"It`s the best picture I`ve ever taken in my life," Don told BBC News.
"It`s the symmetry of the heads, the bodies and the tails - even the expression on the faces."
The two animals` ranges overlap at Wapusk, which hugs the shore of Hudson Bay in Manitoba.
And if the larger red catches sight of the Arctic resident, it will try to predate the northern species.
Wildlife guides in the park had spoken of seeing the conflict, but this is thought to be one of the first cases where it has been documented on camera.
Kathy Moran, who sat on the judging panel, said the horror of the scene was surprisingly understated.
"It doesn`t come across as gory at all. If fact, when you first look at the picture - it`s almost as if the red fox is taking off his winter coat."
Kathy, who is National Geographic magazine`s senior editor for natural history projects, also described it as an image with a powerful message about climate change.
"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.
Don 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.
"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."
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