15.09.2022: The garden dormouse (Eliomys quercinus) is a slightly smaller relative of the edible dormouse. The highly endangered rodent uses hibernation - a series of multiple torpor bouts - as an adaptation strategy to the cold, low-food-availability season. The animals use two strategies for this, namely torpor and huddling (snuggling up against one another). According to a recently published study by the Vetmeduni´s Research Institute of Wildlife  Ecology, the behaviour of social thermoregulation pays off: The energy expenditure during the rewarming phase from torpor is significantly reduced by "huddling".

For their study, the scientists investigated the extent to which huddling helps garden dormice save energy. According to study lead author Laura Magaly Charlanne from FIWI at Vetmeduni, the energy-saving hypothesis was confirmed: "Huddling significantly reduces energy consumption during rewarming - the phase with the highest energy requirement during hibernation. Huddling animals reduced heat requirements and weight loss by two-thirds compared to animals waking up alone.”

Garden dormice share the benefits of body contact

On the downside, huddling does not reduce the weight loss of young animals over the entire hibernation period. A possible reason for this is that the animals take turns warming up, which could mitigate the energetic advantages of close body contact. Study last author Sylvain Giroud from FIWI says: "Our study of the dynamics of huddling revealed random-like behavior during hibernation, as awakening from torpor was not always initiated by the same animal. The garden dormice took turns within their group. Also, during the warm-up, the animal with the highest body temperature entered torpor later than the others in the group.”

Collective gains from energy savings

The conclusion of the scientists: The animals share the advantages and disadvantages of huddling and warming up on a collective level without deriving any individual energetic benefit from it. "We hypothesize that the dynamics of social thermoregulation during hibernation offset the individual benefits due to the reduced energy expenditure associated with the energy-intensive process of rewarming from torpor," says Sylvain Giroud.

Social thermoregulation and global change

According to the researchers, studies with varying group compositions are now needed to learn more about the strategy of social thermoregulation and to investigate possible long-term effects after several winters. This is also because due to the rapid global changes and the increasing occurrence of unpredictable weather events, new knowledge is urgently needed about the extent to which flexible energy saving strategies help to survive hibernators their seasonal hibernation.
 

The article "Sticking Together: Energetic Consequences of Huddling Behavior in Hibernating Juvenile Garden Dormice“ by Laura Magaly Charlanne, Sebastian Vetter, Joy Einwaller, Johanna Painer, Caroline Gilbert, and Sylvain Giroud was published in the special edition “Time Out for Survival: Hibernation and Daily Torpor in Field and Lab Studies” of the journal Physiological and Biochemical Zoology.

Scientifi article