1. IntroductionThe Grey hamster (Cricetulus migratorius Pallas, 1773) is distributed from the Balkans to China and Mongolia (Kryštufek et al., 2008). It can utilise various habitats – steppes, semideserts, and even the surroundings of human settlements – and can go up to 4300 m above sea level (Gromov and Erbajeva, 1995). This is one of the three hamster species that occur in Europe (Mitchell-Jones et al., 1999). For all of them significant changes and decreases in their ranges have been observed, mainly due to agroenvironmental practices (e.g., changes in habitat utilisation, use of pesticides) or collection for the pelt (Cricetus cricetus) (Nechay, 2000).
During the Pleistocene, the Grey hamster was widespread throughout Europe and reached Spain and Great Britain [sensu Kowalski (2001); the author joined under this name besides Cricetulus migratorius a small fossil form Allocricetulus bursae, but see Hír (1993) and Cuenca-Bescós (2003) for further comments about the status of these forms]. In the beginning of the Holocene the species still inhabited Slovenia (Toškan and Kryštufek, 2009). In spite of its extensive range, data about its morphology and variation are scarce (Pradel, 1981; Doğramacı, 1989; Hír, 1993).The cricetids are amongst the most poorly studied rodents in the Palaearctic; thus, studying their morphology and the variation of the species will provide key information about the group’s evolution and its origin.
In Bulgaria the Grey hamster was first discovered in 1959 (Peshev et al., 1960). Only single findings were reported afterwards, mainly from south-eastern Bulgaria, reported in regional journals (in Bulgarian: Straka, 1962; Markov, 1964; Simeonov, 1964a, 1964b). Here I summarise the distribution and the species’ status in Bulgaria, and present new data about the species’ morphology from the western part of its range.
2. Materials and methodsThis research is based on collected material from pellets and food remains from different birds of prey and owls that I obtained between 2001 and 2014 from various parts of Bulgaria. I identified and analysed a total of 27,449 individual small mammals found at roosts and nests from eastern and south-eastern Bulgaria of the following species: Barn owl (Tyto alba), 20,157 small mammals; Tawny owl (Strix aluco), 472; Little owl (Athene noctua), 1861; Long-eared owl (Asio otus), 2709; Long-legged buzzard (Buteo rufinus), 643; and Eastern imperial eagle (Aquila heliaca), 1607. Some preliminary data about new findings of C. migratorius in Bulgaria have already been presented (Nedyalkov, 2013).
For morphological comparison I used 6 complete specimens of the Grey hamster collected from Central Kazakhstan (46°23′30″N, 74°01′44″E) and 8 mandibles found in the diet of Barn owl and Long-legged buzzard from Central Anatolia, Turkey (37°19′14″N, 33°11′13″E).
Abstract: During the last decade I collected extensive new information about the distribution of the Grey hamster (Cricetulus migratorius) in Bulgaria, mainly through the study of pellets of birds of prey and owls. New data about the dental morphology and morphometrics, distribution, and current status of the Grey hamster in Bulgaria are presented. The Grey hamster has been found in the diet of the Barn owl (Tyto alba), Little owl (Athene noctua), and Eastern imperial eagle (Aquila heliaca). It contributed a negligible part of the studied pellets: only 0.06% of individuals from 27,449 small mammals. The presence of the species was confirmed only in south-eastern Bulgaria, while in northern Bulgaria the species went extinct. The species’ distribution in the Balkans is discussed.
Key words: Grey hamster, morphology, birds of prey, owls, distribution
Received: 01.08.2015 Accepted/Published Online: 05.01.2016 Final Version: 06.12.2016
Research Article
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The measurements of teeth are made in accordance with the methodology described by Pradel (1981), while the terminology used follows Hír (1989). The teeth measurements were taken by stereomicroscope (accuracy: 0.05 mm), and molar row – coronal length, with а digital caliper (accuracy 0.01 mm). The abbreviations of the characteristics are as follows: M/m – upper and lower molar, L – greatest length, W – greatest width, MNI – minimum number of individuals, identified by the maximum count identified fragments from the left and right mandibula, the maxilla, or separate teeth.
3. Results 3.1. Data from the diet of the avian predatorsFrom the analysed 27,449 individual small mammals from pellets and prey remains, a minimum of 17 specimens of the Grey hamster were found as part of the diet of three avian species: Barn owl (Tyto alba), Little owl (Athene noctua), and Eastern imperial eagle (Aquila heliaca). It was not found in the diets of the other 3 studied species.
