Nature
Known as jumping spiders, members of the Salticidae family of arachnids are remarkable for more than just their ability to leap through the air. Among their many impressive attributes is a level of cognizance rarely seen in creatures of their diminutive size, which enables them to plan ahead and work out the most appropriate route to catch their prey.
This ability had previously been studied in one particular species of jumping spider, known as Portia fimbriata, although researchers from the University of Canterbury wanted to know if other species of jumping spider boasted a similar cognitive capacity. According to their results, published in the Journal of the Experimental Analysis of Behavior, at least 15 species show evidence of forward planning.
For the investigation, the researchers set up an obstacle course for the spiders, in which they were first placed on a tower surrounded by water, from where they had a clear view of two boxes in the distance. One of these boxes contained fragments of other spiders on which the test subjects are known to prey, while the other did not.
Having been starved for a week before the experiments began, the spiders were all hungry, although the researchers made sure to use species that they knew had an aversion to water, and would therefore not risk getting wet in order to reach their prey. In total, 15 different species of Salticidae were subjected to the obstacle course, all of which came from the spider-eating Spartaeinae subfamily.
In order to obtain their prey, the spiders had to choose from two different trails, one of which led to the empty box while the other led to the box containing food. However, since both paths were winding, the spiders could not see their target while they walked, meaning they would have to remember its location in order to discern the correct detour.
To make things harder, the spiders often had to walk past the incorrect trail before reaching the correct one, and would therefore have to be relatively sure of where they were going and ignore the wrong turns.
Detailing their findings, the study authors report that “all 15 species chose the correct walkway significantly more often than the incorrect walkway.” They subsequently conclude that the spiders are capable of “genuine cognition,” with a working memory that allows them to maintain a mental representation of where their prey is located even when it is no longer visible.
This finding is reinforced by the fact that those spiders that chose the wrong path tended to pause in confusion once they realized their error, suggesting that they had maintained an expectation of encountering the previously seen prey throughout their journey.
In light of their fascinating findings, the researchers declared it "likely that a capacity for planned detouring is unlearned and widespread, if not universal, among araneophagic spartaeines."
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