Plan B on the reef: Rising temperatures induce a prey shift in Drupella cornus from Acropora to Pavona in Mauritius, Western Indian Ocean

Abstract

Excessive corallivory by gastropods of the genus Drupella is an emerging threat causing considerable coral loss in the Indo-Pacific. However, the prey preferences around Mauritius in the Western Indian Ocean remain poorly understood, particularly under warming ocean conditions. This study assessed the distribution of Drupella cornus and the effect of temperature on its coral prey preference. Field surveys were conducted in December 2022 at two sites, namely, Le Bouchon and Grand Gaube, while ex-situ feeding experiments with the gastropods and corals were performed at 26°C, 29°C, and 32°C to simulate thermal stress. Field observations revealed a density of 122.80 ± 31.30 individuals m⁻² at Le Bouchon and 2.13 ± 0.46 individuals m⁻² at Grand Gaube. In situ, Drupella spp. were mainly found on Pavona spp., branching Acropora sp., massive Porites lutea and branching Porites sp. Experimental prey preference trials for Drupella feeding on corals corroborated field observations: across all three temperature categories combined, 11.11 ± 15.16% and 5.55 ± 6.82% individuals were attracted to branching A. muricata and massive Porites lutea, respectively. At 32°C, Pavona cactus hosted the highest percentage of D. cornus (11.67 ± 12.58%). This study highlights the adaptive response of D. cornus in terms of prey switching and a hierarchical feeding strategy, putting resilient coral species at risk of predation in the aftermath of bleaching events. Unlike many Indo-Pacific nations, Mauritius currently lacks a formal monitoring programme for Drupella, making these findings critical for informing future coral reef management strategies.