USPENIVKA, Ukraine — Aleksandr Podlesnyi saw the lunge before he recognized the shape as a wolf.

His first thought was, Where did you come from?

As the wolf clamped onto his left arm, his second thought was, I will kill him or he will kill me.

Mr. Podlesnyi, 41, had emerged from his outhouse early on Dec. 9, intending to feed his chickens and ducks. Instead, he found himself becoming an extreme example of the unintended consequences of a war that has simmered for four years in eastern Ukraine between Ukrainian forces and Russian-backed separatists.

Hunting is prohibited in areas extending as far as 40 miles from the front line to minimize confusion about who is shooting at what target. As a result, prey like pheasants and hares are proliferating. And predators like foxes and wolves are appearing in greater numbers and coming into closer contact with humans, pets and barnyard animals in rural areas.