Tandem running by foraging Pachycondyla striata workers in field conditions vary in response to food type, food distance, and environmental conditions

Ants show collective and individual behavioural flexibility in their response to immediate context, choosing for example between different foraging strategies. In Pachycondyla striata, workers can forage solitarily or recruit and guide nestmates to larger food sources through tandem running. Although considered more ancestral and less efficient than pheromone trail-laying, this strategy is common especially in species with small colony size. What is not known is how the decision to recruit or follow varies according to the immediate context. That is, how fine adjustments in information transfer affect immediate foraging decisions at the colony level. Here, we studied individually marked workers and evaluated their foraging decisions when food items varied in nature (protein vs carbohydrate), size, and distance from the nest at different temperatures and humidity levels. Our results show that tandem run leaders and potential followers adjust their behaviour according to a combination of external factors. While 84.2% of trips were solitary, most ants (81%) performed at least one tandem run. However, tandem runs were more frequent for nearby resources and at higher relative humidity. Interestingly, when food items were located far away, tandem runs were more successful when heading to protein sources (75%) compared to carbohydrate sources (42%). Our results suggest that the social information transfer between leaders and followers conveys more information than previously thought, and also relies on their experience and motivation.

On the Development of an Ants-Inspired Navigational Network for Autonomous Robots

Experimental research in biology has uncovered a number of different ways in which ants use environmental cues for navigational purposes. For instance, pheromone trail laying and trail following behaviours of ants have proved to be an efficient mechanism to optimise path selection in natural as well as in artificial situations. Drawing inspiration from biology, the authors present a new neural strategy for navigation. The authors propose a navigational network composed of a gating network, memory and two recurrent neural networks (RNN). The navigational network learns to follow a trail and to orientate based on landmarks, while continuously recording the location of the home position in case the trail is lost. The orientation was encoded as a continuous ring of neurons, while the distance was encoded as a chain of neurons. Finally, the computational analysis provides a more complete exploration of the properties of the proposed navigational network. This network is able to learn and select behaviours based on sensory clues. The proposed model shows that neural path integration is possible and is easy to achieve.

Trail-Laying Behaviour as a Function of Resource Quality in the AntCamponotus rufipes

Chemical trails have been shown to act as an orientation cue in some ant species. Here, I report that the trail-laying behaviour in the nectar-feeding ant,Camponotus rufipes, varies with the concentration of the sucrose solutions collected. Single workers collected solutions of different sucrose concentrations (5%, 20%, and 40% in weight) during 4 consecutive visits to the resource, and their trail-marking behaviour was recorded on soot-coated slides during their first and last visits. Results suggest that these chemical trails provide both an orientation cue between the nest and the food source, as previously suggested forCamponotusants, as well as information about food quality.

Nest Relocation and Colony Founding in the Australian Desert Ant,Melophorus bagotiLubbock (Hymenoptera: Formicidae)

Even after years of research on navigation in the Red Honey Ant,Melophorus bagoti, much of its life history remains elusive. Here, we present observations on nest relocation and the reproductive and founding stages of colonies. Nest relocation is possibly aided by trail laying behaviour, which is highly unusual for solitary foraging desert ants. Reproduction occurs in synchronised mating flights, which are probably triggered by rain. Queens may engage in multiple matings, and there is circumstantial evidence that males are chemically attracted to queens. After the mating flight, the queens found new colonies independently and singly. Excavation of these founding colonies reveals first insights into their structure.