Most of the buck in Africa have large ears, and can hear very well. This a female Impala, and she has been startled by something. They will stand dead still, and listen carefully. If there is a predator, they will bark to warn others, but will also scamper away. Taken in the Kruger National park, a few weeks ago.
Canon 50D
100-400 L IS USM @ 400mm
1/800
F/8
ISO 400