Mirror usage has been taken to indicate some degree of awareness in animals. Can pigs, Sus scrofa, obtain information from a mirror? When put in a pen with a mirror in it, young pigs made movements while apparently looking at their image. After 5 h spent with a mirror, the pigs were shown a familiar food bowl, visible in the mirror but hidden behind a solid barrier. Seven out of eight pigs found the food bowl in a mean of 23 s by going away from the mirror and around the barrier. Naïve pigs shown the same looked behind the mirror. The pigs were not locating the food bowl by odour, did not have a preference for the area where the food bowl was and did not go to that area when the food bowl was visible elsewhere. To use information from a mirror and find a food bowl, each pig must have observed features of its surroundings, remembered these and its own actions, deduced relationships among observed and remembered features and acted accordingly. This ability indicates assessment awareness in pigs. The results may have some effects on the design of housing conditions for pigs and may lead to better pig welfare.
Centre for Animal Welfare and Anthrozoology, Department of Veterinary Medicine, University of Cambridge, U.K. Received 15 January 2009; revised 18 February 2009; accepted 26 July 2009. MS. number: 09-00034R. Available online 25 September 2009.