Thermal ecology and social thermoregulation of Southern elephant seals (Mirounga leonina) during their moult

• Main Author: Chaise, Laureline
• Other Authors: Mécanismes Adaptatifs et Evolution (MECADEV), Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS), Museum national d'histoire naturelle - MNHN PARIS, Marc Théry, André Ancel, Caroline Gilbert
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2017
• Subjects: Phocidae; Huddling; Heat loss; Movements; Habitat use; Body condition; Phocidés; Agrégation; Pertes thermiques; Déplacements; Sélection de l'habitat; Condition corporelle; [SDV.BA]Life Sciences [q-bio]/Animal biology; Huddle; Wallows; Elephant Seals; Mirounga leonina; Southern Elephant Seals
• Online Access: https://theses.hal.science/tel-01951500; https://theses.hal.science/tel-01951500/document; https://theses.hal.science/tel-01951500/file/VA_CHAISE_Laureline_08122017.pdf

Annual life cycle of Phocids at sea is interrupted twice for reproduction and moult on land. The moult, an energetically costly phase, is essential for the renewal of hair, as well as epidermis in some monachine seals (Mirounga and Monachus). Southern elephant seals (Mirounga leonina) huddle in mud pools, or “wallows”, while moulting on land. Peripheral vasodilatation through the isolating layer of the blubber to renew skin cells during the moult creates major heat loss, that’s why this species moult on land, fasting, rather than staying in water. Many bird and mammal species developed an energy saving strategy based on social thermoregulation in order to decrease heat loss, especially in extreme environments or particular physiological stages. However, few studies have investigated behavioural and physiological adaptations of southern elephant seals during the moult. Our study rests on the hypothesis that huddling behaviour of moulting elephant seals follows the same determinants and allows equivalent thermal and energetic benefices than social thermoregulation. We studied behavioural adaptations on land of female southern elephant seals during five moult seasons, linked to local environmental and individual physiological variations. Our results show that habitat selection, distances moved on land and aggregation behaviour are influenced by the stage of the moult, the habitat type and meteorological conditions. At the peak of moult, heat loss and aggregation behaviour are both increased, as movements on land are decreased. Moreover, aggregation rate and aggregations size increase when local weather is deteriorated, mainly in “wallows”. However, distances moved increase when windchill is low or solar radiation is high. Furthermore, aggregated seals have a lower body temperature (skin and stomach) than isolated seals. The elevated metabolic rate observed would be linked to thermal constraints and an elevated hormonal metabolism. Although we found no correlation between aggregation and body mass loss, individual ...