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European ground squirrel
European ground squirrel
European ground squirrel
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European ground squirrel
In Slovakia
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Sciuridae
Genus: Spermophilus
Species:
S. citellus
Binomial name
Spermophilus citellus
Geographic range
Synonyms

Citellus citellus (Linnaeus, 1766)
Mus citellus Linnaeus, 1766

The European ground squirrel (Spermophilus citellus), also known as the European souslik, is a species from the squirrel family, Sciuridae.[2] It is among the few European species in the genus Spermophilus. Like all squirrels, it is a member of the rodent order. It is to be found in eastern and central Europe from southern Ukraine, to Asia Minor, Austria, the Czech Republic, Slovakia, Serbia, Hungary, Greece, Romania, Moldova, Bulgaria, North Macedonia and north as far as Poland but the range is divided in two parts by the Carpathian Mountains.

The European ground squirrel grows to a length of approximately 20 cm (8 in) and a weight of approximately 300 grams (11 oz). It is a diurnal animal, living in colonies of individual burrows in pastures or grassy embankments. The squirrels emerge during the day to feed upon seeds, plant shoots and roots or flightless invertebrates. The colonies maintain sentinels who whistle at the sight of a predator, bringing the pack scurrying back to safety.

Breeding takes place in early summer when a single litter of five to eight young is born. The European ground squirrel hibernates between autumn and March, the length of time depending on the climate. In preparation they will build up reserves of brown fat during the late summer.

Description

[edit]

The European ground squirrel is about the size of a brown rat, with an adult measuring 20 to 23 cm (8 to 9 in) and a weight of 240 to 340 g (8.5 to 12.0 oz). It has a slender build with a short bushy tail. The short dense fur is yellowish-grey, tinged with red, with a few indistinct pale and dark spots on the back. The underside is pale with a sandy-coloured abdomen. The large dark eyes are placed high on the head and the small, rounded ears are hidden in the fur. The dental formula is 1.0.2.31.0.1.3. The legs are powerful with sharp claws well adapted for digging. Males are slightly larger than females otherwise they look alike.[3][4]

The European ground squirrel has a shrill alarm call that will cause all other individuals in the vicinity to dive for cover. It also makes various soft chirruping and growling noises.[3]

The European ground squirrel could be confused with the speckled ground squirrel which occurs in Poland (Lublin Voivodeship), Moldova, Russia, Belarus and Ukraine, but that species has dark brown fur spotted with white and a thin tail and lives in areas with coarser vegetation.[5]

Evolution and phylogeography

[edit]

The European ground squirrel is most closely related to the Anatolian ground squirrel and in particular to the Taurus ground squirrel. The earliest remains attributed to it come from the Yarımburgaz Cave and are about 226,000 years old. During the Pleistocene, the distribution of the European ground squirrel was limited to Southeastern Europe, mostly south of the Danube, as large parts of its current range in Central Europe were still inhabited by the closely related Spermophilus citelloides.[6] Only when S. citelloides became extinct during the early Holocene was the European ground squirrel able to expand its range into Central Europe, possibly favoured by the clearing of vegetation provided by neolithic farmers and their livestock.[7]

Distribution and habitat

[edit]

The European ground squirrel is native to central and southeastern Europe where its range is divided by the Carpathian Mountains. Its range includes land at altitudes of up to 2,593 metres (8,507 ft) in southern Ukraine, Asia Minor, Austria, the Czech Republic, Slovakia, Serbia, Hungary, Greece, Romania, Moldova, Bulgaria, North Macedonia and north as far as Poland.[1] It has become locally extinct in Germany and Poland but was reintroduced successfully into the wild in Poland in 2005. Some of the animals were sourced from the Budapest Ferenc Liszt International Airport.[8]

