Tandem communication improves ant foraging success in a highly competitive tropical habitat

S M Glaser,C Grüter,A Koch,R M Feitosa,N Goß,F S Do Nascimento

doi:10.1007/s00040-021-00810-y

Abstract

Tropical ants experience intense intra- and interspecific competition for food sources, which influences their activity pattern and foraging strategies. Even though different ant species can coexist through spatial and temporal niche partitioning, direct competition for food cannot be avoided. Recruitment communication is assumed to help colonies to monopolize and exploit food sources successfully, but this has rarely been tested under field conditions. We studied if recruitment communication helps colonies of the Neotropical ant Pachycondyla harpax to be more successful in a highly competitive tropical environment. Additionally, we explored if temporal and spatial niche differentiation helps focal colonies to avoid competition. Pachycondyla harpax competed with dozens of ant species for food. Mass-recruiting competitors were often successful in displacing P. harpax from food baits. However, when foragers of P. harpax were able to recruit nestmates they had a 4-times higher probability to keep access to the food baits. Colonies were unlikely to be displaced during our observations after a few ants arrived at the food source. Competition was more intense after sunset, but a disproportionate increase in activity after sunset allowed focal colonies to exploit food sources more successfully after sunset. Our results support the hypothesis that recruitment communication helps colonies to monopolize food sources by helping them to establish a critical mass of nestmates at large resources. This indicates that even species with a small colony size and a slow recruitment method, such as tandem running, benefit from recruitment communication in a competitive environment.

Highlights

The tropics are home to thousands of ant species, some forming colonies containing millions of ants
The results show that significantly more ants reached the food source when recruitment took place (Fig. 2a) (GLMER: z = 5.942, p < 0.001)
We found that the probability of having access increased significantly with an increasing number of foragers at the food bait (Fig. 2c) (GLMER: z = 2.723, p = 0.006): P. harpax colonies had a 100% access chance when at least three ants were at the food source

Summary

Introduction

The tropics are home to thousands of ant species, some forming colonies containing millions of ants. Their biomass exceeds the biomass of all wild mammals combined (Bar-On et al 2018) as they fulfill vital ecological roles as predators, herbivores or soil architects (Hölldobler and Wilson 1990; Davidson et al 2003). Often species occupy particular dietary niches, e.g. by exploiting different food types (sugars, carrion, excrements, seeds, and live prey) or food sizes (Torres 1984; Houadria et al 2015). Species can show temporal activity patterns that allow them to avoid competitors (Torres 1984; Stuble et al 2013; Houadria et al 2016; Rosumek 2017). Nocturnal species like some Myrmecia or Polyrhachis ants have adapted to low light levels by developing large eyes and efficient navigational strategies

Results

Discussion

Conclusion