Diel shift of king penguin swim speeds in relation to light intensity changes

• Published in: Marine Ecology Progress Series
• Main Authors: Shiomi, Kozue, Sato, Katsufumi, Handrich, Yves, Bost, Charles-André
• Other Authors: National Institute of Polar Research Tokyo (NiPR), Atmosphere and Ocean Research Institute Kashiwa-shi (AORI), The University of Tokyo (UTokyo), Département Ecologie, Physiologie et Ethologie (DEPE-IPHC), Institut Pluridisciplinaire Hubert Curien (IPHC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: Vision; Movement; Diving behaviour; Foraging; Diel cycle; Bio-logging; Penguins; [SDE]Environmental Sciences; King Penguins
• Online Access: https://hal.archives-ouvertes.fr/hal-01444616; https://doi.org/10.3354/meps11930

International audience It is generally expected that animals, including marine organisms, travel at speedsachieving the minimum energetic cost of transport. However, several factors cause variation inspeeds within the energetically acceptable range. Light intensity is known to affect movementspeeds in some flying and walking insects, which reduce speeds at low light levels. This isexplained as compensation for degraded temporal resolution of vision in dim light by maintainingthe rate of information gained per unit of travelling distance. Such a relationship between ambientlight intensity and movement speeds is expected for any visual system in principle, but has notbeen examined in any marine species. As a mesopelagic forager, king penguins Aptenodytespatagonicus regularly commute between their breeding colonies and productive foraging areasover several hundreds of kilometres. During these trips, they experience a wide variation in lightintensity between day and night, as well as within daylight hours, as dives often reach deeperthan 100 m. The present study investigated diel patterns in the swim speeds of king penguins inrelation to light intensity experienced within dives. King penguins gradually decreased theircruising speeds around dusk and increased them again around dawn. This resulted in consistentlyslower speeds in nocturnal dives. Correspondingly, the underwater light levels estimated werealways higher in diurnal dives, even at depths greater than 100 m. The slower swim speeds afterdusk may facilitate travelling and occasional prey detection in the dark. These results suggest thata common behavioural response to ambient light levels has evolved in different taxa of animals.