Ecological drivers of garden dormouse (Eliomys quercinus) occupancy in a human modified landscape in Germany
Data files
Feb 28, 2025 version files 42.36 KB
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occu-data.csv
32.45 KB
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README.md
9.91 KB
Abstract
The garden dormouse (Eliomys quercinus) is an understudied mammal species endemic to Europe. Once distributed widely across the continent, its eastern populations have significantly declined, with the species now found in only 50% of its former range. In Germany, it also occurs in spruce forests in low mountain ranges. However, this habitat has recently been lost due to bark beetle infestation following a prolonged period of drought. In some places, not only are the dead trees removed, but also all the branches and topsoil.
We assessed habitat requirements of a garden dormouse population in such a changing habitat in the Harz Mountains, Germany. To assess garden dormouse occupancy, we conducted transect surveys using footprint tunnels in July and October 2022 for the presence of garden dormice. Additionally, we measured covariates such as coverage of tree, shrub, and herb layers, as well as deadwood, soil characteristics, and reforestation. Using single-season occupancy modelling, we evaluated the effects of these habitat covariates on the occupancy of the garden dormouse.
Our results indicated that garden dormouse occupancy was negatively affected by herb cover, but positively associated with plant successional stages. Furthermore, occupancy of the garden dormouse was positively coupled with the occurrence of the hazel dormouse (Muscardinus avellanarius). Detection probability increased with higher weekly minimum temperatures.
For the conservation of garden dormice in low mountain ranges like the Harz, practical measures should include establishing interconnected forest edges and strips. Moreover, we suggest adopting a dynamic, mosaic approach to felling, avoiding topsoil removal, and promoting regeneration that fosters semi-open successional habitats as essential strategies.
https://doi.org/10.5061/dryad.6t1g1jx94
Description of the data and file structure
In July 2022, we installed 100 footprint tunnels across 10 transects positioned perpendicularly along a forest road in the western Harz Mountains to detect garden dormouse. Each transect, consisting of 10 footprint tunnels, was established every 200 m, with 5 tunnels on each side of the road. To analyse habitat preferences of the garden dormouse, we collected several environmental parameters at each footprint tunnel location.
Files and variables
File: occu-data.csv
Description: The data file includes all data collected in the field to analyse garden dormouse habitat preferences. Please note that delimiter is a semicolon (;), and the decimal separator is a comma (,).
Variables include:
- tunnel.ID (counts tunnel from 1 to 100),
- number of control days (control_days),
- elevation (m),
- longitude and latitude of the location of the tunnel.ID,
- presence-absence data of the occurrence of hazel dormouse in the footprint tunnel (hazel_dormouse),
- Soil surface exposure (soil.surface.exposure),
- presence-absence data of specific plants (Prunus avium, Sorbus nigra, Corylus avellana, Rubus fruticosus, Rubus idaeus, Vaccinum myrtillus),
- density, size, dispersion and abundance of tree stump, fallen log and dead wood (see table 1),
- tree dispersion and size of overstory (overstory.tree.size, oversoty.tree.dispersion) and understory (understory.tree.size, understory.tree.dipersion),
- number of tree species (N.woody.species),
- woody stem density of overstory and understory (woody.stem.density.overstory and woody.stem.density.understory),
- percentage of herb-, shrub- and tree-cover (canopy.closure, shrub.cover and herbaceous.cover)
and
- percentage of the soil surface exposure (soil.surface.exposure).
Data on detection (Det: presence/absence, 0/1) of garden dormouse, precipitation (Prec: mm), minimum temperature (Temp: °C) and Julian date (the day number within the year) were collected with a repetition of 12 on every footprint tunnel location. The columns are sequentially numbered according to the recording date: e.g. Det270722, Det030822, indicating the presence/absence data collected on the 27th of July 2022 and on the 3rd of August 2022.
Shrub diversity (shrub_diversity: defined as number of plant species), distance (m) to the forest trail from the footprint tunnel (Dist_Road) and Soil loss (soil_loss) were also collected on each tunnel.ID.
Furthermore, we divided the study area into the following five predominant habitat types (habitat): reforestation, forest strip, deforestation, succession and old-growth forest. The categories reforest (Tabl. 1), forest strip (forest_strip: presence/absence) and succession (Tabl. 1) were also listed in separate columns. The forest was further classified (tree_species) as beech (Fagus sylvatica), spruce (Picea abies), mixed and open areas (i.e., no trees while containing grasses and shrubs). The selection of covariates was based on Bertolino (2007) (Table 1). Vegetation layers were defined as in Table 2.
Table 1 Definition of the predictor variables measured on each footprint tunnel location in a 2.5 m radius.
| Predictor variable | Definition and units |
|---|---|
| Density | Average number of tree stump, fallen log, dead wood |
| Size | Average diameter (cm) of tree stump, fallen log |
| Dispersion | Average distance (cm) of tree stump, fallen log, dead wood |
| Abundance | Average total length (m) of fallen log |
| Diversity | Number of plant species (tree: N.woody.species, shrub: shrub_diversity) |
| Cover | % covered by stratum (canopy.closure, shrub.cover and herbaceous.cover) |
| Exposure | % not covered by any vegetation (soil.surface.exposure) |
| Reforestation (reforest) | 0: no reforestation; 15: reforestation younger than 15 years; 30: reforestation between 15-30 years; 45: reforestation between 30-45 years; 50: reforestation older than 45 years |
| Succession | 0: no natural succession (includes areas where succession has not started yet: bare soil, fresh clear cut; areas already reached climax: grown forest; areas with reforestation; 1: young or adjouning (characterised by herbaceous layer, first shrubs emerge); 2: intermediate (shrub layer begins to dominate herb layer; no trees); 3: mature (characterised by pronounced shrub layer and appearence of birches) |
| Soil loss | 0: no mechanical soil loss due to forest management |
| 1: mechanical soil loss due to forest management | |
| Hazel dormouse | 0: no detection of hazel dormouse; 1: detection of hazel dormouse |
Table 2 Definition of vegetation layers.
| Overstory | Woody vegetation ≥ 17.5 cm DBH |
|---|---|
| Understory | Woody vegetation > 2 m in height and < 17.5 cm DBH |
| Shrub level | Woody vegetation ≤ 2 m in height |
| Herb level | Herbaceous vegetation |