BIALOWIEZA NATIONAL PARK, Poland — The two great, glowering creatures paused from their noisy feeding, silhouetted against the pencil-thin pines on the far side of a meadow, and emitted a couple of steam-train snorts.

“I think we have gone close enough,” said Michal Krzysiak, who is part of a 23-member team overseeing this sprawling park’s European bison herd and is its only veterinarian. “We may scare them away, or they may charge.”

The two bison — among the 1,500 or so here in Bialowieza, the largest concentration of the European variety in the world — took turns lowering their heads to the thick grass and ripping at it with their rough, gray tongues.

Dr. Krzysiak, 34, watched them with avid interest, the rooftops of the small village of Teremiski rising a few hundred yards behind him. At first, he said, residents of villages in and around the park were leery of the bison and worried about the impact on their properties. Yet the animals became part of the landscape and now, he said, the villagers refer to them as “our bison.”