The European ground squirrel has very specific habitat requirements. It needs short turf in order to dig its tunnel system. It finds this on the steppes and in pasture, in dry banks, on sports fields, parks and lawns. These conditions are lost when changes in agricultural practice convert grassland into arable land and forest, or grazing ceases and the grass grows coarse and scrubland develops.[1] Other places with short vegetation that sometimes provides suitable habitat are railway embankments and road cuttings and verges.[3]

Behaviour

[edit]
European ground squirrel whistling
European ground squirrel eating the seeds of the denseflower mullein

The European ground squirrel is a colonial animal and is mainly diurnal. It excavates a branching system of tunnels up to 2 metres (6 ft 7 in) deep with several entrances. At other places in the home range it digs unbranched bolt holes in which to hide if danger threatens. If alarmed it emits a piercing whistle and when it is out in the open it often sits upright and looks around for predators. These include the least weasel, red fox, domestic cat and some species of birds of prey. It feeds on grasses, other plants, flowers, seeds, cultivated crops, insects and occasionally the eggs of ground nesting birds or their chicks.[3] A study in Bulgaria found that the squirrel spent about eleven hours a day outside its burrow in mid-summer but by early autumn this has reduced to seven hours. Rather over half of the day was spent foraging but other activities observed included exploration, running, sitting, grooming, digging, scent marking and vigilance.[9] During the winter it stops up the entrances to its burrow and hibernates in a nest of dry vegetation. Each individual occupies a separate chamber and during this period, the body temperature drops to 2.0 °C (36 °F), and the heart rate slows to a few beats per minute. During hibernation, the squirrel may wake up briefly for a few days and uses up the fat reserves accumulated during the summer, consuming about 90% of the fat stored in the body.[10] In Bulgaria hibernation lasts from September to March.[9]

Breeding

[edit]

After emerging from hibernation in the spring, mating takes place during April or May. The gestation period is about twenty six days and five to eight young are born in a chamber deep in the burrow. They are naked and blind and their eyes open at about 4 weeks old. The female feeds them for six weeks and soon after that they are ready to leave the burrow. They reach maturity the following spring and may live for eight to ten years.[3]

Status

[edit]

The European ground squirrel is listed as being endangered by the IUCN in its Red List of Threatened Species. This is because the population trend is downward and it is believed that, over the last ten years[when?], the population has diminished by more than 30%. The southern and the northwestern and northern parts of the range are most seriously affected. The main threats are the conversion of grassland and pasture to cultivated fields or to forestry, and the abandonment of grassland and its reversion to unsuitable tall grass meadows and bushy habitats that do not suit the animal. Urbanization and road building have sometimes fragmented communities and prevented recolonisation of empty sites.[1]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

European ground squirrel

View on Grokipedia
from Grokipedia
The European ground squirrel (Spermophilus citellus) is a medium-sized, colonial belonging to the Sciuridae, endemic to the open grasslands of central and southeastern , where it inhabits short-vegetation habitats such as steppes, pastures, and meadows from to elevations of 2,500 m. This diurnal species is characterized by a robust, rounded body, short tail (20–40% of head-body length), and small, rounded ears; adults typically measure 174–228 mm in head-body length and weigh 125–380 g, with pelage that is cream-buff to yellowish and marked by black vermiculations. Primarily herbivorous, it feeds on green vegetation, seeds, roots, and occasionally arthropods, while exhibiting behaviors such as burrowing for , reproduction, and refuge, with females producing a single annual litter of 2–11 young after a 25–29-day period. The species' range spans disjunct populations across countries including the , , , , , , , , , and , between approximately 40°20'N–51°00'N and 12°40'E–29°00'E, though it has become historically extinct in areas like , , and , with successful reintroduction efforts establishing populations in and ongoing programs in other regions. It prefers arid lowlands with sandy loam-loess soils and avoids plowed fields or tall-grass areas, relying on anthropogenic management of grasslands for persistence, as natural habitats have been altered by and . Socially, S. citellus lives in colonies with complex burrow systems, emerging from in March–April for mating and foraging, and it plays an ecological role in and soil aeration within its ecosystems. Currently classified as Endangered on the (as of 2024) due to ongoing population declines exceeding 50% in fragmented , driven by agricultural intensification, loss, abandonment, development, and climate change impacts. Conservation measures include protection under the (Annexes II and IV) and the Bern Convention (Appendix II), alongside active reintroduction programs and restoration in countries like Czechia and ; recent translocations as of 2025 have bolstered populations, such as increasing numbers in to over 36,000 individuals.

