The mass-dependent predation risk (MDPR) hypothesis poses an animal's body mass as a trade-off between the risk of starvation and the risk of predation. For instance, an animal with more body mass would be less at risk of starvation, but this increased weight may impede their ability to get away. This concept is especially relevant to wolf spiders, which don't build webs but actively hunt down their prey out in the open. Larger wolf spiders like Tigrosa helluo can extract and respond to information about the hunger levels of their smaller wolf spider prey, Pardosa milvina. In previous research, T. helluo required more attacks to capture hungry prey, which weighed significantly less than satiated spiders. Elaborating on this result, we hypothesized that lighter, hungry wolf spiders may exhibit higher escape performance, making them harder to catch. We filmed the escape behavior of hungry and satiated P. milvina with a high-speed camera. This footage was analyzed in a machine learning program to extract the spider's speed, acceleration, jump height, and whether they moved before contact during a simulated predation attempt. Hungry P. milvina weighed less, moved before contact more often, and achieved a greater maximum speed than when they were satiated. This confirmed our hypothesis that hungry prey exhibit a higher escape performance. Our study supports the MDPR hypothesis with implications for predator-prey interactions among wolf spiders and the decision-making therein, as wolf spiders adapt to their food-limited environment to reduce predation risk at lower body mass.
Acknowledgements: This research was made possible by the Peter R. Brayton Summer Research Fellowship.