Landmarks and ant search strategies after interrupted tandem runs

Abstract

During a tandem run, a single leading ant recruits a single follower to an important resource such as a new nest. To examine this process, we used a motorized gantry, which has not previously been used in ant studies, to track tandem running ants accurately in a large arena and we compared their performance in the presence of different types of landmark. We interrupted tandem runs by taking away the leader and moved a large distant landmark behind the new nest just at the time of this separation. Our aim was to determine what information followers might have obtained from the incomplete tandem run they had followed, and how they behaved after the tandem run had been interrupted. Our results show that former followers search by using composite random strategies with elements of sub-diffusive and diffusive movements. Furthermore, when we provided more landmarks former followers searched for longer. However, when all landmarks were removed completely from the arena, the ants' search duration lasted up to four times longer. Hence, their search strategy changes in the presence or absence of landmarks. Even after extensive search of this kind, former followers headed back to their old nest but did not return along the path of the tandem run they had followed. The combination of the position to which the large distant landmark behind the new nest was moved and the presence or absence of additional landmarks influenced the orientation of the former followers' paths back to the old nest. We also found that these ants exhibit behavioural lateralization in which they possibly use their right eye more than their left eye to recognize landmarks for navigation. Our results suggest that former follower ants learn landmarks during tandem running and use this information to make strategic decisions.

Miniaturisation decreases visual navigational competence in ants

“…2A, last row). While it is tempting to discuss this in the context of laterality, for which there is evidence in ants and bees at both the population and individual level (Basari et al, 2014;Frasnelli et al, 2012;Hunt et al, 2014;Ong et al, 2017), we think that is not the case here. We think the bias may be Table S1).…”

How collective comparisons emerge without individual comparisons of the options

“…Would these ants in their natural habitat even have the opportunity to visit more than one nest, and therefore be in a position to make comparisons? There have been no field studies that address this directly, however, inter-nest distances in the wild can be low (frequently less than 30 cm; E. J. H. Robinson and N. R. Franks 1992–2013, personal observation) compared with the much greater distances over which laboratory colonies will readily emigrate, with scouts visiting pairs of nests that are separated by as much as 1.2 m [20,37]. This gives an indication that we would expect some ants to have the opportunity to encounter multiple sites in the wild, however, across the scouting population, the information obtained may be very variable.…”

Ants show a leftward turning bias when exploring unknown nest sites

“…Population-level asymmetry has also been observed in the red wood ant Formica aquilonia , where ants receiving food via trophallaxis use the right antenna to stimulate their donor ant significantly more than the left antenna [ 8 ]. Recent research has found that workers of the house-hunting ant Temnothorax albipennis seem to rely more on their right eye to recognize landmarks for navigation [ 9 ]. This is similar to the finding that bees ( Apis mellifera ) predominantly use their right eye for learning and/or detecting objects [ 10 ].…”