Static visual predator recognition in jumping spiders

1. Visually detecting, recognizing and responding appropriately to predators increases survival. Failure to detect a predator or long decision time carries high and potentially fatal costs. Consequently, many animals show general anti-predatory responses towards threatening stimuli, for example, looming objects. However, in the context of lurking or stalking predators, visual recognition is based on static visual cues, making this task computationally demanding. 2. Jumping spiders (Salticidae) have superb vision and are excellent predators but they can equally fall prey to other jumping spiders. In a hierarchical decision-making setup, we tested whether the common zebra jumping spider Salticus scenicus can visually recognize stationary predators. We measured the spiders' behavioural responses towards predator (naturally co-occurring, non-co-occurring and artificial) and non-predator objects as well as towards objects with modified features. 3. Our experiments show that salticids demonstrate a robust, fast and repeatable 'freeze and retreat' behaviour when presented with stationary predators, but not similarly sized non-predator objects. Anti-predator responses were triggered by co-occurring and non-co-occurring salticid predators, as well as by 3D-printed salticid models (based on micro-CT scans), suggesting a generalized predator detection/classification. Using modified 3D-printed models, we found evidence that eyes act as an important cue. However, eyes alone did not explain the responses, suggesting that underlying processes rely on multiple rather than single features. 4. To address the role of learning and memory, we tested newly emerged spiderlings and found the same behavioural responses towards predator objects suggesting an innate response. The ability of jumping spiders to innately recognize a non-moving threat is surprising in terms of underlying cognitive processes and the evolution thereof. 5. Escaping from a predator before an attack has been launched likely carries sufficient selective benefits. From a cognitive perspective, the overlap of static visual characteristics between salticid predators, prey and conspecifics invites further questions considering the mechanisms of such nuanced visual discrimination and categorization in animals with complex vision but relatively small nervous systems.