Spatial orientation in the arboreal crepuscular ant: Odontomachus hastatus (Formicidae: Ponerinae)

Author(s)

Pedro Augusto da Pos Rodrigues

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2009-07-20

Examining board members

Paulo Sergio Moreira Carvalho de Oliveira; Daniela Rodrigues; Karina Lucas Silva Brandão

• Advisor: Paulo Sergio Moreira Carvalho de Oliveira

Abstract

In the 'restinga' sandy plain forest of Ilha do Cardoso (SP), foragers of the crepuscular/nocturnal arboreal ant Odontomacus hastatus may hunt > 8 m away from their nests. Foraging takes place mainly in the canopy amongst the intricate net of branches and bifurcations, where ant foragers must be able to learn the way back to the nest. The canopy environment together with the nocturnal habit makes this species an interesting model for research on spatial orientation. In order to investigate orientation mechanisms employed by O. hastatus, we performed controlled laboratory experiments using a circular arena where chemical and visual cues could be manipulated. We tested the influence of: (i) an artificial canopy pattern; (ii) horizontal visual cues; (iii) a tridimensional cue (cylinder); (iv) chemical cues on the ground surface. Our results demonstrate that O. hastatus is guided mainly by visual cues (canopy and horizontal cues), which is in accordance with other diurnal arboreal ants. Nocturnal luminosity (moon/stars) is apparently sufficient to produce contrasting silhouettes from the canopy and surrounding vegetation, which may be important as orientation references. On the other hand, chemical substances provided no cues to returning foragers. Contrary to the plain floor of the circular arena, it is possible that chemical cues are important for marking bifurcated arboreal routes of O. hastatus. The use of chemical cues by ants is generally considered (AU)