Taxonomy and physical characteristics

Taxonomy

The European ground squirrel (Spermophilus citellus) is a species of in the family Sciuridae, classified under the order Rodentia and suborder Sciuromorpha. Its full taxonomic hierarchy is as follows: Kingdom Animalia, Chordata, Class Mammalia, Order Rodentia, Suborder Sciuromorpha, Family Sciuridae, Subfamily , Tribe Marmotini, Genus , and Species S. citellus. This genus encompasses Eurasian ground squirrels, with S. citellus being one of the few representatives native to . The species was first described by Carl Linnaeus in 1766 under the name Mus citellus, with the type locality restricted to Wagram, Austria. Synonyms include Mus citillus (Pallas, 1779) and Citellus citellus (Linnaeus, 1766), reflecting historical shifts in generic nomenclature from Mus to Citellus before settling on Spermophilus. The name Spermophilus derives from Greek roots meaning "seed-loving," alluding to the squirrel's foraging habits, while citellus is a diminutive form of Latin citelus, possibly referencing a small weasel-like creature. Up to eight subspecies have been proposed based on variations in pelage color, body size, and cranial morphology across its range, including S. c. gradojevici (Martino and Martino, 1929), S. c. istricus (Calinescu, 1934), S. c. martinoi (Peshev, 1955), and S. c. balcanicus (Markov, 1957). However, these distinctions lack clear genetic or morphological discontinuities, leading some researchers to consider S. citellus monotypic pending further phylogenetic analysis. Molecular studies support its placement within the Spermophilus clade, distinct from North American ground squirrels reclassified into genera like Urocitellus.

Physical description

The European ground squirrel (Spermophilus citellus) is a medium-sized characterized by a compact, rounded body, short legs, and a that measures 20–40% of the head and body length. Adults typically have a head and body length of 174–228 mm, with males averaging slightly larger at 176–228 mm and females at 174–217 mm. Tail length ranges from 31–90 mm in males and 38–75 mm in females, while hind foot length is 30–43 mm. Body mass varies seasonally and by sex, with males weighing 125–380 g and females 131–353 g, though individuals can exceed 450 g in late summer. The pelage is short and dense, providing in grassy habitats. The dorsal fur is cream-buff to yellowish, vermiculated with black for an overall grizzled appearance, often with obscure light mottling and indistinct pale or dark spots. The ventral surface is buff to pale yellow, sometimes more saturated than the sides, while the has a grizzled upper surface, dull buff underside, and dark tip. A lighter morph occurs in some populations, featuring white and belly along with white blotches on the head and dorsum. The ears are small, rounded, and densely haired without tufts, and the eyes are large (approximately 8 mm in ) with wide placement and a faint whitish or yellowish eye-ring. Sexual dimorphism is minimal, with males and females similar in pelage coloration and overall proportions, though males tend to be larger in linear measurements and mass. Juveniles are born with hair and reach an average mass of 61.4 g by 30 days old, developing adult-like coloration by weaning. The dental formula is I 1/1, C 0/0, P 2/1, M 3/3 = 22, adapted for a herbivorous diet, and the paws feature yellowish fur, four naked pads, and claws up to 8 mm long for digging.

