randomly assign 1,2, or 3 to unique character string

I have a character vector and I want to randomly assign numerical categories 1, 2, or 3 to each character string in the character vector. How can I do this in R

Input

Species
Species1 
Species2
Species3
Species4
Species5

Example output

Species   Category
Species1  2
Species2  1 
Species3  1
Species4  3
Species5  3