Errors in geography: Despite the movie supposedly taking place in the Maine woods, foliage and landmarks clearly show the area of the forests of British Columbia, where the movie was actually filmed.
Plot holes: In the opening sequence, the dog can be seen to be hanging over 40 feet above the ground. Yet the bear (unseen) manages to pluck it down, despite clearly being too short in later scenes.
Revealing mistakes: Obvious dummy dog falling over cliff in opening sequence.
Revealing mistakes: Obvious dummy for M'Rai when he is killed and thrown by the bear.
Revealing mistakes: Clear use of wires when Hawk is thrown by bear.
Revealing mistakes: Obviously stuffed bear to represent dead monster-bear floating in the lake.
Factual errors: Generally, and especially when giving chase, bears do not run on their hind legs.
Errors in geography: Dr. Verne and his wife fly from Washington D.C. to Maine, but when they pass over a lighthouse on the coast the plane is clearly traveling south.