Harri, M., Mononen, J. and Sepponen, J. 1999. Preferences of farmed silver foxes (Vulpes vulpes) for four different floor types. Can. J. Anim. Sci. 79: 1-5. Farmed silver foxes were allowed to choose between four standard farm cages, each of which was equipped with a different floor material: plastic-coated wire mesh (WM); dry wood (DW); dry sand (DS); and wet wood (WW) or icy sand (IS). Six males and six females were placed in the test environment singly in winter; and the same individuals, again in spring. The use of the different floors was videorecorded and analysed from the tapes for active periods and resting period on 5 or 6 d. Resting consisted of 14-20 separate bouts d -1 , occupying 58-62% of the total 24 h. In winter, the active periods of the animal's day were spent as follows: DW (34%) = DS (33%) > IS (17%) = WM (15%). The resting periods were spent as follows: DW (59%) > WM (26%) = DS (15%) > IS (1%). In spring, the order of active time was DS (36%) > DW (25%) = WW (24%) > WM (15%) and of resting time was DW (51%) > WM (19%) = WW (16%) = DS (15%). Different individuals preferred different floors, leading to large variance in the group means. This high variation may suggest a low level of priority in general but a high level of priority within individuals. Although solid floors were highly preferred when dry, they were least preferred when wet or icy. Preference tests have been used to measure animals' choices for different aspects of housing design, such as nest sites, floor type and material, and several physical factors of the environment, such as air quality, temperature, draft, noise and vibration (Nicol 1997).Animals' priorities are affected by several aspects of their internal state and external environment, including the presence of eliciting stimuli, the number of behavioural opportunities available, the size of the animals' time and energy budgets, a lack of transitivity or lack of common currency of the preferences, and the consequence or pleasure of behaviour directed at the stimuli (Lawrence and Illius 1997;Mason et al. 1997;Nicol 1997). Therefore, understanding the underlying motivational mechanisms of the choices is of utmost importance.For testing the decision-making process of the animal, two principally different experimental environments have been used: either an animal has the possibility of visiting separate resource chambers from a "home cage" or a central chamber, where it can spend considerable time as well