Influence of energetic state on individual variation in boldness in the jumping spider Eris militaris (Araneae: Salticidae)

Feedback loops between an animal’s state (e.g., its energy balance) and its behavior have been proposed as a potential explanation for personality differences. Depending on the type of relationship between behavior and state, feedback loops may either amplify or erode behavioral variation over time. We tested the presence of such a feedback mechanisms using the jumping spider Eris militaris as model organism using a two-part experiment. First we investigated the influence of energy balance on an individual’s boldness. Individuals were randomly assigned to a low-energy or high-energy feeding regime. We used video playback to simulate exposure to a large jumping spider predator and compared the reaction time and the approach distance to the predator between feeding regimes. Second, we investigated the relation between boldness and energy acquisition. We repeatedly tested individuals for boldness and correlated their mean boldness score with their latency to capture a prey item (adult Drosophila hydei) in presence/absence of a predator and their feeding rate (number of captures in presence of 10 adult Drosophila melanogaster during 1 h). We found evidence for an interaction between sex and feeding regime in our first experiment, indicating that males were bolder when well fed while the opposite trend was found for females. We also found a positive boldness-prey capture correlation in females only.