Semantics

back of the head
Я смотрел на его круглый затылок и старался не отставать. I watched the round back of his head and tried to keep up.
back of the neck
Он потёр свой красный от смущения затылок, но ничего не сказал. He rubbed the back of his neck, which had turned red from embarrassment, but he said nothing.
nape
Волосы у неё были собраны на затылке в тугой узел, а на висках завиты в мелкие кудряшки. Her hair was gathered into a tight knot at the nape of her neck, and curled in small ringlets on her temples.
This entry is concerned with the word затылок, denoting the back of the head and neck in humans. The corresponding term for animals is загривок.