Representation of different exact numbers of prey by a spider-eating predator

Abstract

Our objective was to use expectancy-violation methods for determining whether Portia africana , a salticid spider that specializes in eating other spiders, is proficient at representing exact numbers of prey. In our experiments, we relied on this predator's known capacity to gain access to prey by following pre-planned detours. After Portia first viewed a scene consisting of a particular number of prey items, it could then take a detour during which the scene went out of view. Upon reaching a tower at the end of the detour, Portia could again view a scene, but now the number of prey items might be different. We found that, compared with control trials in which the number was the same as before, Portia 's behaviour was significantly different in most instances when we made the following changes in number: 1 versus 2, 1 versus 3, 1 versus 4, 2 versus 3, 2 versus 4 or 2 versus 6. These effects were independent of whether the larger number was seen first or second. No significant effects were evident when the number of prey changed between 3 versus 4 or 3 versus 6. When we changed prey size and arrangement while keeping prey number constant, no significant effects were detected. Our findings suggest that Portia represents 1 and 2 as discrete number categories, but categorizes 3 or more as a single category that we call ‘many’.

Spontaneous quantity discrimination in crickets

“…However, control experiments suggested that this ant species discriminate among nest sites by relying on the summation of light levels within nesting entrances rather than counting the exact number of available cavity entrances. Thus, the results found by Franks et al () and other studies (Cross & Jackson, ; Nelson & Jackson, ) have highlighted the need for carefully considering alternative explanations before concluding that animals attend to strictly numerical information.…”

“…Ladybirds, ants, beetles, and spiders assess the number of potential competitors when searching for food sources or selecting potential mates to avoid conflicts (Carazo, Fernández‐Perea, & Font, ; Hemptinne, Dixon, & Coffin, ; Nelson & Jackson, ; Tanner, ). However, studies on invertebrates have not gone especially far toward disentangling which attributes are exploited in quantity discrimination (but see Cross & Jackson, ; Nelson & Jackson, ; Yang & Chiao, ). The core distinction is between analogue variables (e.g., continuous features of stimuli as the overall surface encompassed by stimuli) and discrete variables (e.g., individuated single items within groups corresponding to exact, discrete numbers).…”

Visual Discrimination Learning in the Jumping Spider Phidippus regius

“…Arthropods appear able to perform a variety of complex tasks, ranging from spatial navigation (Menzel et al, 2005;Wehner, 2003) to object perception (van Hateren, Srinivasan, & Wait, 1990), learning (Hammer & Menzel, 1995), numerical competences (Cross & Jackson, 2017;Dacke & Srinivasan, 2008;Nelson & Jackson, 2012) and even more complex skills, such as self-recognition (Cammaerts & Cammaerts, 2015) and the cultural spreading of learned abilities (Alem et al, 2016). Among arthropods, a family of spiders has caught the interest of scientists: Salticidae.…”

Convergent minds: the evolution of cognitive complexity in nature

“…Cross & Jackson [34] detail an experimental test for numerical cognition in the Portia jumping spider, from which they conclude that these arachnids appear to represent the quantities '1' and '2' as discrete numerical categories; moreover, they likely discriminate among these through a method other than, for example, relying on discriminating between the timing of different sets of events. Their experimental set-up relies on the spiders' well known ability to select the most effective path (which is not necessarily the most direct one) in pursuit of prey, which is itself suggestive of the possession of a cognitive map, or an internal representation of the relationship among objects in an environment.…”