The choreography of learning walks in the Australian jack jumper antMyrmecia croslandi

Abstract

We provide a detailed analysis of the learning walks performed by ants at the nest during which they acquire visual information on its location Most learning walks of 12 individually marked naïve ants took place in the morning with a narrow time window separating the first two learning walks, which most often occurred on the same day. Naïve ants performed between two and seven walks over up to four consecutive days before heading out to forage. On subsequent walks, naïve ants tend to explore the area around the nest in new compass directions. During learning walks, ants move along arcs around the nest while performing oscillating scanning movements. In a regular temporal sequence, the ants' gaze oscillates between the nest direction and the direction pointing away from the nest. Ants thus experience a sequence of views roughly across the nest and away from the nest from systematically spaced vantage points around the nest. Further, we show that ants leaving the nest for a foraging trip often walk in an arc around the nest on the opposite side to the intended foraging direction, performing a scanning routine indistinguishable from that of a learning walk. These partial learning walks are triggered by disturbance around the nest and may help returning ants with reorienting when overshooting the nest, which they frequently do. We discuss what is known about learning walks in different ant species and their adaptive significance for acquiring robust navigational memories.

Opponent processes in visual memories: a model of attraction and repulsion in navigating insects’ mushroom bodies

“…We show here that the need for scanning can vanish entirely when assuming the co-existence of a second memory pathway, based on views learnt this time while facing in the anti-goal direction. This idea is corroborated by the recent observation that Myrmecia ants during their learning walks display oscillatory alternations between nest-facing and anti-nest-facing phases (48). The key is that the familiarity signal outputted by the anti-goal memory pathway must be subtracted from the signal of the goal-oriented memory pathway (or the other way around).…”

“…Furthermore, the position of nest and anti-nest oriented memories can be chosen quite arbitrarily (Figure 4A). Even though Myrmecia crosslandi ants appear to alternate regularly between nest and anti-nest facing directions (48), other species may not (61,81), and indeed according to our model, it is not needed. Also, as observed in ants, learning walks spanning larger areas provide larger catchment areas (82).…”

“…Homing is robust even to very large random deviations in memorised views orientation (e.g., ±90° around the goal and anti-goal directions) (Figure 4B). This may explain why ants displaying learning walks may not necessarily align their body precisely towards and away from the nest (12,48,61,81). Finally, most of our simulations were achieved with a typical ant resolution of 5°/pixel (53), but resolution does not need to be precisely tuned either.…”

“…These models are further supported by the well-choreographed ‘learning walks’ displayed by ants – as well as the equivalent ‘learning flights’ displayed by bees and wasps (41–45) – around their nest (or a food source). During learning walks, ants appear to systematically pause while facing towards the nest (or a food source), presumably to memorise ‘correctly aligned’ views from multiple locations around the goal (12,14,46–48). Given such a visual memory bank, models show that the exact same principle used for route following is able to produce a search centred on the goal location (24,27).…”

How do backward walking ants (Cataglyphis velox) cope with navigational uncertainty?

“…This seems counter-intuitive, 533 yet it can be explained in the light of the 'repulsive view' hypothesis. During learning walks around the nest, ants appear to store indeed both nest and anti-nest oriented 535 views (Jayatilaka, Murray, Narendra, & Zeil, 2018). Even if these nest views may be 536 all extremely familiar, the integration of attractive (nest-oriented) and repulsive (anti-537 nest oriented) views would result in a low overall directional drive, which would thus 538 lead to high peek rates (and a high probability for abandoning the crumb) but 539 nonetheless guide the ants toward the nest.…”