Higher latitudes are warming fast, allowing animals that would not normally come into contact to cross each other's ranges.
"As it gets warmer in the Arctic and sub-Arctic and the red fox can move further north into the territory occupied by the Arctic fox, you are going to get increasingly these kinds of tensions," she said.
Mr Gutoski was named as Wildlife Photographer of the Year (WPY) on Tuesday, at a ceremony at London's Natural History Museum. The NHM owns and organises the competition.
The judges sorted through 42,000 entries submitted from almost 100 countries.
"A Tale of Two Foxes", as the winning image is known, will now feature in an exhibition that will open at the museum on Friday before, at a later date, going on tour.
WPY, which has been running now for over 50 years, is divided into 18 categories, each with its own best in class.
The second big overall prize is the Junior Wildlife Photographer of the Year.
This has gone to 14-year-old Ondrej Pelánek from the Czech Republic for his image, Fighting Ruffs.
The birds are waders and are known for their "rough" behaviour during courting. Ondrej pictured them on Varanger Peninsula in the far north of Norway.
"This is a scene that many adult photographers have tried to capture, and Ondrej has really got it," said Kathy Moran.
Published: 2015-10-14 16:27:21
"It's graphic; the behaviour is all there; every element you would want in a photograph has come together in the moment. And to know that it was taken by one of our young photographers gives it an extra dimension."