In total, 20–24 subspecies have been described for Dryomys nitedula in the Palearctic region (Mohammadi et al. 2021). The need for systematic revisions of this species in the Western Palearctic is stressed (Holden-Musser et al. 2016, Mohammadi et al. 2021, Mammal Diversity Database 2022). Further, based on an analysis of mitochondrial and nuclear DNA, it has been reported that the Italian (D. n. aspromontis) and Iranian (D. n. pictus) subspecies may be distinct species. However, additional morphological and morphometric evidence, as well as genetic studies incorporating material from the entire range of D. nitedula, are needed before said taxa may be elevated to species status (Mohammadi et al. 2021).

European regional assessment: Least Concern (LC)
EU 27 regional assessment: Least Concern (LC)

This species has a wide but fragmented distribution. In some areas, it is considered stable, but in at least 11 of the 26 countries where this species occurs in Europe, this species has been included on national Red Lists or is considered to have an unfavourable conservation status. However, populations have not been quantified, and there is no evidence that any decline could be approaching the threshold for the population reduction criterion (30% in 10 years). Therefore, this species is assessed as Least Concern for both Europe and the EU 27 Member States. Population monitoring is required, particularly in countries where this species is of conservation concern.

The Forest Dormouse (Dryomys nitedula) has an unusual distribution extending from the Alps eastwards, with multiple isolated subpopulations occurring often in forested mountains (Kryštufek 1994, Holden-Musser et al. 2016). In Europe, this species occurs from Switzerland and north-eastern Italy (and an isolated population in the south Italy) in the west through eastern and southern Europe (including Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, Albania, Serbia, Macedonia, Greece, Bulgaria, and European Türkiye). Its range extends north to scattered populations in Lithuania and south-eastern Latvia, and east through central and southern European Russia to the Urals.

Outside of the European assessment region, its range extends through Anatolia (Türkiye) and the Caucasus to central Asia, reaching as far as 90°E. Many isolated populations occur on the edge of its range, including in Israel, central Iran, Afghanistan, the Tien Shan Mountains, northwest Xinjiang (China) and western Mongolia. Its vertical range is from sea level to 2,300 m (Kryštufek 1999, Holden-Musser et al. 2016).

In some southeastern areas of Europe (e.g. Bulgaria, Turkish Thrace, Moldova) it is locally common, reaching densities of 23-25 individuals per hectare in Moldova (Lozan et al. 1990, Kryštufek 1999). However, average densities are comparatively very low in Eastern Europe: 2.4 ind/ha in Mordovia (Andreychev 2021), and less than 1 ind/ha in Lithuania, Poland, and Ukraine (Holden-Musser et al. 2016). There is only one population remaining in Switzerland (Tester and Müller 2000), two in Lithuania, and one in Latvia (Juškaitis 2018). On the western border of its range, it is considered rare (Juškaitis 2018). Populations are likely to have declined due to deforestation (Rašomavičius 2021).

The Forest Dormouse occurs in a broad variety of habitats including broad-leaved, mixed, coniferous and dwarf montane woodland, shrub- and grassland, rocky areas, and wood-steppe. Presence of shrub layer and dense young trees in the understory are the main habitat requirements (Airapetyants 1983, Kryštufek 1999, Holden-Musser et al. 2016). Although it is indicated that the species is not found in human-dominated habitats such as agricultural areas (Batsaikhan et al. 2016), it is known to utilise forest shelter belts in agricultural regions (Markov et al. 2009). It can also live in human settlements located in the forest and enter houses (Andreychev 2021).

This species is omnivorous, with a diverse food spectrum including both plant foods, such as fruits and nuts, as well as animal foods, such as adult insects and their larvae, millipedes, birds and their eggs. The proportion of food of animal origin is higher in its diets in northern and western parts of the distribution (Airapetyants 1983, Juškaitis & Baltrūnaitė 2013, Holden-Musser et al. 2016). The Forest Dormouse has only one litter of young during the short activity season, and litters of four young are most frequent (range one to six) (Holden-Musser et al. 2016). The activity season lasts only about 4.5 months from late April through early September on the northern edge of its distribution, but up to eight months (April–November) in Bulgaria (Markov et al. 2009, Juškaitis 2015, Holden-Musser 2016). Hibernation nests are situated underground, often under tree roots (Holden-Musser et al. 2016).

Chemical use in rural areas may be a risk to this species, with one study reported the findings of considerable concentrations of highly toxic heavy metals in tissues of the Forest Dormouse (Markov et al. 2016). Forest felling in dormouse habitats is the main threat to this species in Lithuania (Rašomavičius 2021).

The species is not known to be utilised.

The species is protected by international law under the Bern Convention (Appendix III) and the EU Habitats and Species Directive (Annex IV), in parts of its range where these apply. It is found in a number of protected areas. According to an Assessment of Conservation Status under Article 17 of the Habitats Directive for the period 2013-2018, its conservation status is Favourable only in five countries (Bulgaria, Greece, Italy, Romania and Slovenia) out of 14 EU countries in which this species occurs.
The Forest Dormouse is included on national Red Lists in some European countries, mainly those situated at the periphery of its distribution (e.g. Germany, Latvia, Lithuania, Poland, Albania and Switzerland). As well as population- and threat-monitoring, this species would particularly benefit from further taxonomic research. The status of a number of its subspecies is unclear (Holden-Musser et al. 2016). Habitat management and restoration is recommended.