Jolivet A. auteur aut IRD Chauvaud L. auteur aut IRD Thebault J. auteur aut IRD Robson A. A. auteur aut IRD Dumas Pascal auteur aut IRD Amos G. auteur aut IRD Lorrain Anne auteur aut IRD text journalArticle eng text/pdf reformatted digital access Background: Behaviour and time spent active and inactive are key factors in animal ecology, with important consequences for bioenergetics. For the first time, here, we equipped the gastropod Tectus (= Trochus) niloticus with accelerometers to describe activity rhythms at two sites in the Southwest Pacific with different temperature regimes: New Caledonia and Vanuatu. Results: Based on a 24-hour cycle, T. niloticus activity began at dusk and gradually stopped during the night, before sunrise. This nocturnal behaviour was characterised by short (duration < 30 s), low intensity (acceleration < 0.12 g) movements and was probably associated with foraging behaviour. We assumed that activity ceased once the animal was satiated. Our analysis of two size groups in Vanuatu (80-90 mm vs. 120-140 mm, basal shell diameter) revealed a size effect; smaller specimens displayed greater activity, reflected by more intense and longer movements while migrating at night toward the edge of the reef. This nocturnal behaviour is not uncommon for grazing gastropods and is mainly associated with attempting to avoid visual predators whilst feeding. Conclusions: The use of accelerometers coupled with light and temperature sensors provided detailed information on topshell behaviour and physiology under natural conditions. These data provide a foundation for identifying potential changes in the fine-scale behaviour of T. niloticus in response to environmental changes, which is essential in animal ecology and stock conservation. specialized INVERTEBRE AQUATIQUE RYTHME BIOLOGIQUE MIGRATION PHYSIOLOGIE ANIMALE ACCELEROMETRIE Activity Accelerometry 24-hour periodicity Tectus niloticus Foraging Migration PACIFIQUE NOUVELLE CALEDONIE VANUATU 036MILMAR 3 art. 26 [12 ] 2015 2051-3933 https://www.documentation.ird.fr/hor/fdi:010074439 10.1186/s40462-015-0054-5 2051-3933 [F B010074439] https://www.documentation.ird.fr/hor/fdi:010074439 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers18-11/010074439.pdf IRD - Base Horizon / Pleins textes 2018-12-06 2019-02-06 fdi:010074439 fre