title: Food selectivity and diet switch can explain the slow feeding of herbivorous coral-reef fishes during the morning.
abstract: Most herbivorous coral-reef fishes feed slower in the morning than in the afternoon. Given the typical scarcity of algae in coral reefs, this behavior seems maladaptive. Here we suggest that the fishes' slow feeding during the morning is an outcome of highly selective feeding on scarcely found green algae. The rarity of the food requires longer search time and extended swimming tracks, resulting in lower bite rates. According to our findings by noon the fish seem to stop their search and switch to indiscriminative consumption of benthic algae, resulting in apparent higher feeding rates. The abundance of the rare preferable algae gradually declines from morning to noon and seems to reach its lowest levels around the switch time. Using in situ experiments we found that the feeding pattern is flexible, with the fish exhibiting fast feeding rates when presented with ample supply of preferable algae, regardless of the time of day. Analyses of the fish's esophagus content corroborated our conclusion that their feeding was highly selective in the morning and non-selective in the afternoon. Modeling of the fishes' behavior predicted that the fish should perform a diel diet shift when the preferred food is relatively rare, a situation common in most coral reefs found in a warm, oligotrophic ocean.
authors.affiliation: The Interuniversity Institute for Marine Sciences of Eilat, Eilat, Israel ; Department of Ecology, Evolution & Behavior, the Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Ruth
authors.initials: R
authors.lastname: Khait
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel Aviv, Israel.
authors.forename: Uri
authors.initials: U
authors.lastname: Obolski
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel Aviv, Israel.
authors.forename: Lilach
authors.initials: L
authors.lastname: Hadany
authors.affiliation: The Interuniversity Institute for Marine Sciences of Eilat, Eilat, Israel ; Department of Ecology, Evolution & Behavior, the Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Amatzia
authors.initials: A
authors.lastname: Genin
mesh_terms: D000818:Animals; D057894:Coral Reefs; D004032:Diet; D005247:Feeding Behavior / Q000502:physiology*; D005399:Fishes / Q000502:physiology*; D005518:Food Preferences / Q000502:physiology*; D060434:Herbivory / Q000502:physiology*