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

Abstract

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.

Fig 1

Apparatus used for ascertaining capacities of spartaeine salticids to solve a novel confinement problem by using trial-and-error. In a water-filled tray (360 mm × 360 mm), there is an island (20 mm × 20 mm) surrounded by an atoll (200 mm × 200 mm, 10 mm thick). The test spider emerges from a hole (diameter 10 mm) in the island and the makes its first choice (i.e. either it leaps or it swims away from the island). Before testing begins, we determine at random which of the two potential choices will be successful. When the test spider makes the choice we predetermined to be the successful choice, we moved it to the atoll. When the test spider makes the choice we predetermined to be the unsuccessful choice, we returned it to the island. After a successful first choice, the spider can make its second choice from the atoll. After an unsuccessful first choice, the spider must make its second choice from the island

Fig 2

Number of test spiders that leapt or swam on their first attempt to cross water in Experiment 1

Fig 3

Results from Experiment 1 (on island surrounded by an atoll in tray of water, test spider given two opportunities to choose its method of crossing the water)

Fig 4

Pooled data for aggressive-mimic and non-aggressive-mimic spartaeine species (Experiment 2). Test spider was on island surrounded by an atoll in tray of water, and given up to 10 opportunities to switch after leaving the island and failing to succeed at reaching the atoll. Score: number of failures before switching (spiders that switched sooner got lower scores)