Preliminary Assumptions for Identification of the Common Hamster (Cricetus cricetus) as a Service Provider in the Agricultural Ecosystem

The common hamster is a critically endangered species, but it is also perceived as a pest. Searching for an economic reason for its protection can be an argument to prevent its extinction. The purpose of this paper is to reveal the identification services provided by hamsters in the agricultural ecosystem and the determination of their correlation with human welfare. We propose the methods that can be applied for this purpose, and we check if the knowledge of the species is sufficient in order to use available methods for estimating the value of the services. The common hamster is a provider of supporting, regulating, and cultural services. Estimating their value is difficult because (1) available knowledge on the species’ ecology requires an update, in many aspects, due to changes to agricultural practices that have taken place since the 1970s (e.g., assessment of actual losses to cereal, vegetable, or root crops), and also extending by context, enabling the economic valuation of services (e.g., determination of impact range on various habitat components); it is also necessary to identify the correlations between profits and losses caused by this species; (2) there is a low level of public knowledge on the presence of hamsters and their role in the ecosystem. Education, primarily for consumers, followed by the promotion of hamsters as an umbrella and key species for agricultural areas, may result in the development of cultural services, which will increase the economic value of the services provided by hamsters.


Introduction
Agriculture is currently identified as one of the primary sources of environmental degradation [1]. Working on an agricultural farm has become a profession geared to increasing profit from sales of arable crops. Improving cost-effectiveness is associated with, among other things, reduced biodiversity of agricultural areas. The negative effects of biodiversity loss are not, however, directly felt on a small scale of an individual farm, especially in the short term. Thus, the vast majority of unnoticed benefits derived from the ecosystems is the effect of a complex ecological process, the outcomes of which are frequently delayed in time, while the resulting changes are of a non-linear nature. Hence, the ecosystem pressure increases gradually until it reaches the threshold at which certain ecosystem functions are disrupted [2]. The effects of this pressure are difficult to project due to the unobvious role of individual species, correlations between living and non-living ecosystem components, and the consequences for the process of service provision by the ecosystem. For example, the control of weeds or organisms causing losses to arable crops Sustainability 2021, 13, 6793 2 of 22 results in higher cost-effectiveness of micro-scale agricultural production in the short term. It needs to be noted, however, that the controlled species constitute a food base for the organisms at higher levels of the trophic chain or function within antagonistic interactions, limiting the increase in their density. Thus, the elimination of one species may have a negative impact on agricultural producers over a long period. The effects of environmental degradation are also not felt by the consumers of arable crops.
Persuading agricultural producers as to the need for protecting certain species, in particular, those perceived as pests, without specific and well-grounded argumentsprimarily of an economic nature-and without any support from state authorities, does not bring about the expected results. This is where the concept of ecosystem services comes to our aid. It gives the opportunity for the protection of nature since it emphasizes the correlations between the quality of human life and the quality of ecosystems and addresses universal thinking in economic categories. This concept indicates that nature conservation is both profitable [3] and an economic necessity [2]. It can be particularly helpful in protecting species at the edge of extinction due to deliberate control since it enables estimation of the relationship between profits and losses that result from their impact on the environment. The common hamster (Cricetus cricetus) may act as a perfect example; identifying the benefits derived from its presence in the functioning of the agricultural ecosystem may act as a baseline for more detailed analyses and determination of the resulting economic benefits. In 2020, the hamster was included in the IUCN list as a critically endangered species [4]. If the actions for its protection are not intensified, the hamster will most probably disappear from the natural environment within the next 20-30 years [5]. Apart from the causes of degradation of the hamster population that do not result from human activities, such as climate change, the functioning of this species depends mostly on changes to agricultural ecosystems and farmers who are reluctant to accept the concept of its protection and frequently unaware of the hamster's current legal status, treating it like a pest. These outcomes may lay the foundation for discussions between various groups of stakeholders, for example, on the determination of the amount of financial support for the farmers in agricultural and environmental programs or increasing the prices offered for arable crops harvested at the areas of particular importance for species protection. The fact that payments to farmers are the key to success in the approach to the protection of common hamsters was stated by different authors from western Europe, where many expensive programs aimed at protecting this species have been implemented [6,7]. Knowledge of economic benefits from the presence of hamsters can enhance the understanding between policy decision-makers and agricultural producers. It may also convince the decision-makers at the level of state administration that taking the actions targeted towards species protection is more cost-effective at the stage of the population functioning in its natural environment rather than when it no longer exists in it. According to Kronenberg et al. [8], there is difficulty in applying the concept of ecosystem services to an individual species. The reason for this difficulty is that natural processes are a source of profit for human beings, while an individual species is just a tiny link in these processes. Despite this fact, such attempts have been made, e.g., the identification of the ecosystem services provided by golden jackal Canis aureus [9]. The identification of benefits from the presence of hamsters, followed by estimation of their values, seems to be necessary and purposeful. In that paper, we want to check whether the concept of ecosystem services can be applied to the common hamster. Applying the concept of ecosystem services requires, first, identifying services provided by the species and, next, checking if the knowledge base of the species is sufficient to estimate the value of the service using the available valuation methods. Therefore, we have defined three specific purposes of this paper:

