title: Foraging in the darkness of the Southern Ocean: influence of bioluminescence on a deep diving predator.
abstract: How non-echolocating deep diving marine predators locate their prey while foraging remains mostly unknown. Female southern elephant seals (SES) (Mirounga leonina) have vision adapted to low intensity light with a peak sensitivity at 485 nm. This matches the wavelength of bioluminescence produced by a large range of marine organisms including myctophid fish, SES's main prey. In this study, we investigated whether bioluminescence provides an accurate estimate of prey occurrence for SES. To do so, four SES were satellite-tracked during their post-breeding foraging trip and were equipped with Time-Depth-Recorders that also recorded light levels every two seconds. A total of 3386 dives were processed through a light-treatment model that detected light events higher than ambient level, i.e. bioluminescence events. The number of bioluminescence events was related to an index of foraging intensity for SES dives deep enough to avoid the influence of natural ambient light. The occurrence of bioluminescence was found to be negatively related to depth both at night and day. Foraging intensity was also positively related to bioluminescence both during day and night. This result suggests that bioluminescence likely provides SES with valuable indications of prey occurrence and might be a key element in predator-prey interactions in deep-dark marine environments.
authors.affiliation: Centre d'Etudes Biologiques de Chizé (CEBC), CNRS UPR 1934, Villiers-en-bois, France. jadevacquiegarcia@gmail.com
authors.forename: Jade
authors.initials: J
authors.lastname: Vacquié-Garcia
authors.forename: François
authors.initials: F
authors.lastname: Royer
authors.forename: Anne-Cécile
authors.initials: AC
authors.lastname: Dragon
authors.forename: Morgane
authors.initials: M
authors.lastname: Viviant
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bailleul
authors.forename: Christophe
authors.initials: C
authors.lastname: Guinet
mesh_terms: D000054:Acceleration; D000465:Algorithms; D000818:Animals; D003624:Darkness; D004242:Diving; D004463:Ecology; D017753:Ecosystem; D005247:Feeding Behavior; D005260:Female; D005399:Fishes; D008027:Light; D049449:Luminescence; D009068:Movement; D009792:Oceans and Seas; D011235:Predatory Behavior; D046048:Seals, Earless; D013997:Time Factors