Tarangire National Park, Tanzania 2010

This is a Dik-dik, a small antelope which is common in East Africa.  They are so named for the alarm calls of the females.  In addition to the alarm call, males and females can make a shrill whistling sound.  Dik-diks mate for life, and where you see one you will invariably find the other one nearby.  In fact, if one of a pair falls to a predator, the other will likely die of loneliness.