the waterbed bladder and the plants grew very well. Soon it was harvest time and my was that afghani bud amazing. It was so stick a joint would clog up halfway through. You had to smoke it in a pipe you could clean easy as the resin was so thick.
*remind me to tell you about getting poison oak over 90% of my body from this
So get yourself a rubber snake and some spearmint oil (available from Fresh and Wild in Soho)
http://www.wholefoodsmarket.com/UK/soho/index.html
But I was so hysterical at the time, I didn't really care about the money and had to get rid of the mice at all costs.