1.
Identification of specific services provided by the common hamster in the agricultural ecosystem and the determination of their correlations with human welfare; 2.
Review of the methods that can be applied to the service valuation; 3. Identification of the areas of knowledge in the field of hamster biology, which requires updating the current research to enable a detailed estimation of service values using available methods.

Materials and Methods
The article is a review. Achieving the set goals required a review of publications on common hamster biology and ecology in the context of defined services.

Classification of Services Provided by the Common Hamster
On the basis of MEA classification [10], we determined the basic categories of services (provisioning, supporting, regulating, and cultural), and, within them, based on the knowledge of the biology and ecology of the species, we initially identified the individual services provided by the common hamster. Next, we conducted a literature search on each of the services using the Google engine.

Literature Review
The literature review was conducted by means of the Google engine in Polish and English. We used keywords connected with the identified services provided by the common hamster, and, with the subsequently selected publications, we also added the keywords used by the authors of these works. The subsequent papers were reached using the snowball method, i.e., seeking the papers quoted by other authors. In the results, we collected 78 publications (peer-reviewed and review articles, nature monographs, reports, and conference presentations, as well as doctoral dissertations and Master theses), directly or indirectly addressing the issue of the hamster-agricultural ecosystem relationship, which enabled a discussion of the services provided by the common hamster for agricultural producers. The collected articles comprised: 44 publications on the biology and ecology of the species; 34 papers not directly connected with the hamster but addressing the issues of natural processes or relationships with the components of the habitats where the hamster occurs.
The second thematic module consisted of papers on the methodology of valuing ecosystem services. We gathered 19 publications in Polish and English.
Concerning the basic conceptual assumptions of ecosystem services valuation, we considered the theoretical or/and practical applications of the service valuation method. Subsequently, we analyzed the assumptions of each method, and, for each service, we selected the methods that might constitute a research workshop for the valuation of individual services provided by the hamster, together with suggested subjects of evaluation for future research.

Services Provided by the Common Hamster in the Agricultural Ecosystem
The services provided by the common hamster in agricultural ecosystems were qualified for four categories: provisioning, support, regulating, and cultural services. Within the categories, tangible benefits were identified as a result of the species functioning in the agricultural environment and contributing to the increased effectiveness of crop production. A conceptual scheme of the relationship between the services provided by the common hamster and existing, lost, and potential benefits for agricultural producers is presented in Figure 1. The rural population in the territory of today's Germany consumed hamster meat in the past while hamster liver was considered a delicacy. Hamsters and their hoarded food have also been used for poultry and pig feeding [11]. In Poland, we consider, in particular, the fact that their rural population was permanently undernourished, while the volume and quality of consumed food covered over 50% of energy demand [12]. In the periods of hunger that occurred in rural areas until the post-war era, including, in particular, preharvest periods, the population fed on anything that was available, including wheatgrass roots [13]. With regard to the above, in the regions of hamster occurrence, people used them as a source of food [14].

Skin trading
In Poland, the hamster has never been officially captured for skins; however, this activity is considered one of the main reasons for the decreased abundance of hamster populations in many countries throughout the entire area of species occurrence [5,15]. According to a review article by Surov et al. [5], from the 1950s to the 1970s, the number of captured animals in different parts of Germany fluctuated between 500,000 to more than 1,300,000. In eastern Slovakia, it was from 100,000 to more than 400,000, while in the former Soviet Union, it was from 300,000, on average, to a maximum of 16,000,000; in Hungary, the number of captured animals was from 1,500,000 to 2,400,000 and, in Romania, from 178,000 to 240,000. Capturing hamsters still continues, for example, in Hungary, where 1000-2000 animals are captured a day in the season of hamster activity [16].

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Hamsters as a source of food for humans The rural population in the territory of today's Germany consumed hamster meat in the past while hamster liver was considered a delicacy. Hamsters and their hoarded food have also been used for poultry and pig feeding [11]. In Poland, we consider, in particular, the fact that their rural population was permanently undernourished, while the volume and quality of consumed food covered over 50% of energy demand [12]. In the periods of hunger that occurred in rural areas until the post-war era, including, in particular, preharvest periods, the population fed on anything that was available, including wheatgrass roots [13]. With regard to the above, in the regions of hamster occurrence, people used them as a source of food [14].