Evolutionary history and distribution

Evolution and phylogeography

The European ground squirrel (Spermophilus citellus) belongs to the genus Spermophilus within the subfamily Marmotinae, which originated through a rapid diversification of ground squirrels approximately 10–14 million years ago (Miocene), coinciding with the expansion of grasslands in western North America and Eurasia. The genus Spermophilus is paraphyletic relative to marmots (Marmota) and prairie dogs (Cynomys), with Eurasian lineages diverging from North American relatives during this period, likely driven by climatic warming and habitat shifts. Fossil evidence indicates that early Spermophilus species, such as S. praecox (the oldest known, from the late Pliocene ~2.6 million years ago in southeastern Europe), represent immigrants possibly derived from an Otospermophilus-like ancestor, marking the initial colonization of Eurasia. This species persisted until ~1.7 million years ago, evolving gradually into S. nogaici around 1.6 million years ago (early Pleistocene), which exhibits dental and cranial traits ancestral to modern S. citellus, including high-crowned teeth and reduced posterior lobes. During the Pleistocene, S. citellus adapted to steppic environments amid glacial-interglacial cycles, with its distribution initially confined to southeastern Europe south of the Carpathians and . Mitochondrial DNA analyses reveal three historically isolated lineages: a northern widespread across , a southern persisting in refugia such as Turkish , , Macedonia, and the , and a distinct Jakupica lineage isolated on Mount Jakupica in Macedonia. These lineages diverged approximately 0.58 million years ago, with the northern and Jakupica splits occurring ~0.30 million years ago, reflecting isolation in southern Balkan refugia during glacial maxima that preserved steppic taxa. The Balkan Peninsula served as a major Pleistocene refugium, harboring high genetic diversity, particularly in southeastern and European Turkey, where diversity reaches 0.0034–0.0047, compared to lower values (0.0007–0.0016) in peripheral populations. Post-glacial expansion during the facilitated northward recolonization into and southward into , following the spread of open grasslands, with founder populations likely originating in the Upper Thracian Valley before 0.23 million years ago. This process aligns with the centre-periphery hypothesis, showing decreased toward range margins and no clear latitudinal gradient within the , as evidenced by haplotype diversity of 0.383 in Greek populations and 0.529 in Serbian ones. In , the ancestral range, two main lineages (northern Danubian and southern Thracian) separated ~10,000 years ago, separated by the Stara Planina Mountains as a barrier, with overall heterozygosity ranging from 0.55 to 0.78 and strong population differentiation (mean F_ST = 0.184). Admixture occurs in transitional areas, underscoring ongoing amid . These patterns highlight the species' evolutionary resilience in continental climates but vulnerability to recent anthropogenic pressures.

Geographic distribution

The European ground squirrel (Spermophilus citellus) is endemic to central and southeastern Europe, with an extent of occurrence estimated at approximately 1,000,000 km². Its range spans latitudes from 40°20'N to 51°00'N and longitudes from 12°40'E to 29°00'E. The species occurs in Austria, Bulgaria, Czechia, Greece, Hungary, Moldova, North Macedonia, Poland (reintroduced), Romania, Serbia, Slovakia, Türkiye (European part), and Ukraine. The distribution is highly fragmented, consisting of two main disjunct portions separated by the and the (Djerdap) Canyon along the River. The northwestern portion includes the , , , , northern (north of the and rivers), (reintroduced populations), and western . The southeastern portion encompasses eastern , , northern , , Turkish (European ), southern and eastern , , and . This fragmentation has intensified due to ongoing habitat loss and isolation of populations. It has been extirpated from and . The species inhabits elevations from up to 2,500 m, primarily in open grasslands and steppes. In , the species was historically widespread, occupying about 94% of the country's territory until the mid-, but its current range is severely contracted, with ongoing population declines reported through the . At its southern distributional limit in , populations persist in three sub-regions: (including the Axios River valley and Mount Vermio), , and (Evros River delta), comprising 107 known colonies, of which only 37% were active during surveys from 2019 to 2021. These Greek populations have experienced a 62.4% reduction in overall range and 74.6% loss of colonies since the late , largely due to agricultural intensification and . In , translocations have supported populations across various sites, including mountainous areas up to mid-altitudes, highlighting efforts to maintain connectivity in the southeastern range.

