Shayne Patrick Burke was on a short hike this month to photograph owls in the backcountry of Grand Teton National Park in Wyoming when he spotted a grizzly bear cub about 50 to 70 yards in front of him.

Instantly, Mr. Burke knew that the cub’s presence signaled trouble, he wrote on Instagram.

Moments later, Mr. Burke, 35, was attacked by the cub’s mother.

He turned his back, got on his stomach and locked his hands behind his neck, following advice he had read about grizzly bear attacks, he said.

During the attack, on May 19, the bear repeatedly bit Mr. Burke and picked him up and slammed him to the ground, before, he wrote, one of his screams “unfortunately, but fortunately, turned her attention to my head.”

It was a terrifying moment, but it ultimately saved his life.

The bear bit at Mr. Burke’s neck, but his hands and arms were still interlocked behind it and, crucially, he had grabbed a can of bear spray when he saw the cub.

“I never let go of the bear spray can,” he wrote. “As she bit my hands in the back of my neck she simultaneously bit the bear spray can and it exploded in her mouth.”