A demonstration of navigation by small rodents using an orientation cage

Abstract

The ability to ‘home’ after displacement has been demonstrated for several species of small mammals¹. Whether such homing is accomplished by random scatter², familiarity with a large area^3,4 or some kind of navigation mechanism⁵ is still unknown. The ability to navigate (to determine the direction that will lead the animal to the required destination⁷) has been shown, for example, by releasing displaced rodents on snow and analysing their tracks⁶ and by analysing for homeward bias the directions from the release point of traps in which displaced individuals were subsequently recaptured¹. Such techniques are limited in application. Moreover, the latter technique is susceptible to differential avoidance of traps by animals travelling in different directions³. It is potentially more useful to retain displaced individuals in an orientation cage and to examine their movements within the cage for evidence of orientation in the homeward direction. However, previous attempts using various types of orientation cages have yielded only negative results^8–10, except, surprisingly, when the displaced animals could not see their natural surroundings. We present the first positive evidence that small rodents will navigate while retained in an orientation cage, even when able to see their surroundings. Indeed, we show that these visual cues are important in navigation and suggest why orientation cages have previously led to negative results.