Skin trading
In Poland, the hamster has never been officially captured for skins; however, this activity is considered one of the main reasons for the decreased abundance of hamster populations in many countries throughout the entire area of species occurrence [5,15]. According to a review article by Surov et al. [5], from the 1950s to the 1970s, the number of captured animals in different parts of Germany fluctuated between 500,000 to more than 1,300,000. In eastern Slovakia, it was from 100,000 to more than 400,000, while in the former Soviet Union, it was from 300,000, on average, to a maximum of 16,000,000; in Hungary, the number of captured animals was from 1,500,000 to 2,400,000 and, in Romania, from 178,000 to 240,000. Capturing hamsters still continues, for example, in Hungary, where 1000-2000 animals are captured a day in the season of hamster activity [16]. The total biomass of organisms on Earth has been estimated at 550 Gt of carbon, including the biomass of wild vertebrates of 0.007 Gt [17]. Biomass is of importance as a source of energy. In agricultural ecosystems, it is contained, among others, in the biomass of fauna or produced arable crops [1]. Hamsters are a part of the agricultural ecosystem biomass and, therefore, contribute to its total productivity.
The total biomass consists of the body mass of individual species, which, in the case of hamsters, depends on the age, sex, and physical condition of each animal and the season of the year. In adult individuals, it amounts to 158-830 g [18][19][20]. There are also certain regional differences related to hamster biometry [20,21]. No correlations between animal density and body mass have been established; however, there is a correlation between density and body mass increase rate in length [22]. It was also demonstrated that there is a positive linear correlation between the density and productivity of a population (calculated as a quotient of the number of captured animals aged 2-5 months and the number of animals after the first hibernation) and between population productivity and the length of the reproduction period. In the years with the highest hamster abundance recorded, adult animals grew faster and reproduced for a longer time period, which contributed to an increased productivity rate [22].
An attempt to estimate biomass production in the hamster population was taken in the 1970s by Górecki [19]. For an average number of 660 animals in the area of 128 ha, the author stated that the population productivity volume throughout the hamster lifespan (approx. 3 years) in the studied area amounted to 828.1 kg, i.e., approx. 6.5 kg/ha (including 1.03 kg/ha from reproduction and 5.43 kg/ha from body mass increase). The annual biomass turnover was estimated at the level of 1.4 kg/ha. The daily energy budget of a single animal was the highest in the activity months (40 kcal on average) and ranged between 10 and 22 kcal in the winter months. Total energy production in the population amounted to 1.12 × 104 kcal/ha/year.

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Participation in organic matter production and improvement of physical and chemical properties of the arable layer in soil Hamster is a species strongly associated with soil. It is included in edaphon megafauna [23].
Surdacki [24] stated that the hamster occurs in fifteen types of soil in Poland; however, it strongly prefers the soils formed on loessal and quasi-loessal substrates (47% of the total number of sites). A slightly smaller number (approx. 30%) was identified on podsolic soils formed on tills, loamy, and clay sands. Certain sites were identified on alluvial soils, loams, rendzinas, and soils with heavy clay formations, such as bedrock [24].
Hamster sites are usually located on arable lands classified as I, II, IIIa, IIIb, IVa, and IVb soils, which are soils assessed in terms of agricultural suitability as the best, very good, good, and medium good and of higher and lower medium quality [25]. The highest level of organization in plant production is recorded at the areas of common hamster occurrence, i.e., in the Lublin and Sandomierz regions and towards the north from the Krakow agglomeration, while a slightly lower level is recorded in the remaining part of the Lubelska Upland [26]. Intensive plant production is associated with numerous risks for soils and, as a consequence, for human welfare. Regular, deep tillage, the use of chemical fertilizers and pesticides, the removal of post-harvest remains (e.g., straw), and insufficient processing of organic matter (manure and compost) result in decreased humus resources and a growing risk of water and wind erosion, salinization, compaction, and steppe formation [27].

