Concept:
In classification questions, identify the common characteristic shared by most items and locate the item that does not belong to the group.
Step 1: Analyze the animals.
Elephant, Camel, Horse, Bison and Donkey are generally domesticated animals or animals used directly by humans for transportation, agriculture, carrying loads, or other economic activities.
Step 2: Examine Bear.
Bear is primarily a wild animal and is not domesticated for routine human use.
Thus it differs from the remaining animals.
Step 3: Conclusion.
Therefore the odd one out is
\[
\boxed{\text{Bear}}.
\]