The Grey hamster was represented in different proportions in the diets of the avian predators (Table 1). Altogether, it constitutes a negligible part from the
birds’ diet: 0.06% of the analysed material (27,449 small mammals).
The Grey hamsters were identified mainly by their cranial and mandibular bones. The most complete remains were found in the remains of the Barn owl (Figure 1). One of the strongest bones, the mandible, remained entirely complete in the Barn owl pellets, in contrast to those from the Little owl and the Eastern imperial eagle, where it is fragmented in different degrees: broken proc. coronoideus, proc. articularis, and proc. angularis (Figure 1). This is due to differences in the feeding biology and habits of these species: the Barn owl swallows its prey (small mammals) whole, while birds of prey (eagles, buzzards, falcons) tear their prey to pieces (even small mammals) prior to swallowing, as do some small owl species (such as Little owl and Scops owl) for which insects are the main food (Marti et al., 2007).3.2. Morphological description data of the teethData from the dental measurements of the Grey hamster are presented in Table 2.
М1. The anterocone is usually deeply split into two cusps. The anterior connection between the paracone and protocone is present or poorly developed, but sometimes
Table 1. Cricetulus migratorius localities and proportion in the diet of the owls and the Eastern imperial eagle.
Predator Location Collection day C. migratorius (MNI) All small mammals
Tyto alba Matochina 20.8.2008 1 50
Tyto alba Levka 03.5.2006 14 532
Athene noctua Raykova mogila 10.8.2012 1 11
Aquila heliaca Sliven 15.3.2008 1 7
Figure 1. Degree of fragmentation of Cricetulus migratorius mandibles found in the diets of different avian predators; from left to right: A. heliaca, A. noctua, and T. alba.
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it may be absent between the paracone. Usually there is a parastyle (morphotype C in Hír, 1993), but sometimes with preanterocone cingulum (morphotype A), or both of them may be absent (morphotype D). These morphotypes were observed in the following frequencies: morphotype A, 20%; morphotype C, 40%; and morphotype D, 40% (n = 20 teeth). Only an anterostyle was not observed (morphotype B). The teeth are four-rooted.
M2. Anterior cingulum is well developed, especially on the labial side. Mesolophe is absent. Four-rooted tooth.
M3. The protocone is well developed; hypocone and metacone are strongly reduced. The anterolingual cingulum is less pronounced or may be absent.
m1. The anteroconide is divided by a depression into a lingual cusp and a labial cusp, which are of similar size. Preanteroconide cingulum is absent.
m2. All the four primary cusps are well developed. The mesolophid is also absent in this element.
m3. Mesolophid may or may not be present. There are a few teeth with little worn surface.
All lower molars have two roots.3.3. Distribution in BulgariaBased on this study and previous published data, the Grey hamster is found in 15 locations, mainly in south-eastern Bulgaria (Markov, 1960; Peshev et al., 1960; Straka, 1962; Markov, 1964; Simeonov, 1964a, 1964b; Georgiev, 2004; Milchev, 2009; Figure 2). Only one location is north of
Stara Planina Mountain (the main mountain ridge that separates the country into north and south) (Straka, 1962).
The species’ distribution is presented in two periods. The first one covers the time from the first finding of the species in Bulgaria until 1985, when all information about the species’ distribution was summarised in the first edition of Red Data Book of Bulgaria (Christov, 1985).
Between 1964 and 2003 there was no record of the species in Bulgaria, but this was due to a lack of systematic research in the south-eastern part of Bulgaria. Data about the species’ distribution after 2003 come from the study of diets of different owl species (Georgiev, 2004; Milchev, 2009).
My research confirmed the presence of the species in two old locations, around Sliven town (Simeonov, 1964a, 1964b) and Levka village (Peshev et al., 1960); and one more recent location, Rajkova mogila village (Georgiev, 2004).3.4. Habitat descriptionThe Grey hamster inhabits the lower and open part of south-eastern Bulgaria, where the climatic conditions are mild, with a Mediterranean influence penetrating through the Maritsa valley (Gruev and Kuzmanov, 1999).
The vegetation composition is dominated primarily by two habitats. The open land is cover by “Semi-natural dry grasslands and scrubland facies on calcareous substrates (Festuco-Brometalia)” (HD 92/43: 6210). The xerothermic
Table 2. Dental measurement (in mm) of Cricetulus migratorius from Bulgaria.
