Plasticity, learning and cognition

2012

Anim Cogn

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.

Section: Introductionmentioning

confidence: 99%

The role of numerical competence in a specialized predatory strategy of an araneophagic spider

Nelson

2012

Anim Cogn

“…This, in turn, implies that trial and error signal generation is at least a rudimentary example of learning (see Staddon 1983;Jakob et al 2011), or more specifically operant conditioning (Skinner 1938). However, many questions related to learning remain.…”

Section: Discussionmentioning

confidence: 99%

Reliance on trial and error signal derivation by Portia africana, an araneophagic jumping spider from East Africa

Nelson

2011

J Ethol

All species from the jumping spider (Salticidae) genus Portia appear to be predators that specialize at preying on other spiders by invading webs and, through aggressive mimicry, gaining dynamic fine control over the resident spider's behavior. From previous research, there is evidence that P. fimbriata, P. labiata and P. schultzi derive signals by trial and error. Here, we demonstrate that P. africana is another species that uses a trial and error, or generate and test, algorithm when deriving the aggressive-mimicry signals that will be appropriate in different predator-prey encounters. We discuss the implications of these new findings and the findings from previous work in order to understand the selection factors that drive the evolution of flexibility in aggressive-mimicry strategies.

“…Webb 2012) and spiders (e.g. Jakob et al 2011) challenge the convention of assuming that there are severe constraints on the expression of cognition by small animals. For research on visual cognition, jumping spiders (Salticidae) are of particular interest because their unique, complex eyes (Land and Nilsson 2012) support highly precise identification of different prey types and other visual objects (Harland et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Solving a novel confinement problem by spartaeine salticids that are predisposed to solve problems in the context of predation

Cross

2014

Anim Cogn

Especially intricate predatory strategies are widespread in the salticid subfamily Spartaeinae. The hypothesis we consider here is that the spartaeine species that are proficient at solving prey-capture problems are also proficient at solving novel problems. We used nine species from this subfamily in our experiments. Eight of these species (two Brettus, one Cocalus, three Cyrba, two Portia) are known for specialized invasion of other spiders’ webs and for actively choosing other spiders as preferred prey (‘araneophagy’). Except for Cocalus, these species also use trial-and-error to derive web-based signals with which they gain dynamic fine control of the resident spider’s behaviour (‘aggressive mimicry’).The ninth species, Paracyrba wanlessi, is not araneophagic and instead specializes at preying on mosquitoes. We presented these nine species with a novel confinement problem that could be solved by trial and error. The test spider began each trial on an island in a tray of water, with an atoll surrounding the island. From the island, the spider could choose between two potential escape tactics (leap or swim), but we decided at random before the trial which tactic would fail and which tactic would achieve partial success. Our findings show that the seven aggressive-mimic species are proficient at solving the confinement problem by repeating ‘correct’ choices and by switching to the alternative tactic after making an ‘incorrect’ choice. However, as predicted, there was no evidence of C. gibbosus or P. wanlessi, the two non-aggressive-mimic species, solving the confinement problem. We discuss these findings in the context of an often-made distinction between domain-specific and domain-general cognition.