Ecology of fear: predator avoidance reduces seed dispersal in an ant

Abstract

The ecology of fear refers to the non-fatal cost that predators and parasites impose on prey populations. These non-consumptive effects (NCEs) can influence animal–plant interactions, but evidence thereof comes mainly from vertebrate systems with less focus on invertebrates. Here, I investigated whether the foraging behaviour of the ant Ectatomma ruidum was influenced by its primary predator, the forest toad Rhinella alata. In field tests, the probability of seed removal by the ants was 25% for seeds placed with the forest toad compared to 32% for control seeds, suggesting that toads reduce ant foraging rates. A further experiment revealed that ants which had previously encountered the predator and its faeces were more likely (59%) than inexperienced ants (50%) to avoid the exit with the predator faeces. This outcome suggests that ants are capable of learning cues associated with predation risk, possibly leading to NCEs. This indicates that predators can exert NCEs on invertebrate prey with potential cascading effects on seed dispersal, extending results previously seen only in vertebrate seed dispersal systems.

Keywords

• Ectatomma ruidum
• fear
• learning
• Rhinella alata
• myrmecochory
• three-dimensional-printed model