Presenter: Britney R. Lyons

Faculty Sponsor: Beth Jakob

School: UMass Amherst

Research Area: Biology

Session: Poster Session 6, 4:15 PM - 5:00 PM, 165, D5

ABSTRACT

Numerical competence, the ability to judge quantity, supports important decisions such as choosing food, avoiding predators, and joining groups. Although documented in vertebrates, less is known about how small-brained predators use numbers in hunting or how attention limits this skill. Jumping spiders (Salticidae) must integrate information from eight eyes, making them well-suited to test how quantity and distraction interact. In Experiment 1, we test whether spiders use prey group size to guide foraging. Spiders (N=40) choose between groups of crickets trapped behind transparent barriers and differing in number (1,2,4, and 8, in pairwise comparisons). We predict that spiders will orient towards larger groups because motion attracts their attention, but attack smaller groups because individual prey are easier to track. In Experiment 2, spiders (N=30) are placed in the same arena with cricket groups of different sizes (1, 2, or 4). Half of the spiders have their posterior lateral eye masked to reduce the detection of distracting movement. We hypothesize that spiders are distracted in larger groups of prey because movement behind them interrupts their predatory approach. We predict that unmasked spiders will be interrupted in their attacks more frequently with larger groups of prey, and that masked spiders will be interrupted in their attacks less often than unmasked spiders. These findings will clarify how invertebrate visual systems process quantity and how attention shapes numerical decision-making in natural environments.