I was able to find a bit of history online about the track. It was closed in 2008 after being in operation for 32 years. When the track shut down, the greyhounds were given away to the public on a first come, first serve basis. No home checks were done and no adoption records were kept. After a few months, people started to notice greyhounds being abused or neglected around the island. People were trying to use them as guard dogs. Some people from the States that were on Guam got involved and some of the greyhounds were rescued and sent to California for adoption.
I went back today to take some pictures of the abandoned track.