Habitat

The European ground squirrel (Spermophilus citellus) primarily inhabits open, dry grasslands across central and southeastern , including short-grass steppes, pastures, and meadows, often with sparse shrubs or trees. These environments provide the necessary for predator detection and , with the favoring areas maintained by natural or human-induced disturbances like grazing or mowing to keep vegetation short. It avoids dense, tall-grass meadows and plowed arable fields, which limit construction and increase predation risk. Soil characteristics are critical for burrowing, with preferences for deep, well-drained types such as sandy loam-loess humus or alluvial-meadow soils in arid lowlands; the species shuns waterlogged, stony, or compacted substrates that hinder excavation. Associated vegetation includes drought-tolerant grasses like Andropogon ischaemum and Festuca pseudovina, supporting its herbivorous diet while maintaining open sightlines—optimal vegetation height is typically under 10–15 cm, where population densities can reach 15–19 individuals per on suitable slopes. In terms of , colonies often occupy south- or east-facing slopes with gradients exceeding 12°, and annual below 636 mm, conditions that enhance drainage and reduce humidity. The species occupies a broad elevational range from to 2,500 m, though densities are highest below 300 m in lowland steppes; at higher altitudes, suitable habitats become patchier. It tolerates some modified landscapes, including field margins, embankments, and semi-urban grasslands like sports fields or airport verges, but population declines occur with increasing , , and conversion to intensive or . In its southernmost range, such as , over 80% of individuals persist in agricultural mosaics or artificial open areas, highlighting adaptability but underscoring vulnerability to land-use intensification.

Behavior

Activity patterns

The European ground squirrel (Spermophilus citellus) is strictly diurnal, emerging from its burrow approximately 3.9 hours after dawn and retreating about 3.2 hours before dusk, resulting in an average aboveground activity period of 8.8 hours centered around midday.782<0001:SCRSAI>2.0.CO;2) During this time, individuals spend roughly 74% of their aboveground period , with the remainder devoted to vigilance, grooming, and social interactions. Activity exhibits a bimodal pattern, peaking in the morning and late afternoon, with a midday rest phase often observed under high ambient temperatures, particularly on sunny days when dark-furred individuals reduce visibility to avoid heat stress. Seasonal activity is tightly linked to reproductive cycles and environmental cues. Males typically emerge from hibernation in early March (around 9 March on average in ), followed by females about two weeks later (around 22 March), with emergence dates varying by latitude and warmer conditions prompting earlier activity. The active season spans from late winter to late summer, with males remaining aboveground longer during the period (up to early April) and pre-hibernation fattening (until early August), while females focus on , , and post-weaning care, concluding activity by late July. Photoperiod, rainfall, and reproductive status further modulate patterns; for instance, lactating females increase foraging time, and rain can suppress overall activity. As hibernators, European ground squirrels enter in late summer (females by 21 July, males by 6 August in southern populations), remaining underground for 5–7 months depending on sex and location—females typically longer (up to 228 days) than males (around 185 days).782<0001:SCRSAI>2.0.CO;2) During , they experience periodic euthermic arousals amid bouts of deep where body temperature drops below 0°C, aiding in arid or food-scarce environments; daily bouts also occur outside to manage metabolic demands.782<0001:SCRSAI>2.0.CO;2) In summer, activity declines under hot, dry conditions, with individuals becoming more lethargic and burrow-bound to mitigate desiccation.782<0001:SCRSAI>2.0.CO;2)

