Search

Although a wide range of vertebrates have been considered in research on numerical competence, little is known about the role of number-related decisions in the predatory strategies of invertebrates. Here, we investigate how numerical competence is expressed in a highly specialized predatory strategy adopted by the small juveniles of Portia africana when practicing communal predation, with the prey being another spider, Oecobius amboseli. Two or more P. africana juveniles sometimes settle by the same oecobiid nest and then share the meal after one individual captures the oecobiid. Experiments were designed to clarify how these predators use number-related cues in conjunction with non-numerical cues when deciding whether to settle at a nest. We used lures (dead spiders positioned in lifelike posture) arranged in a series of 24 different scenes defined by the type, configuration and especially number of lures. On the whole, our findings suggest that P. africana juveniles base settling decisions on the specific number of already settled conspecific juveniles at the nest and express a preference for settling when the number is one instead of zero, two or three. By varying the size of the already settled juveniles and their positions around the nest, we show that factors related to continuous variables and stimulus configuration are unlikely explanations for our findings. [ABSTRACT FROM AUTHOR]

Examines scanning and route selection abilities of the jumping spider Portia labiata. Use of three different kinds of detours leading to a lure; Spider's choice of the complete route after visually inspecting two routes; Fixation on one route.

Examines the ability of Portia fimbriata from Queensland, Australia to choose between detour paths. Number of set-ups used in study; Types of detours; Frequency of correct route selection; Relationship between time of delay and route selection; Abandonment of wrong route detour.