Physical and optical shelter characteristics influence rat's preferences in a multiple Y-maze

Rat's preference for covered or uncovered sections of a multiple Y-maze, measured as time spent under cover, was investigated. Surface area of covered and uncovered sections was the same. There were no light-intensity differences between uncovered and covered sections. Coverings were of two types: transparent or sanded plexiglas, affording respectively only physical or physical and optical protection. Both types of covering were placed either over discontinuous sections of the maze or continuously over one entire half of it. Male adult Wistar rats were employed. Rats exhibited maximal preference for the continuous sanded covering. They also exhibited a very similar significant preference for the continuous transparent covering and the discontinuous sanded one. Equal permanence time was measured in uncovered sections and under discontinuous transparent coverings. The results show that rats can recognize and choose shelter even when there is no light diminution under it. In fact they can very well discriminate between the several types of shelter, as shown by their significant longer permanence under the most protective and most continuous one. Finally, results are taken as basis for discussing whether the accepted "dark preference" of rats may be due solely to photophobia or also to the fact that normally darkness indicates a shelter.