The tallest mammals on earth are the one and only giraffe. It is obvious from one glance at them why that previous statement is true. Be careful not to get a kink in your neck from looking up at these animals to long. When your feet feel tired from standing all day from a hard day's work, imagine spending most of your entire life standing up, either to sleep, eat, or give birth. That is the life of a giraffe. Giraffes are one of the most popular zoo animals.