Social behavior

The European ground squirrel (Spermophilus citellus) exhibits colonial living in loosely structured groups where individuals maintain overlapping home ranges but occupy separate burrow systems as adults, beyond the maternal care period. This arrangement reflects a relatively asocial within the colony, with densities ranging from 18 to 48 individuals per in optimal habitats. Home ranges typically measure 0.1–0.4 ha, though adult males may expand to 1 ha, and there are no distinct territorial boundaries during mating; instead, focal areas are used communally by multiple individuals. Social interactions are limited and primarily nonaggressive outside the breeding season, increasing notably between males and females in the weeks preceding as proximity and tolerance grow, before declining post-. During the period, is directed mainly by males toward other males, accounting for 80.4% of observed aggressive acts such as chases and fights, while female toward males decreases to facilitate pairing. No instances of have been recorded, and juveniles disperse to independent burrows shortly after , reducing familial interactions. Scent marking by males occurs predominantly during the season to signal reproductive status. Communication among colony members relies heavily on vocalizations for predator detection and coordination. The species produces eight distinct call types, categorized into three tonal (including alarm calls) and five wideband variants (such as grunts). Alarm calls are short tonal sounds lasting 65–152 ms, featuring two harmonically structured elements with peak frequencies of 7,230–14,550 Hz, and serve to alert others to threats; emission peaks in coinciding with litter emergence from burrows. These calls exhibit individual signatures, aiding in kin or neighbor recognition within the , though explicit kin discrimination mechanisms remain undemonstrated in this .

Diet and foraging

The European ground squirrel (Spermophilus citellus) is primarily herbivorous, with its diet consisting mainly of green plant parts such as leaves, stems, flowers, seeds, and roots from grasses, forbs, and legumes. Common food plants include species from genera like Achillea (e.g., A. millefolium), Medicago, Trifolium, Poa, Cynodon, Carex, Plantago, and Salvia, with forbs comprising about 70% of the diet and grasses around 25%. Although predominantly plant-based, the species occasionally consumes invertebrates (e.g., beetles and caterpillars, up to 25% monthly in some populations), small vertebrates like lizards, bird eggs, and even small mammals such as common voles when available. Foraging occurs above ground during the active season ( to ), with individuals selectively harvesting vegetation based on rather than random availability, as indicated by low dietary similarity to surrounding plant communities ( 0.151–0.469). Rhizomes and tubers, such as those from and , are preferred and require excavation, taking up to 73.5 seconds per handling bout, while leaves and stems are consumed more quickly. In anthropogenic habitats, the diet shifts opportunistically toward abundant crops or weeds, but selective pressure favors nutrient-rich parts like rhizomes (38.9% of diet) over seeds (despite their prevalence in some seasons). Seasonal changes in diet reflect vegetation and energy needs: early spring (March–April) emphasizes seeds and stems for post- recovery; mid-season (May–July) features high plant diversity (up to 44 taxa, with and forbs dominant); late summer to autumn (August–October) focuses on , leaves, and increased or seeds to build fat reserves (35–40% body mass) for . Across 3,616 observed feeding bouts in , consumption peaked at 54.66% in May–June and 50.20% in September–October, underscoring their role in sustaining the short active period. Evidence suggests limited food storing behavior, primarily in summer for immediate use rather than survival, with caches of tubers (e.g., 290–380 g of L. tuberosus) buried in blind-ending tunnels at depths of 30–90 cm to evade predators. This caching is not universal but occurs in resource-abundant areas, complementing daily that totals dozens of taxa per site (average 32.5 per fecal sample analyzed).

Reproduction

Breeding biology

The European ground squirrel (Spermophilus citellus) breeds once annually, with mating occurring shortly after emergence from . Females typically emerge in late to early , followed closely by receptive periods lasting 1–3 days per individual, resulting in a concentrated breeding window from late to mid-. Adult males emerge approximately 14–19 days (average 15.5 days) earlier than females, undergoing full gonadal maturation prior to emergence, while yearling males often delay maturation and emerge with females. The is characterized by , where males increase ranging, scent-marking, and agonistic interactions to locate and monopolize multiple females, though each female usually copulates with only a single male in her . Gestation lasts 25–29 days, averaging 29 days in field conditions, after which females give birth underground in natal burrows. Litter sizes range from 2 to 11 young, with averages of 5.4 for females and 6.8 for older multiparous females; litter size correlates positively with maternal age and body mass at emergence. Newborns weigh approximately 5–6 g, are altricial, and remain in the natal burrow for 22–61 days of , depending on litter size and resource availability. is influenced by female body condition, with heavier females at emergence more likely to conceive and produce larger litters. Parental investment is primarily maternal, with females provisioning and defending the , but males contribute paternal effort by excavating and maintaining litter for their copulatory partners' , which enhances juvenile mass at emergence. This male assistance trades off against mating effort, as high-mating-success males invest less in post-copulatory care, leading to body mass losses of up to 20% during the breeding period due to reduced . is reached by females after their first and by males as yearlings or in their second year, contingent on body condition.