Meas. N Mean Min Max SD
LM1 31 1.58 1.4 1.7 0.071
WM1 31 1.07 0.95 1.2 0.055
LM2 29 1.18 1 1.3 0.091
WM2 29 0.96 0.85 1.05 0.051
LM3 27 0.93 0.85 1 0.054
WM3 27 0.90 0.8 1 0.055
LM1-3 27 3.70 3.55 3.91 0.104
Lm1 24 1.53 1.4 1.65 0.072
Wm1 24 1.01 0.9 1.1 0.040
Lm2 25 1.25 1.1 1.35 0.048
Wm2 25 1.04 1 1.1 0.031
Lm3 22 1.07 1 1.2 0.047
Wm3 22 0.98 0.85 1.05 0.057
m1-3 20 3.85 3.45 4.02 0.140
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meadows and pastures are covered by perennial grasses such as Chrysopogon gryllus, Bothriochloa ischaemum, and Festuca valesiaca, with some semishrubs and shrubs, mainly Paliurus spina-christi. Some authors determine this habitat as secondary steppe (Bondev, 1991). The second type is “Pannonian-Balkanic turkey oak-sessile oak forests” (HD 92/43: 91M0), where there are xerothermic and mesothermic oak forests with diverse floristic structure, usually dominated by Quercus frainetto (Bondev, 1991).
The Grey hamster was found to inhabit areas from 40 m up to 400 m a.s.l. (median: 200 m a.s.l.) in Bulgaria. Characteristic accompanying small mammal fauna found in the diets of different owl and birds of prey species is dominated by species inhabiting open habitats such as the White-toothed shrew (Crocidura sp.), Grey vole (Microtus arvalis/levis), and Macedonian house mouse (Mus macedonicus). In the diet of the Eastern imperial eagle I found some steppe elements such as the European souslik (Spermophilus citellus) and the Mole rat (Spalax leucodon).
4. Discussion4.1. Morphological dataThe teeth of Bulgarian Grey hamsters are close or almost identical to these from Greece, Turkey, and Syria in size and morphology, but hamsters from Romania and Moldavia are bigger than Bulgarian ones (Table 3).
The earliest records of the species in Bulgaria come from Early Pleistocene, from Cave 15 (Popov, 1994). In the Holocene and Late Pleistocene this species has been found in all fossil assemblages in Bulgaria (Peshev et al., 2004). The fossil hamsters were slightly larger than recent ones; this phenomenon is peculiar compared to other Pleistocene mammals (Kurtén, 1968).
The earliest records of the species come from Anatolia (Turkey): Early Pliocene from İğdeli (Alpaslan et al., 2010) and Early Biharian (Early Pleistocene) from Bıçakçı (van den Hoek Ostende et al., 2015). The first records from Europe are from the Early Pleistocene from Tourkoubounia 2 (Greece) (van der Meulen and Doukas, 2001) and Cave 15 (Bulgaria) (Popov, 1994).
Figure 2. Distribution of Cricetulus migratorius in Bulgaria (1- Straka, 1962; 2- Simeonov, 1964a, 1964b; this study; 3–6- Milchev, 2009; 7–8- Markov, 1964; 9- Markov, 1960; 10- Peshev et al., 1960; 11- Peshev et al., 1960; this study; 12- Georgiev, 2004; this study; 13–14- Georgiev, 2004; 15- this study).
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Rossolimo (1979) studied the geographical variation of the Grey hamster based on extensive material (22 collections and 230 specimens); she found that temperature is the main factor that drives its variation. In this species there is no clear direction of variation (cline), but rather a “mosaic-cline type of variation” (sensu Rossolimo, 1979). According to Gromov and Erbajeva (1995), mountainous forms are bigger than the forms from lower altitudes.
There is great individual variation in coloration within the species, even within the same location (e.g., Kabul, Afghanistan) (Niethammer, 1982). Maybe because of these patterns of variation more than 20 forms were described (Ellerman and Morrison-Scott, 1966; Gromov and Erbajeva, 1995).4.2. Distribution of Cricetulus migratorius in Bulgaria, with comments on its status in the BalkansI confirmed the presence of the Grey hamster only in south-eastern Bulgaria. In northern Bulgaria there was only one location, which has not been confirmed for more than 50 years (Straka, 1962). Extensive materials (14,227 small mammals) from the diets of Barn owl, Little owl,
and Long-eared owl from this part of country have been checked, but the species was not found, suggesting that it probably went extinct there.
