Here is a common problem this spring as superintendents remove covers from greens and tees. It is vole damage caused by feeding on bentgrass and other species by these small rodents. It can also take place under snow cover, although we had little of that in the Midwest this winter.
Picture courtesy of Tim Christians at Makray Memorial Golf Club, Barrington, Ill.
Voles are mouse-like rodents with a shorter body, shorter hairy tails, and smaller ears. They are sometimes referred to as field mice in this region. According to Wikipedia, there are approximately 155 species of voles that vary from quite small up to nine inches in length. My guess is that they all like grass. Voles have underground nests and do not hibernate, which means that they have a lot of time in the winter to feed. There are traps, baits and repellents available, but success with these is usually limited.
Fortunately, with a little topdressing and fertilizer, the problem is easily repaired in the spring However, they can certainly be annoying when you first pull the covers off.
Picture courtesy of Tim Christians Makray Memorial Golf Club, Barrington, Ill.