why does a giraffe have a blue tongue?

Question: why does a giraffe have a blue tongue?
- Keywords:
  blue,
  colour,
  giraffe,
  tongue
Asked by evex to Charlotte, Jo, Kevin, Louise, Valeria on 15 Jun 2012.
- Kevin Mahon answered on 15 Jun 2012:
  
  Because it has so few blood vessels in it, it almost appears blue-black. Some scientists believe this has evolved due to the giraffe eating so many thorny/prickly plants, to avoid the tongue constantly bleeding!

Question: why does a giraffe have a blue tongue?