A domesticated cow has surprised Polish naturalists by spending the winter living with a herd of wild bison in the primeval Bialowieza Forest.
The cow "chose freedom" by running away from a farm late last autumn, and has been seen lingering on the fringes of a herd of some 50 bison in the forest on the Belarusian border, Poland's TVN24 news portal reports.
Ornithologist Adam Zbyryt was the first to spot the cow. He made the news in November when he told TVN24: "it's not unusual to see bison near the Bialowieza Forest, but one animal caught my eye. It was a completely different light-brown shade from the rest of the herd. Bison are chestnut or dark brown".
He dropped his initial idea that this was a mutation when he trained his binoculars on the creature, and saw that it was Limousin cow - a French breed popular in Poland. The young animal appeared healthy, and unthreatened by the larger animals. Naturalists assumed it would wander back to its pasture once winter set in.
Then biologist Rafal Kowalczyk spotted the cow again this week, still apparently healthy, and keeping pace with the herd.
Dr Kowalczyk told TVN24 that this is the first time he has seen a cow join a bison herd. "She is not very integrated with the group, as bison act like one organism and she stands out." He added that the herd had probably saved her from the wolves that prowl the edges of the Bialowieza Forest through the winter.
Although the cow may be out of danger, Dr Kowalczyk warns she could pose a threat to the bison themselves.
The unusual friendship could lead to mating, which would contaminate the vulnerable population of about 600 Bialowieza bison with hybrids. "Another danger is that hybrid calves are large, and the cow could die giving birth," the biologist told TVN24.
The interloper is still too young to breed, but it looks like her winter adventure must end in recapture before spring comes.
Reporting by Martin Morgan
Use #NewsfromElsewhere to stay up-to-date with our reports via Twitter .