Nest excavators' learning walks in the Australian desert ant Melophorus bagoti

Abstract

The Australian red honey ant, Melophorus bagoti, stands out as the most thermophilic ant in Australia, engaging in all outdoor activities during the hottest periods of the day during summer months. This species of desert ants often navigates by means of path integration and learning landmark cues around the nest. In our study, we observed the outdoor activities of M. bagoti workers engaged in nest excavation, the maintenance of the nest structure, primarily by taking excess sand out of the nest. Before undertaking nest excavation, the ants conducted a single exploratory walk. Following their initial learning expedition, these ants then engaged in nest excavation activities. Consistent with previous findings on pre-foraging learning walks, after just one learning walk, the desert ants in our study demonstrated the ability to return home from locations 2 m away from the nest, although not from locations 4 m away. These findings indicate that even for activities like dumping excavated sand within a range of 5-10 cm outside the nest, these ants learn and utilize the visual landmark panorama around the nest.

Keywords: Exploratory walks; Navigation; Nest excavation; Red honey ant.

Fig. 1

Naive learning walk and nest-excavating ants’ paths. The line graphs show the naïve learning walks of excavators (A), each ant represented by a different colour, and same ants’ first (B), second (C) and third (D) round-trips during the sand-excavation. The nest is located at (0, 0)

Fig. 2

Characteristics of naive learning walks and three consecutive excavation trips of ants at the nest. (A) Convex hull area, (B) maximum displacement from the nest, and (C) duration of the walk. The boxes indicate the median and quartiles, while the whiskers show extreme values excluding outliers. Each point represents a single trajectory. LW on x axis denotes the excavator learning walk

Fig. 3

Comparison of speed, orientation angular velocity and scanning bouts of excavators during the learning walk and three consecutive excavation trips. The violin plots show the mean speed of ants across their entire trajectory (A). The half violin plots show the distribution of bootstrapped differences of mean orientation angular velocity of ants during the learning walk and consecutive excavation trips (B). Number of scanning bouts of naive ants during the learning walk and next three consecutive excavation trips (C). In all graphs, the solid dot shows the mean, while the vertical bar shows 95% confidence interval of the mean

Fig. 4

Circular histograms of initial headings of foragers during the displacement test on North 2 m (A), East 2 m (B), North 4 m (C) and East 4 m (D) tests. In the histograms, the nest direction is set at 0°. The arrows denote the length and direction of the mean vector

Fig. 5

(A to E) Panoramic views at various tested locations, all aligned towards the nest direction: at (A) the Nest, (B) 2 m North, (C) 4 m North, (D) 2 m East, and (E) 4 m East. F). The rotational image difference function for each location when compared with the nest panorama facing the direction of the nest. Table in the inset shows the minimum, median, mean and mean depth at each test location when compared with the nest panorama facing the direction of the nest

Fig. 6

Path characteristics of ants at different displacement locations: (A) sinuosity, (B) and (C) straightness. Box plots display the median (line inside the box), interquartile range (box), and extreme values excluding outliers (whiskers). Individual data points are shown as dots

Fig. 7

Comparison of speed and orientation angular velocity of ants at different displacement locations. The violin plots show the mean speed of ants across their entire trajectory at the displacement locations (A). The half-violin plots show the distribution of bootstrapped differences of mean orientation angular velocity of ants at the various displacement locations (B). In (A) and (B), the solid dot shows mean, while the vertical bar shows 95% confidence interval of the mean

Fig. 8

Characteristics of first learning walks of naive excavators and naive foraging ants at the nest. The line graphs show the first learning walks of excavators (A) and foragers (B). C) Convex hull area, D) maximum displacement from the nest, E) duration of the walk and F) Number of scans during the learning walks. The boxes indicate the median and quartiles, while the whiskers show extreme values excluding outliers. Each point represents a single trajectory. ELW denotes the excavators’ learning walk whereas NLW represents the first learning walk of foragers