Cake is a female guinea pig, around 4 1/2 years old.  After losing her friend Coffee we tried many other females to try and pair her, but Cake seems to get increasingly upset with each attempt and now will attack and bite potential bondmates. We have relunctantly dubbed her a "single pig" now.
  When piggies are kept single it is important to give them human attention and keep them in a "high traffic" area of the home so they don't get bored and lonely.