Predation risk, stress, and life history tactics of edible dormice

Edible dormice with young in a nest box
Photo of edible dormice with young in a nest box 1
 
Dormice are good climbers
Photo of dormice are good climbers 2
A young dormouse
Photo of dormice are good climbers 3
A nest box
Photo of a young dormouse 4
Hanging up a nest box
Photo of a dormouse nest box 5
On the lookout
Photo of researcher hanging up a nest box on a tree 6
Checking nest boxes
Photo of formouse looking out of a nest box 7
DNA extraction from dormouse saliva
Photo of researcher checking nest boxes 8
Fall in the Vienna Woods
Photo of lab DNA extraction from dormouse saliva 9

Living with pulsed resources

The exact timing of producing offspring is an important factor for an animal’s lifetime reproductive success. In seasonal environments reproduction is typically linked to the spring and summer season, when food availability is high. However, not all food resources are that easy to predict. Various terrestrial ecosystems are characterised by “pulsed resources”, i.e., occasional, short periods of resource superabundance. The edible dormouse (Glis glis), a small, arboreal hibernator, shows several remarkable adaptations to fluctuations in seed production of trees, and life-history characteristics related to pulsed resource exploitation. Dormice litter only once per year in July/ August, which is extremely late in the active season, compared to other hibernators. Reproduction just in time with the availability of ripe, high-caloric seeds on tree branches apparently optimizes survival and pre-hibernation fattening of their young. The disadvantage of this highly specialized adaptation is that in years without beechnuts or acorns the survival of juveniles would be very low. Hence, dormice skip reproduction in years without seed production.

Pathways of reproductive decisions

It seems that the availability of energy-rich food (seed buds) in spring represents an environmental signal to which dormice adjust their reproduction. At present, it is entirely unclear, however, by which pathway this signal translates into reproductive success or failure. Here, we are testing the hypothesis that effects of food quality on reproduction in dormice are linked to a factor that has never been considered before in this context, their exposure to predation pressure. Specifically, we hypothesize that access to energy-rich food (in years of mast seeding) allows the animals to minimize foraging time and hence exposure to predators, which can be a major stressor. We suggest that dormice are an excellent model to study the ‘Chronic Stress Hypothesis’ which predicts that the stress profile of an animal, and its physiological consequences, result from simultaneous effects of both food requirements and predation pressures, caused by the trade-off between the need to forage and to avoid predators. We therefore measure the time spent foraging (via transponder systems) and the concentration of faecal cortisol metabolites in a dormouse population in the Vienna Woods.

Escaping below ground

For dormice, which forage in the canopy of woods, the major predators are nocturnal birds of prey, namely owls. One possible avenue of evading these predators altogether – at least in years of reproduction skipping – would be evasion by retreat into underground burrows. Due to the combination of estivation and hibernation, dormice can spend up to > 10 months per year in dormancy. Thus, they spend much more time in hypometabolism than climatic conditions or food resources would demand. These results led us to hypothesize that the primary cause for estivation is not reduction of energy expenditure but predator avoidance. We are recording body temperature in free-ranging dormice during summer seasons under different environmental conditions. In a supplemental feeding field experiment we are investigating the effect of seed availability on the occurrence of estivation, the daily time spent foraging, concentration of cortisol metabolites, and reproduction.

Hibernation, estivation, and life-history

Further, we are investigating the consequences of the combination of hibernation, estivation, and reproduction skipping on life history characteristics of dormice, specifically on ageing. We suggest that the major cause for slowed ageing and increased longevity in dormice is their extensive use of hibernation (on average 8 months per year) and occasional periods of estivation. These factors may interact with reproduction skipping in an additive or even non-additive way. To determine the effects of both dormancy and reproduction on rates of aging, we also measure seasonal changes in the length of telomeres (the DNA sequences that cap and protect the ends of eukaryotic chromosomes). 

 

Duration January 2013- December 2016

 
Dormouse habitat in autumn
Photo of dormouse habitat in autumn 10
 

Project partners

FWF logo

Sponsored by the Austrian Science Fund (FWF) Project Nr. P25023 11


 

Scientific contact at FIWI

A.Univ.Prof.Dr.rer.nat Thomas Ruf, Research Institute of Wildlife Ecology, Vetmeduni Vienna

T. +43 (1) 25077-7150

Email Thomas Ruf


 

General Contact

Reception

Savoyenstraße 1
A-1160 Wien

T +43 (1) 25077-7900
F +43 (1) 25077-7941

Email FIWI


 

HOME 12