Development of young

Newborn European ground squirrels ( citellus) are altricial, born blind and hairless after a period of 25–29 days, with an average of 5.25 g. begins to appear between 15 and 17 days of age, eyes open at 22–25 days, and upper and lower incisors erupt between 25 and 27 days postpartum. Juveniles first emerge from the natal burrow at approximately 25 days of age, coinciding with the onset of aboveground activity. Postnatal growth is rapid initially, with juveniles reaching a mean body mass of 61.4 g by 30 days of age. occurs between 49 and 56 days, varying with litter size, after which young rely increasingly on solid food. Structural somatic growth ceases around 57 days, shifting energy allocation toward fat accumulation for . Following emergence, juveniles remain near the natal burrow for several weeks, learning and vigilance behaviors from the mother. Natal dispersal typically begins 30–40 days after and can extend up to 350 m, primarily driven by males to reduce and competition. Juveniles enter from August to October, lasting about 191 days, emerging the following spring. Females generally reach after their first , while males exhibit facultative maturity, with some reproducing as yearlings and others delaying until their second year.

Conservation status

The European ground squirrel (Spermophilus citellus) is classified as Endangered on the , with a decreasing population trend observed across its range in Central and Southeastern . This decline has been attributed to habitat loss and fragmentation, leading to an estimated overall reduction exceeding 50% over the past three generations (approximately 18–24 years). Population estimates vary widely, but the species' total numbers are thought to have dropped from millions in the mid-20th century to fragmented colonies totaling in the tens or hundreds of thousands today, with ongoing monitoring revealing persistent downward trajectories in most areas. In Slovakia, populations experienced a drastic 99% decline over the past 50 years, reducing from millions to around 20,000 individuals by 2020, rendering the species critically endangered at the national level. However, conservation efforts have increased the population to approximately 36,000 by 2023, with over 1,000 additional translocations in 2025. Similarly, in Hungary, colony numbers sharply decreased from the mid-20th century, with a pronounced decline from 1964 to 2012, dropping to an estimated 190 active colonies by 2010; however, conservation interventions since 2012 have stabilized the trend, though forecasts suggest potential further reductions if efforts lapse. In Greece, at the southern edge of its range, the distribution has contracted by 62.4% (from 125 to 31 grid cells) and colony numbers by 74.6% (from 119 to 31 localities) between historical records and 2019–2020 surveys, with current populations totaling only about 378 individuals across 31 sites, averaging 7.4 individuals per hectare. Regional variations highlight the species' vulnerability, with reporting 30% of known colonies extinct and only 42% of remaining sites viable, contributing to a national critically endangered status. In the , populations fell to approximately 6,500 by 2020, reflecting a broader pattern of fragmentation and isolation in agricultural landscapes, though ongoing reintroduction efforts, including 115 releases in 2025, have contributed to recovery. While some localized reintroduction efforts have shown temporary increases, such as a 21% rise in Hungarian colonies post-2012, the overall continental trend remains negative, with genetic studies indicating reduced diversity in isolated populations that exacerbates decline risks.

