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Physiol Behav. 2019 Feb 1;199:182-190. doi: 10.1016/j.physbeh.2018.10.016. Epub 2018 Oct 30.

Environmental and physiological determinants of huddling behavior of molting female southern elephant seals (Mirounga leonina).

Author information

1
Laboratoire MECADEV, UMR 7179 CNRS/MNHN, 1 avenue du petit château, 91800 Brunoy, France. Electronic address: laureline.chaise@edu.mnhn.fr.
2
Scottish Centre for Ecology and the Natural Environment, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Rowardennan, Glasgow G63 0AW, UK.
3
Laboratoire MECADEV, UMR 7179 CNRS/MNHN, 1 avenue du petit château, 91800 Brunoy, France.
4
Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, UK.
5
Université de Strasbourg, CNRS, IPHC UMR 7178, 67000 Strasbourg, France.
6
Ecole Nationale Vétérinaire d'Alfort, Ethologie, 7 avenue du Général de Gaulle, 94700 Maisons-Alfort, France; Laboratoire MECADEV, UMR 7179 CNRS/MNHN, 1 avenue du petit château, 91800 Brunoy, France.

Abstract

While endotherms can rely on their insulation to reduce heat loss to adapt to cold environments, renewing of fur during molt impairs insulation while they have to perfuse the periphery to support epidermal tissues. The southern elephant seal Mirounga leonina undertakes an annual catastrophic molt while fasting on land in a wet, windy and cold environment. However, southern elephant seals show characteristic aggregation patterns that are predicted to reduce high metabolic costs during the molt. Between 2012 and 2016, 59 female elephant seals were tracked on land during their molt to study their aggregation behavior in relation to molt stage, habitat type and local weather conditions. Infrared thermography and stomach temperature loggers were used to observe variation in body surface and internal temperature in relation to molt stage and aggregation behavior. We found that thermal constraints varied during the molt, with a peak in surface temperature during the mid-stage of the molt. Wallows (mud pools) appear as favorable habitat to aggregate while molting. Indeed, wallows offered a warmer microclimate with greater ground temperature and lower wind speed. Moreover, there was a greater proportion of aggregated seals and larger group size in wallows. These aggregation patterns in wallows were influenced by local weather such that a greater proportion of seals were located in the center of the aggregation, and larger group size occurred during days of unfavorable meteorological conditions. We also observed a higher proportion of seals at mid-stage of molt amongst aggregated seals compared to isolated individuals. This aggregation behavior may reduce the cost of thermogenesis as surface body temperature and stomach temperature were cooler by 1.0 °C and 1.5 °C, respectively, in aggregated compared to isolated seals. As a consequence, huddling behavior may be thermally advantageous for female southern elephant seals during the molt.

KEYWORDS:

Aggregation behavior; Habitat type; Heat loss; Meteorological variations; Phocids; Stomach temperature

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