It’s possible Kubrick placed the bear imagery in the film because it matches the story's theme of fathers murdering their wives and children. Adult male bears are known to kill bear cubs which are not their own and sometimes kill the cubs' mother in the process.
Left on the cutting room floor because it didn't look convincing. As a still, it's pure nightmare fuel.
Saturday Night Fever is not a polite movie. Or a feel-good buffet of sunny escapism. It's a frequently gritty slice-of-life character drama, stocked with complicated characters, illustrating some hard, uncomfortable truths.
These are the sorts of details a lot of screenwriters and producers might instinctively tone down, or omit altogether, on the assumption audiences would find them too far-fetched and 'movie-like', despite the fact they were true.