Effect of large visual changes on the navigation of the nocturnal bull ant, Myrmecia midas.

Nocturnal insects have remarkable visual capacities in dim light. They can navigate using both the surrounding panorama and celestial cues. Individual foraging ants are efficient navigators, able to accurately reach a variety of goal locations. During navigation, foragers compare the current panoramic view to previously learnt views. In this natural experiment, we observed the effects of large panorama changes, the addition of a fence and the removal of several trees near the nest site, on the navigation of the nocturnal bull ant Myrmecia midas. We examined how the ants' navigational efficiency and behaviour changed in response to changes in ~ 30% of the surrounding skyline, following them over multiple nights. Foragers were displaced locally off-route where we collected initial orientations and homing paths both before and after large panorama changes. We found that immediately after these changes, foragers were unable to initially orient correctly to the nest direction and foragers' return paths were less straight, suggesting increased navigational uncertainty. Continued testing showed rapid recovery in both initial orientation and path straightness.