Early this morning my driveway bell rang. When I looked out, I saw two large dark cats with stubby ears walking at a fast pace side by side. Very strange looking. No way were these domestic cats. I have two cats that go outside with me for a little while everyday. Now I am thinking I better fence them in or just keep them inside. I live in farm country with no houses or barns around--just open fields. Any idea what these creatures are? Thanks.

Did they have short tails?

Not sure about the tails. I think I would have noticed long tails but was focused on their odd faces and short ears. They were maybe 3 times as big as a large domestic cat. They traveled side by side pretty swiftly but not running. I know they were dark in color. They were just very odd and creepy looking.