Autonomous robot navigation involves many challenges and difficulties which are augmented when multiple robots operate together. Sophisticated computational techniques are required to cope with autonomous navigation in collective robotics, being the biologically-inspired approaches the most frequently adopted. Stigmergy, i.e. the ants communication by means of pheromones, is the main biological metaphor used in this work to perform multi-robot communication. The robots will be able to mark regions of the environment with artificial pheromones, according to past experiences, assisting one another in a cooperative and indirect way to accomplish the navigation objectives. Each robot is controlled by an autonomous navigation system (ANS) based on learning classifier system, which evolves during navigation from no a priori knowledge. Besides learning to avoid obstacles and capture targets, the systems must also learn how and where to lay artificial pheromones. Some experiments and simulations are performed intending to particularly investigate the ANS from three main perspectives: capability of learning to achieve the navigation objectives in collective scenarios, adaptability in face of environmental changes and ability to obtain optimized navigation behaviors by means of stigmergy.