Behavioural Determination of Visual Function in the Koala (Phascolarctos cinereus)

Abstract

A behavioural estimate of the koala's dependence on vision was made using fabric hoods to degrade the vision of ten male koalas. Koalas were placed on the ground in a square enclosure, with a centrally placed 'tree'. With unobstructed vision, the koalas quickly travelled across the ground to the tree and climbed it. However, with severly reduced vision, the koalas tended to raise their forelegs when walking, taking high, reaching steps. The koala appears to require a certain minimum level of vision before climbing trees. Ocular chlamydial infection, which can cause a significant visual loss, may result in similar changes in behaviour and thus contribute to mortality.