I had the same aggrivation with the garden as last summer.  Each time I planted new cabbage the ground hogs would break in and eat everything down to nothing.  My son and I had priced out traps, they always ran about $80 but at our local Quality Farm and Fleet there was a sale for two sizes of traps for $35.  Bing Botta Boom, it finally solved our problem.  We even caught two skunks the following two nights.  It was a great plan to get them out with out being sprayed.