After some investigation, a gopher tunnel was discovered in the ground underneath where we planted seeds. Sneaky!
Here is one suggestion for warding off gophers from this article:
Use a repellent. Not as effective as a gopher trap, but worth a shot! In a glass jar mix 1/2 cup of Castor oil, 1 teaspoon of Tabasco sauce and a few drops of peppermint oil with about a cup of water. Shake well to create an emulsion. Dip cotton balls into the mixture and stick the balls into active gopher holes near plants that you want to protect. You can also put the mixture in a spray bottle and mist away.
Another option is dog poop. Use gloves! Also, since most animals are deterred by human scent, we could try the good old technique of dumping diluted human urine around problem areas.
There are poisons available, but be conscious to choose a poison that will not kill an animal that happens to eat the gopher. Safer poisons use a bait laced with anticoagulants (causes gopher to bleed internally).