Evaluating risk-taking behaviors in Lycosidae: are the nutritional benefits of sugar water worth the risk of predation?

Abstract

The risk-taking tendencies and addiction in small vertebrates are often used to understand the processes of larger vertebrates, such as humans. We set out to find whether certain risk-taking behaviors characteristic of addiction remain consistent between vertebrates and invertebrates. Different animals will gorge on sugar water, and addiction-like tendencies are often associated with the overconsumption of sucrose. The goal of my study was to evaluate those risk-taking behaviors and compare invertebrate risk-taking behaviors to vertebrate risk-taking behaviors. The risk-taking behavior we observed was the process of relieving cravings while the risk of predation was present. Through this study we document evidence of wolf spiders feeding on a 25% sucrose solution and explain the wolf spiders preference to a sugar water solution over filtered tap water. To evaluate if wolf spiders exhibit addiction like behaviors associated with sucrose, we placed a green-colored, sugar water-soaked cotton ball on the silk of a large, predatory Tigrosa helluo wolf spider and a regular, filtered water-soaked cotton ball on the "safe" side of a plastic trial arena and then evaluated the behaviors of the prey spiders. We used a mixture of Pardosa milvina and Rabidosa rabida as test spiders, with one group given a sugar-water treatment beforehand and the other group was given a green colored control cotton ball with filtered tap water (n=14 for both the sugar water treatment and control groups). The wolf spiders who were predisposed to the sugar water treatment were more likely to cross through their predators silk in order to gain access to the sugar water cotton ball than their counterparts who were not given a sugar water treatment prior. These results suggest the risk for predation of the wolf spider is not worth the benefits of the sugar water, unless a wolf spider has been allowed unlimited access to sugar water in advance. When a wolf spider who was allowed unlimited access to sugar water beforehand is presented with a risky situation, they will increase their risk-taking behaviors via crossing through a predators silk in order indulge in the sugar water. These results suggest the addictive properties of sugar spans across vertebrates and invertebrates, and potentially opens the door for a cost-efficient and ethically acceptable invertebrate model-organism for examining the risk-taking behaviors associated with addiction.