An elephant is seen at the Maasai Mara National Reserve, Kenya, July 13, 2016. The Maasai Mara National Reserve, popularly known as Africa's Greatest Wildlife Reserve, is a great tourist attraction center as it offers visitors an opportunity to observe the Africa's "big five": lion, cheetah, elephant, buffalo and rhino. (Xinhua/Meng Tao)

Crocodiles are seen on the bank of Mara River at the Maasai Mara National Reserve, Kenya, July 14, 2016. The Maasai Mara National Reserve, popularly known as Africa's Greatest Wildlife Reserve, is a great tourist attraction center as it offers visitors an opportunity to observe the Africa's "big five": lion, cheetah, elephant, buffalo and rhino. (Xinhua/Meng Tao)

Gnus swim across the Mara River at the Maasai Mara National Reserve, Kenya, July 14, 2016. The Maasai Marra National Reserve, popularly known as Africa's Greatest Wildlife Reserve, is a great tourist attraction center as it offers visitors an opportunity to observe the Africa's "big five": lion, cheetah, elephant, buffalo and rhino. (Xinhua/Meng Tao)

Gnus swim across the Mara River at the Maasai Mara National Reserve, Kenya, July 14, 2016. The Maasai Marra National Reserve, popularly known as Africa's Greatest Wildlife Reserve, is a great tourist attraction center as it offers visitors an opportunity to observe the Africa's "big five": lion, cheetah, elephant, buffalo and rhino. (Xinhua/Meng Tao)

Gnus swim across the Mara River at the Maasai Mara National Reserve, Kenya, July 14, 2016. The Maasai Marra National Reserve, popularly known as Africa's Greatest Wildlife Reserve, is a great tourist attraction center as it offers visitors an opportunity to observe the Africa's "big five": lion, cheetah, elephant, buffalo and rhino. (Xinhua/Meng Tao)

A gnu jumps into the Mara River at the Maasai Mara National Reserve, Kenya, July 14, 2016. The Maasai Marra National Reserve, popularly known as Africa's Greatest Wildlife Reserve, is a great tourist attraction center as it offers visitors an opportunity to observe the Africa's "big five": lion, cheetah, elephant, buffalo and rhino. (Xinhua/Meng Tao)

Gnus swim across the Mara River at the Maasai Mara National Reserve, Kenya, July 14, 2016. The Maasai Marra National Reserve, popularly known as Africa's Greatest Wildlife Reserve, is a great tourist attraction center as it offers visitors an opportunity to observe the Africa's "big five": lion, cheetah, elephant, buffalo and rhino. (Xinhua/Meng Tao)

Gnus swim across the Mara River at the Maasai Mara National Reserve, Kenya, July 14, 2016. The Maasai Marra National Reserve, popularly known as Africa's Greatest Wildlife Reserve, is a great tourist attraction center as it offers visitors an opportunity to observe the Africa's "big five": lion, cheetah, elephant, buffalo and rhino. (Xinhua/Meng Tao)