Memory and cognition in dormice

Research project

He has been in hibernation since October and seemingly nothing can wake him up. But his inner clock is ticking, inevitably signalling the approaching end of the winter. For the edible dormouse (Glis glis), hibernation is an adaptive mechanism to deal with the cold season when food is scarce. But what effect does the months-long slowdown of almost all metabolic processes have on the little rodent’s memory, spatial orientation and cognition? A team of researchers led by Claudia Bieber from the Research Institute of Wildlife Ecology (FIWI) at Vetmeduni Vienna is looking into this question, researching memory retention in edible dormice.

Good to know: The Austrian League for Nature Conservation (Naturschutzbund Österreich) has named the edible dormouse Animal of the Year for 2021 as part of its effort to raise awareness of the threats to their habitat and their way of life.

As early as October, edible dormice literally go underground as they retreat into frost-free burrows to hibernate. Hibernation is an extreme adaptive strategy used by several mammal species to make it through the cold, barren months of winter or survive other adverse environmental conditions. During hibernation, the animals go into torpor phases in which the metabolism slows significantly and body temperature drops to ambient levels – possibly even reaching zero degrees Celsius. Heart rate and respiration are extremely reduced, the brain shows almost no activity and cerebral blood flow is greatly decreased.

To survive their long hibernation, edible dormice regularly interrupt their weeks-long torpid state and reactivate their metabolism for a few hours. During these arousal phases, the metabolism works at full speed. The body temperature reaches almost normal levels, and the respiratory and heart rates increase. About eight hours later, the animals return to a torpid state.

Are arousal phases good for memory retention and recall?

A new FWF-funded research project conducted by the Research Institute of Wildlife Ecology (FIWI) at Vetmeduni Vienna is investigating the effects that hibernation has on memory retention and cognition in edible dormice. Do the animals have to rediscover and relearn their environment every year after waking up in the spring? Do they recognize their relatives and the members of their group? “Previous studies have failed to provide a clear picture in this regard, but research suggests that hibernation may have negative effects,” says wildlife ecologist Claudia Bieber. To date, it remains unclear why hibernators repeatedly interrupt the torpid state with short periods of arousal. Could these short waking phases contribute, among other things, to the maintenance of spatial orientation and cognitive abilities?

“Using a series of experiments, we want to investigate exactly what influence different factors of hibernation – the frequency of arousals, a minimum body temperature, and/or the entire duration of the hibernation – have on memory and cognition in hibernators,” Claudia Bieber explains.

Since dormice show extreme long hibernation durations, this species is an especially interesting subject for memory and cognition research. These rodents spend on average eight months of the year in hibernation and have even been shown to hibernate for 11 months in extreme cases. Thus, if hibernation has a negative impact on memory retention and orientation, edible dormice would be particularly affected. Moreover, the animals live in the tree canopies when active, and an arboreal lifestyle requires a high level of spatial coordination.

Animals to be tested after hibernation

The researchers plan to use innovative techniques and state-of-the-art technology in their study, as Claudia Bieber explains: “The animals will be implanted with tiny data loggers to record their seasonal activity and body temperature over a period of two years. This will allow us to exactly track the body temperature of the dormice and their activity patterns at all times.” Before the animals go into hibernation, they will be trained to navigate a maze and find their way out. The dormice will learn to recognize different symbols and to locate the exit by jumping on the correct symbol. After the end of the hibernation in spring, the researchers will test the animals to determine whether they can remember the right way out of the maze and whether they recognize the symbols learned prior to hibernation. “We also want to house some animals together in groups in large outdoor enclosures. Here they will have the opportunity to share their sleeping places in nest boxes with other dormice during the active season. Using social network analysis, we plan to investigate whether hibernation affects group formation,” Claudia Bieber says in closing.

The research project is being funded by the Austrian Science Fund (FWF). Scheduled start of project: February 2021.

Wissenschaftliche Ansprechpartner:

Claudia Bieber
Research Institute of Wildlife Ecology (FIWI)
University of Veterinary Medicine Vienna (Vetmeduni Vienna)
Claudia.Bieber@vetmeduni.ac.at

Originalpublikation:

The research project is being funded by the Austrian Science Fund (FWF). Scheduled start of project: February 2021.

Weitere Informationen:

https://www.vetmeduni.ac.at/en/infoservice/press-releases/presseinformationen-20…