 Of the subspecies , the black @-@ faced impala is significantly larger and darker than the common impala ; a recessive gene is responsible for the black colouration . Distinctive of the black @-@ faced impala is a dark stripe , on either side of the nose , that runs upward to the eyes and thins as it reaches the forehead . Other differences include the larger black tip on the ear , and a bushier and nearly 30 % longer tail in the black @-@ faced impala . 
