The 25-year-old actress recently visited Paris with her boyfriend Ryan Phillippe, where she picked up the unusual item.
She told UK newspaper, the Daily Express: 'I bought a dead horse. I love good taxidermy – it's like art. A lot of people think it's weird, but I don't know why.'
The star also revealed that the black dress she wore for the London premiere of her new film was made by a friend of her Mamma Mia! co-star Colin Firth.
She said: 'I'm wearing a very eco-friendly dress. Livia Firth, Colin's wife, works with [designer] Karen Caldwell, who has a great line of dresses.'