Use of social thermoregulation fluctuates with mast seeding and reproduction in a pulsed resource consumer.

Edible dormice (Glis glis) can remain entirely solitary but frequently share sleeping sites with conspecifics in groups of up to 16 adults and yearlings. Here, we analysed grouping behaviour of 4564 marked individuals, captured in a 13-year study in nest boxes in a deciduous forest. We aimed to clarify (i) whether social thermoregulation is the primary cause for group formation and (ii) which factors affect group size and composition. Dormice temporarily formed both mixed and single-sex groups in response to acute cold ambient temperatures, especially those individuals with small body mass. Thus, thermoregulatory huddling appears to be the driving force for group formation in this species. Huddling was avoided-except for conditions of severe cold load-in years of full mast seeding, which is associated with reproduction and high foraging activity. Almost all females remained solitary during reproduction and lactation. Hence, entire populations of dormice switched between predominantly solitary lives in reproductive years to social behaviour in non-reproductive years. Non-social behaviour pointed to costs of huddling in terms of competition for local food resources even when food is generally abundant. The impact of competition was mitigated by a sex ratio that was biased towards males, which avoids sharing of food resources with related females that have extremely high energy demands during lactation. Importantly, dormice preferentially huddled in male-biased groups with litter mates from previous years. The fraction of related individuals increased with group size. Hence, group composition partly offsets the costs of shared food resources via indirect fitness benefits.

Evolutionary applications of phylogenetically-informed ecological niche modelling (ENM) to explore cryptic diversification over cryptic refugia.

We used the fat dormouse (Glis glis), a species from a monotypic genus of family Gliridae, as a model to promote the understanding of patterns of cryptic diversification along the ancient Hyrcanian Forests, one of the old-growth relicts of the temperate deciduous forests worldwide. Mitochondrial Cytb data was used to investigate the phylogenetic status of two geographically-different populations of G. glis along the Hyrcanian Forests among all the worldwide known lineages of the species. Regarding phylogenetically informed partitioning of occurrence data, we then used two analytically different ENMs (i.e. environmental-space and geographic-space) to address whether niche divergence conforms G. glis diversification over the study area. Phylogenetic reconstruction showed significant heterogeneity between other fat dormouse lineages and those belonging to the Hyrcanian Forests as well as within the two hypothesized cryptic groups in the study area. Quantifying niche differences using the two ENM frameworks additionally confirmed divergence between the two cryptic lineages by indicating niche conservatism. The integration of phylogeny and ENM in this study confirms the development of distinct cryptic species and suggests that the Hyrcanian Forests, a well-known Pleistocene refugium, might contain multiple cryptic refugia for small forest-dwelling species during paleontological oscillations.

It takes two to tango: Phagocyte and lymphocyte numbers in a small mammalian hibernator.

Immunity is energetically costly and competes for resources with other physiological body functions, which may result in trade-offs that impair fitness during demanding situations. Endocrine mediators, particularly stress hormones, play a central role in these relationships and directly impact leukocyte differentials. To determine the effects of external stressors, energetic restraints and competing physiological functions on immune parameters and their relevance for fitness, we investigated leukocyte profiles during the active season of a small obligate hibernator, the edible dormouse (Glis glis), in five different study sites in south-western Germany. The highly synchronized yearly cycle of this species and the close adaptation of its life history to the irregular abundance of food resources provide a natural experiment to elucidate mechanisms underlying variations in fitness parameters. In contrast to previous studies on hibernators, that showed an immediate recovery of all leukocyte subtypes upon emergence, our study revealed that hibernation results in depleted phagocyte (neutrophils and monocytes) stores that recovered only slowly. As the phenomenon of low phagocyte counts was even more pronounced at the beginning of a low food year and primarily immature neutrophils were present in the blood upon emergence, preparatory mechanisms seem to determine the regeneration of phagocytes before hibernation is terminated. Surprisingly, the recovery of phagocytes thereafter took several weeks, presumably due to energetic restrictions. This impaired first line of defense coincides with lowest survival probabilities during the annual cycle of our study species. Reduced survival could furthermore be linked to drastic increases in the P/L ratio (phagocytes/lymphocytes), an indicator of physiological stress, during reproduction. On the other hand, moderate augmentations in the P/L ratio occurred during periods of low food availability and were associated with increased survival, but reproductive failure. In this case, the stress response probably represents an adaptive reaction that contributes to survival by activating energy resources. In contrast to our expectation, we could not detect an amplification of stress through high population densities. Summarized, results of our study clearly reveal that the leukocyte picture of active edible dormice responds sensitively to physiological conditions associated with hibernation, reproductive activity and food availability and can be linked to fitness parameters such as survival. Thus edible dormice represent an excellent model organism to investigate regulatory mechanisms of the immune system under natural conditions.

Direct and indirect effects of climate and seed dynamics on the breeding performance of a seed predator at the distribution edge.

Marginal populations usually have low densities and are considered to be particularly vulnerable to environmental stochasticity. Using data collected in nest boxes, we analyzed the breeding performance of the edible dormouse (Glis glis), an obligate hibernating rodent and a seed predator in deciduous forests, in two populations at the distribution range's edge. Despite being only 20 km apart from each other, Montseny is a large patch of mixed deciduous forests (oaks and beech), whereas Montnegre would be the harshest habitat, that is, a small, isolated patch with only oaks. First, we studied the differences in climate and tree cover change in the two populations. Second, we analyzed the direct and indirect roles of local climate conditions and seed availability on breeding performance over 10 years in each population. Finally, we explored the influence of tree cover change on the occupancy dynamics in the two populations. Our results showed contrasting responses between populations: in Montseny, asynchronous seed production between oaks and beech precluded skip breeding, and breeding performance increased with seed availability. Furthermore, dormice in Montseny may use pollen production to anticipate the amount of beech nut resources and adjust their breeding effort. Boxes showed higher occupancy and colonization and fewer extinctions in Montseny than in Montnegre, where seed availability did not drive breeding performance. Results from Montnegre suggest that skip breeding was an adaptive response to a more pulsed, harsher environment. Here, females produced a similar number of pups than at Montseny. Long-term studies dealing with population responses in marginal habitats can lead to a deeper understanding of the capacities of organisms to adapt to harsh environments. Although local adaptation is frequently documented across various taxa, studies at the distribution edge may shed light on our still limited comprehension of the underlying mechanisms responsible for its occurrence.