Threats

The primary threats to the European ground squirrel (Spermophilus citellus) stem from habitat loss, degradation, and fragmentation, which have driven a suspected of over 50% in the past and are projected to continue into the future. These impacts are largely anthropogenic, affecting the species' preferred open grasslands and steppes across its range in . Agricultural intensification represents a major driver, involving the conversion of grasslands to , , and excessive mowing that eliminate suitable short-grass habitats essential for and burrowing. In member states, this process continues to reduce quality and extent, with examples including grassland destruction in , , and . Conversely, the abandonment of traditional pastoral practices in some regions leads to habitat succession into tall-grass or shrub-dominated areas unsuitable for the species, further fragmenting populations. Pesticide and use exacerbates these issues by directly poisoning individuals and reducing invertebrate prey availability, particularly in agricultural landscapes where the squirrels reside. Historical large-scale programs, dating back to the , targeted the species as an agricultural nuisance, contributing to severe population reductions across much of its range. development, including roads, urban expansion, and projects such as wind farms, causes direct and increases mortality through vehicle collisions and barriers to dispersal. For instance, proposed wind power installations in threaten key colonies on Mount Vermio. Illegal activities like unauthorized ploughing in , , , and also destroy burrows and feeding grounds. Flooding events, potentially linked to , pose additional risks by inundating low-lying habitats. While natural predation by species such as and mustelids affects juveniles more severely, habitat fragmentation amplifies these risks by isolating colonies and limiting escape options. Translocation efforts for conservation carry secondary threats, including the potential introduction of parasites or diseases, though these are managed through protocols. Overall, the species' dependence on human-maintained open habitats underscores the need for targeted land management to mitigate these pressures.

Conservation measures

The European ground squirrel (Spermophilus citellus) is protected under international and regional legal frameworks to address its Endangered status. It is listed in Appendix II of the Bern Convention, requiring strict protection and habitat conservation measures across signatory states. Within the , it is afforded protection under Annexes II and IV of the (Council Directive 92/43/EEC), mandating the designation of Special Areas of Conservation and prohibiting deliberate capture or disturbance. Additionally, over 400 sites have been established specifically for its conservation, focusing on key habitats in . Habitat management forms a of conservation efforts, emphasizing the maintenance of open grasslands essential for the species' burrowing and needs. Regular activities such as mowing, by , and removal of encroaching shrubs and trees are implemented to prevent overgrowth, ideally keeping grass heights below 15 cm during the active season. These measures counteract agricultural intensification and succession to scrubland, which fragment suitable s. In countries like and the , such management is integrated into national action plans and EU-funded projects, often within protected areas, to sustain viable populations. For instance, maintenance has been prioritized following Bulgaria's EU accession to align with habitat directive requirements. Reintroduction and translocation programs have been widely adopted to bolster declining or extirpated populations, particularly in western parts of the range. Successful reintroductions occurred in Poland starting in 2005 and in , where captive-bred individuals were released into restored sites. In , translocations along altitudinal gradients, such as in Vrachanska Planina, employ techniques like artificial burrows with retention caps to improve survival rates and establishment. These efforts, supported by NGOs like Green Balkans and government agencies, follow methodological guidelines and have reinforced colonies in areas like Sinite Kamani . Site preparation, including manipulation for burrowing, has proven critical for long-term success. In , translocations have contributed to population growth from 20,000 in 2020 to over 36,000 by 2023, with more than 1,000 individuals moved in 2025 alone. Ongoing monitoring and research underpin these initiatives, with EU action plans calling for population assessments, threat evaluations, and habitat suitability studies to inform . Ex situ conservation, including and housing protocols, complements efforts by providing a safeguard against local extinctions, as seen in species protection programs in . Collaborative projects, such as those under the LIFE Nature program, integrate these elements to enhance connectivity between fragmented populations and mitigate broader threats like .

References

  1. https://cales.arizona.edu/research/redsquirrel/res_pdf/Mamm%20Spec%20Spermophilus%20citellus%2014.pdf
  2. https://pmc.ncbi.nlm.nih.gov/articles/PMC12024762/
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