ORCID

0000-0003-3547-1614

Keywords

Chronobiology, Gymnotiformes, landscapes of fear, lunar rhythm, risk-sensitive foraging, visual ecology

Abstract

Animals must forage to acquire energy for survival and reproduction, yet foraging exposes them to predators. This creates a trade-off between energy intake and safety, wherein the perception of predation risk alone can alter activity patterns. Within this trade-off, risk, energetic needs, and sensory adaptations vary, shifting the balance and favoring different foraging strategies. Using Neotropical electric fish as a study system, I investigated how foraging under predation risk is shaped across biological scales, including environmental dynamics, interspecific sensory differences, activity-timing mechanisms, and intraspecific variations. These nocturnal fish emit continuous electric signals to sense their environment, allowing non-invasive monitoring of activity through signal recording. Because they are generally light-averse, moonlight serves as a quantifiable proxy for perceived predation risk. I first developed an R package and hardware system to predict and recreate moonlight cycles. Next, I tested whether eye size, a proxy for visual acuity, predicts interspecific differences in moonlight responses by deploying electric loggers in an Amazonian stream. Smaller eyes predicted stronger moonlight avoidance, whereas a large-eyed species lacked a moonlight response entirely. I then investigated the timing mechanisms of the sand knifefish, discovering that exogenous and endogenous mechanisms interact to guide activity across the complex moonlight cycle by dynamically tracking shifting dark periods. Lastly, I tested how risk-taking is influenced by body condition and life stage. In captive experiments, adults—but not juveniles—became more risk-prone as condition decreased. Collectively, this research shows how factors across biological scales shape animal behavior within a dynamic nocturnal landscape of fear.

Completion Date

2026

Semester

Spring

Committee Chair

Crampton, William

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Biology

Format

PDF

Document Type

Dissertation

Identifier

DP0053112

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