Having just given birth to its newborn, this bison immediately had her motherhood tested.

The tense moment was captured by ranger Joy Guffy, whose images were posted on Yellow Stone National Park’s twitter page.

The coyote kept edging closer and closer, testing the mother’s nerve. Eventually making a break for it, the opportunist hunter managed to get close enough to grab hold.

The mother’s fierce response successfully deterred the coyote – placing herself determinedly in front of her calf, she gave it little choice than to search for a meal elsewhere.

The Bison mother’s exploits went down well on Twitter.

“After giving birth, a cow bison successfully defended her newborn calf from a very determined coyote,” Yellow National Park wrote.