Wherever you’re reading this from, whether it be your home, the library, wherever, you had to navigate to your current location. We don’t typically think of this as navigation as it usually requires minimal effort when following known routes. But what if I asked you to find the quickest or an alternate way to walk between where you just came from and here? These shortcuts require a bit of additional information, and environmental cues pertaining to distance and your ability to traverse certain terrains.
This simple task of route identification was recently presented to two species of jumping spiders, the Portia and Trite, and the results are strikingly human.
To test the spiders’ skills, researchers established a couple experiments in which jumping spiders were placed in the center of a pool of water (which the spiders naturally have an aversion to) and had the ability to choose different paths to safety which were constructed with a series of wooden dowels one centimeter in diameter each, leading from the center of the pool to dry land.
In the first experiment, they constructed a dowel layout that had varying distances between each dowel to determine if the spider could sense or perceive the risk associated with the longer jumps that had to be taken on any one route. The paths with longer jumps and fewer dowels obviously more room for error and thus were considered more dangerous. However, in retrospect, the researchers stated that for the Trite this was likely an underwhelming distance, and below their “danger threshold”.
In the second experiment, the researchers wanted to home in on the spiders’ ability to differentiate between the lengths of paths presented. The distance between the dowels was controlled, but the path length was variable. These alternative paths also present the potential for shortcuts, or path jumping due to the proximity of dowels for separate paths as seen in the illustration below.
So, how’d these jumpers do? Portia females chose the safer routes more often than the risky routes, but their male counterparts, surprisingly, had no preference. Trite females similarly had no preference, while Trite males never selected the safe route. This may have been due to the jumping ability of any one spider, but further tests would have to be done to verify this prediction.
The risk aversion of the Portia species of jumping spiders was also noticeable in the second experiment as they overall opted for shorter routes and were significantly more likely to create novel routes (or shortcuts) from the original paths outlined by researchers.
You may be asking yourself, sure that’s cool, but why does it matter? Well, this is a critical step in understanding the perceptual fields of jumping spiders, and their decision-making process based on the complexity of their environments. The differences better Portia and Trite also exemplify underlying discrepancies within either their ability to perceive that spatial tasks in front of them or that they can simply jump further and see that their threshold distance for jumping is longer than the riskiest assessment given to them.
On top of this, the ability to discover new, novel routes is an interesting feature of these spiders’ decision-making process that is worth further exploration.
These experiments serve as a baseline for further inquiry into the sensory systems of these jumping spider species. For instance, what if the dowels were randomly moving around the pool, does the spider create a map in its head from the center of the pool or is it constantly updating? Or, what if the spider was partially blindfolded, would they choose less risky paths? Or, if their jump was somehow hindered or amplified, would that affect their confidence in jumps? The work done throughout these experiments, while relatively simple, opens up a new set of questions surrounding creative and adaptive path-building processes. It also highlights an interesting correlation between sensory systems and the environment directly.
We typically discuss the environment as a tool to increase protection from predation or to modulate the call or warning signals of any individual. Yet this study pits these spiders directly against their environment which also points to the emphasis that we put on the selective pressure of predation rather than other inherent ecological risks, which we may start to see more frequently as landscapes alter due to global climate change.
References: Aguilar-Argüello, S., Gerhard, D., & Nelson, X. J. (2019). Risk assessment and the use of novel shortcuts in spatial detouring tasks in jumping spiders. Behavioral Ecology, 30(5), 1488–1498. doi: 10.1093/beheco/arz105