Influences of Maternal Weight and Geographic Factors on Offspring Traits of the Edible Dormouse in the NE of the Iberian Peninsula.

The main goal of this study was to analyze the reproductive patterns of edible dormouse (Glis glis) populations in the northeast of the Iberian Peninsula using an 18-year period of data obtained from nest boxes collected between 2004 and 2021. The average litter size in Catalonia (Spain) was 5.5 ± 1.60 (range: 2-9, n = 131), with litter sizes between 5 and 7 pups as the more frequent. The overall mean weight in pink, grey and open eyes pups was 4.8 g/pup, 11.7 g/pup and 23.6 g/pup, respectively. No differences in offspring weights between sexes were found in any of the three age groups. Maternal body weight was positively associated with mean pup weight, whereas no correlation between the weight of the mothers and litter size was found. The trade-off between offspring number and size was not detected at birth. Regarding litter size variation across the geographic gradient (and their climatic gradient associated) from the southernmost populations of the Iberian Peninsula located in Catalonia to the Pyrenees region in Andorra, no evidence to suggest that geographic variables affect litter size was found, discarding (1) an investment in larger litters to compensate shorter seasons related to higher altitudes or northern latitudes, and (2) variation in litter size related to weather changes (e.g., temperature and precipitation) along latitudinal and/or altitudinal gradients.

Fatty Acid Composition of M. Biceps Femoris of Edible Dormouse (Glis glis L.).

This study aimed to investigate the fatty acid (FA) composition of edible dormouse m. biceps femoris in both sexes. More than 20 FA were identified in the muscle, with the 18:1cis-9 (oleic acid) being the most abundant in both sexes, comprising more than 50% of total FA in muscle. The most dominated FA were monounsaturated (MUFA), followed by saturated FA (SFA) and polyunsaturated FA (PUFA), reaching 54.8%, 25.43% and 19.8% of total FA, respectively. Sums of PUFA and n-3 PUFA tended (p > 0.05) to be higher in males than in females. There were no significant differences between sexes on the FA composition. Nevertheless, the 18:2n-6 tended to differ between sexes (p = 0.063). Several long-chain PUFA (LC-PUFA) were detected in dormouse muscle, with the 20:4 n-6 (arachidonic acid, AA) and the 22:6 n-3 (docosahexaenoic acid, DHA) being the most abundant in both sexes. The relatively high stearoyl-CoA desaturase (SCD) indexes and the large concentration of 18:1cis-9 in dormouse muscle tissues might point to a low mobilization of the SCD products. Furthermore, finding the unusual FA 20:3 ∆5,∆11,∆14, suggests feeding on leaf and wood lipids of Coniferophytes. We demonstrated sexual size monomorphism in edible dormouse. The literature regarding the composition of dormouse meat is scarce and no studies reported the FA composition of muscle, thus, this work can contribute to increasing the knowledge on edible dormouse physiology and nutritional traits.

Monitoring Campaign over an Edible Dormouse Population (Glis glis; Rodentia: Gliridae) in Sicily: First Report of Mesocestodiasis.

This study reports on the health status of the edible dormouse (Glis glis) living in Nebrodi Park (Sicily, Italy), responsible for nut crop damage in the area. In the frame of a monitoring campaign for potential zoonotic risk involving 30 dormice, rectal and conjunctival swabs and fur and nest content were collected for bacteriological and parasitological examinations, respectively. A large presence of fleas belonging to Monopsyllus sciurorum was found. Necropsy of a dead dormouse revealed an infection of Mesocestoides lineatus, whose cysts were found in the abdomen cavity and on the liver; this is the first report of this in this species. Further studies are necessary to identify their role in the environment, considering the limited knowledge of this species in Italy.

Life history written in blood: erythrocyte parameters in a small hibernator, the edible dormouse.

The oxygen delivery system is one major determinant of the performance of vertebrates and responds sensitively to a variety of internal and environmental factors. To understand physiological mechanisms underlying variations of fitness, we investigated effects of demanding conditions associated with certain life-history events, food availability, and population density on the oxygen delivery system in free-ranging edible dormice (Glis glis). We sampled blood (n = 248) and urine (n = 319), performed an erythrocyte haemogram and visually determined the presence of haemoglobinuria. Reproduction leads to increased mortality in edible dormice and our study now reveals severe haematological impairments during reproduction that were associated with nutrient and energy deficits and stress. These effects were even more pronounced in subsequent reproductive years, indicating prolonged physiological impairment. Under limited food availability, the rate of erythrocyte generation was reduced. This seems to be part of an energy saving strategy instead of representing a poor body condition as survival probability in this species is high in years of low food availability. A high prevalence ratio of haemoglobinuria (up to 85%) at the end of the active season indicated amplified erythrocyte destruction through haemolysis. This may be the result of a preparative mechanism to avoid massive oxidative damage during the long hibernation period. Most ecophysiological studies so far focus on single erythrocyte parameters on a short time scale, which could be misleading. Our results clearly highlight that a wide-array RBC approach is a powerful tool for investigating mechanisms underlying physiological performance and fitness, also for other vertebrate taxa.