Not just going with the flow: foraging ants attend to polarised light even while on the pheromone trail

Pheromone cue triggers switch between vectors in the desert harvest ant, Veromessor pergandei

“…Column head foragers in all conditions appeared to rely heavily on their path integrator, orienting in the direction expected if following a vector to the nest entrance and showed no evidence of being directed to the column head. Zero vector foragers showed no evidence of using terrestrial cues or other local cues to return to the column head or nest, instead orienting consistent with backtracking behaviour (Wystrach et al 2013;Freas et al 2019c).…”

“…V. pergandei foragers also actively attend to both the sun's position and the overhead polarisation pattern while returning in the column (Freas et al 2019b). Finally, backtracking, a behaviour largely dependent on foragers running off their remaining vector (Wystrach et al 2013), is exhibited in this species only when foragers have completed over 75% of the column distance, suggesting the maintenance of a distance estimate in the column (Freas et al 2019c;Plowes et al 2019). Given these findings, fan and column foragers likely accumulate two distinct vectors during their foraging trip, a column-vector and a fan-vector.…”

“…As recent work has already concluded that foragers do not orient to the nest entrance using terrestrial cues (Freas et al 2019c), our first tests were conducted to determine whether foragers use terrestrial cues to orient to the column head. Local displacement testing was conducted at Nest 1 and Nest 4 around the column head (column length, 7.2 m at Nest 1 and 15.5 m at Nest 4).…”

“…Furthermore, the presence of a column-vector is supported by recent findings showing that foragers both attend to celestial cues and accumulate distance estimates while on the pheromone-based column. Foragers collected from the column head orient in the nest compass direction when displaced distantly (Plowes et al 2019), however this directed behaviour ceases when the sun's position is mirrored and headings become random (Freas et al 2019c). V. pergandei foragers also actively attend to both the sun's position and the overhead polarisation pattern while returning in the column (Freas et al 2019b).…”

Active Inferants: An Active Inference Framework for Ant Colony Behavior

“…In our simulation, after discovering the food, inbound foragers begin a random walk that is biased toward higher concentrations of trail pheromone and also biased toward the direction of the nest entrance. The biological plausibility of this inbound turn is well-supported by a variety of mechanisms used in ants to navigate home from foraging trips, including the path integration of steps (Heinze et al, 2018 ), location of sun and moon in the sky (Wehner and Müller, 2006 ; Freas et al, 2017 , 2019a ), magnetoreception (Freas et al, 2019b ), recognition of remembered visual scenes (Baddeley et al, 2012 ; Zeil et al, 2014 ), interactions with nestmates on the trail, non-pheromonal olfactory cues (Steck, 2012 ), the geometry of the trail network (Collett and Waxman, 2005 ; Czaczkes et al, 2015b ), and so on. Because successful foragers deposit trail pheromone on their inbound trip, they act to reinforce extant pheromone trails.…”