Irishman at the zoo

an irish man and his son go to the zoo. a sign says "feed the elephant a bun and he will tell you your age". the little boy gives the elephant a bun and it stamps it foot 6 times. "wow" says the boy thats right i am 6 years old. "you have a go dad". the irish chap gives the elephant a bun...a moment later the elephant farts and stamps its foot twice. "be jesus that's right" says the father "i am farty - two"?