In Dobrogea (where the northern locality is found), there is intensive agriculture with all accompanying practices (deep ploughing, heavy use of rodenticides, and autumn burning of arable and abandoned fields), which negatively impacts the population of the Grey hamster and the other two hamster species, Mesocricetus newtoni and Cricetus cricetus, living in this part of Bulgaria (N. Nedyalkov, unpublished data).
In south-eastern Bulgaria the socioeconomic conditions are different; mainly there is less anthropogenic pressure. This is due to the depopulation of the region, which has been happening since the 1990s, mainly as a result of demographic tendencies such as migration of people to big cities, aging of population, etc. This region is amongst the least populated in Bulgaria (32–40 people/km2; data from 2013 for the Yambol region, http://www.nsi.bg/, National Statistical Institute). Locally, agriculture is carried out on small and fragmented arable patches, surrounded by abandoned fields.
Table 3. Length and width measurements and the number of molars per specimen of Cricetulus migratorius from some recent and fossil populations. EB – Early Biharian, LV – Late Villanyian.
Locality Age ReferencesLm1 Wm1
Mean Min Max N Mean Min Max
Kazakhstan (Melkosopochnik) Recent This study 1.56 1.5 1.7 12 1.00 0.95 1.05
Greece (Tourkoubounia 2) Early Pleistocene (EB) van der Meulen, Doukas, 2001 1.86 1.73 1.98 15 1.14 0.99 1.21
Turkey (Bıçakçı) Early Pleistocene (LV) van den Hoek Ostende et al., 2015 1.52 1 1
Turkey (İğdeli) Early Pliocene Alpaslan et al., 2010 1.71 1.65 1.76 4 1.02 1 1.05
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There are no new data about the habitat preference of the Grey hamster in Bulgaria. Studies that utilised traps revealed that the species is caught predominantly in cereal fields, hedges, and orchards (Peshev et al., 1960; Straka, 1962; Markov, 1964), with an unusual record from a forest clearing (Markov, 1960). Multiple authors reported that the Grey hamster enters houses and grain storage facilities, including reports from Armenia, Turkey, and Iran (Sosnikhina, 1950; Kryštufek and Vohralík, 2009 and references their). According to Sosnikhina (1950), the population of the Grey hamster in natural habitats in Armenia is very low, in contrast to human settlements where it was a dominant small mammal.
In Romania the species occurred in the eastern part on the border with Moldova (Hamar, 1962); the most recent species distribution was summarised by Murariu (2000). There are no recent findings on the species (since 1973), but this is likely because of the lack of investigation in the region (G. Chisamera, personal communication).
In Greece the Grey hamster is reported from the Peloponnese peninsula (Kahmann, 1964; Ondrias, 1966, Niethammer, 1974). Recently the species has been reported from two locations there (Hymettus and Avlona) (Alivazatos et al., 2005), and from several localities from Thessaly (Bontzorlos, 2009), all data coming from the diet of the Barn owl (Tyto alba). The Grey hamster was present in low numbers in the diet of Barn owl from Greece: 0.56% (from 29,061 prey items) from Thessaly (Bontzorlos, 2009), 1.1% (from 152 prey items) from Hymettus, and 1.4% (from 94 prey items) from Avlona. According to Kryštufek et al. (2008), the Grey hamster is probably extinct from
Greece. А revision of the species’ conservation status in the IUCN Red List is needed.
The localities of my recent findings of the Grey hamster are geographically close to areas in Greece that lack records for the species at the moment; especially given that the species is widespread in the Turkish part of Thrace (Kryštufek and Vohralík, 2009), I presume that the lack of records in this region of Greece is due to insufficient search efforts.
In conclusion, it can be presumed that, in the western part of its range (Romania, Bulgaria, and Greece), the species is rare and in low numbers. In terms of further research, additional efforts for determining the species’ distribution and status in the Balkans are needed. Molecular genetic methods should be used considering the great morphological variation of the species, especially in order to reassess the species’ taxonomical status, which currently postulates two subspecies, C. m. atticus (for Greece) and C. m. vernula (for Bulgaria) (Niethammer, 1982).
AcknowledgmentsI thank D Demerdzhiev for providing me with the materials from the Imperial eagle and help with field work, and D Georgiev for the prey items from the Barn owl. I am grateful to Y Marinov for data on the vegetation in the region. I thank Hír János, Gabriel Chisamera, and Ebru Diker for aid with finding published literature. The greatest thanks go to the anonymous reviewers, who provided helpful comments that significantly improved the manuscript. Gratitude is also extended to Yurii Kornilev, who significantly improved the language of the paper.
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