Daily Variation in the Feeding Activity of Pacific Crown-of-Thorns Starfish (<i>Acanthaster</i> cf. <i>solaris</i>).

Abstract

The ecological impact of crown-of-thorns starfish (CoTS; <i>Acanthaster</i> spp.) on coral reefs is intrinsically linked to their feeding behaviour. Management thresholds designed to mitigate coral loss driven by elevated densities of crown-of-thorns starfish rely on accurate estimates of individual feeding rates. In this study, structure-from-motion photogrammetry and intensive tracking of adult Pacific CoTS over an extended survey period were used to generate three-dimensional, high-resolution estimates of daily feeding rates. Our findings revealed substantial variation in the areal extent of coral consumed, both across consecutive days and among individuals. Notably, CoTS did not feed consistently; feeding occurred on 65% of observation days, with 2-3 days periods of inactivity common. Despite this variability, mean daily feeding rates aligned with previous studies (1.35 coral colonies d^-1; 198.4 cm² day^-1 planar area, and 998.83 cm² day^-1 three-dimensional surface area). Across all tracked individuals (n = 8), feeding was recorded on 17 coral genera; however, <i>Acropora</i> alone accounted for 51% of colonies consumed and contributed 82% of the total three-dimensional surface area ingested during the survey period. This highlights the disproportionately large feeding yield derived from <i>Acropora</i>-dominated diets and raises important questions about how future declines in <i>Acropora</i> cover may impact CoTS feeding success and energetic intake.