1.
Participation in organic matter production Humus content in soils in the territory of Poland ranges between 0.6-6%. Low-humus soil and soils of low humus content (organic matter content <2%) account for, depending on the region, 40-72% of arable lands [28]. In the plant production process, crops are removed from agricultural fields, which clearly results in, among other things, decreased humus content in soil by 40% in the last 10 years [28]. The hamster is the farmer's ally in the process of organic matter formation due to the fact that it hoards its food in larders, produces excrement, and becomes a part of organic matter after death. It is important that the vast majority of hamster sites are located in brown and podzolic soils (85% of recorded active sites) of relatively low humus content, while only 15% of sites are on humus-rich soils, i.e., black soils and rendzinas and alluvial soils, particularly when part of the humus in these soils is located below the arable stratum [26,28,29].
The single hamster produces approx. 1.2 g of dry fecal mass a day, which gives approx. 430 g per annum [30]. The vast majority of excrement is left in dedicated parts of burrows called latrines, at a depth of 1-1.5 m, i.e., below the humus stratum, which makes their decomposition a slow process, with a delayed return to the ecosystem. Hamsters of an average body mass hoard-within their activity period-approx. 110 g of cereals a day [19], which, between June and August, accounts for 2-3 kg on average [14]. In the case of hamster death, depending on the period, the material remains in the soil and returns to the ecosystem in time, forming humus or mineral and organic components of soil. It should be emphasized that hamster mortality within their activity period is differentiated and ranges between 3% and 43% per month [31][32][33]. The mortality rate in the hibernation period amounts to 50-60% [32], even up to 83%, of hibernated animals [34]. Most of the hamsters die due to the hoarding of insufficient volumes of food, which is proven by a lack of non-consumed food remains; however, the remaining hamsters die from diseases, burrow flooding, or advanced age [14]. The average hamster lifespan in natural conditions is estimated at approx. 7 months [19] to approx. 4 years [34]. Thus, the volume of organic matter produced by hamsters depends on population density, mortality rate, and volume of stored food at the time of animal death.

2.
Improvement of physical and chemical properties of the arable layer in soil When humus moves below the arable layer (<25 cm), the nutrients become inaccessible to the crop root system. The leaching of nutrients takes place as a result of, e.g., rains, in particular on large surfaces with no vegetation cover. In the years where rainfall volume exceeds evaporation, the soil becomes acidic because of the movement of alkaline nutrients [27]. At pH levels below 5.0, aluminum becomes toxic to plants. Hamsters contribute to reduced acidification of the soil by organic carbon sequestration; in deeper soil strata, it binds a certain pool of carbon for a longer time and reduces the release of carbon dioxide.
Another negative phenomenon is soil compaction, which increases soil density as a result of stress caused by heavy agricultural equipment. It results from the release of air and water from the soil and the destruction of soil pores, via which water, air, and nutrients penetrate the soil. Thus, soil compaction destroys organisms and underground sites [27].
In all these cases, hamsters and other soil-living species reduce soil degradation; the scale of its impact on the soil structure results from the size of underground burrows and tunnels built by this species.
Hamsters build permanent and temporary burrows. Permanent burrows are used for hibernation or functioning in the activity period; their size and complexity depend on the sex and age of the animal and the purpose of the burrow (Table 1). A burrow is composed of at least one chamber, with blind tunnels for excrement, and larger ones for food hoarding (larders). The chamber is accessible via 1-12 tunnels [35]. The diameter of entry holes to the burrows is 4-10 cm and depends on the age and sex of hamsters [36]. The length of tunnels varies and ranges from 0.3 to 26.2 m (3.9 m on average) [37]. Chambers of summer burrows are located at depths of 0.3 to 2.3 m, on average 80 cm below ground level [37], and winter burrows are located at a depth of approx. 2 m [26,34]. Tunnels are located below the arable and humus layers in the soil at a depth between 60 and more than 80 cm [35]. It may be calculated that the volume of soil to be excavated by a hamster to the surface in order to build a single tunnel is 0.015 m 3 , and, for the building of the single chamber, it is 0.006-0.02 m 3 (Table 1). Calculations do not include blind tunnels, larders, and latrines. Ziomek and Banaszek [35] estimated that the volume of soil excavated when building the burrows is approx. 1 m 3 . Considering the density of hamster burrows, it should be stated that the role of hamsters in slowing down the degradation of arable soils is relatively significant.
• Importance for biodiversity Loss of biodiversity decreases the agricultural ecosystem's capacity to handle, among other things, natural disasters such as floods, droughts, and extreme winds, as well as the negative effects of human activity, e.g., soil or air pollution. Maintaining biodiversity is, therefore, one of the essential actions for human welfare.
The hamster is a part of biodiversity ( Figure 2). It is known that the hamster is a victim of various species and that predation strongly affects its abundance, in particular at a low density of population [32,[38][39][40][41]. Hamsters are found in the diet of mammals, including domesticated predators [32,38,39,[42][43][44][45][46], and also in the diet of birds [6,32,39,47,48]. However, the importance of hamsters in the functioning of populations of different species is poorly known. According to research performed in Hungary [39], Slovakia [49], and Czech Republic [50], this species is of importance for the rare eastern imperial eagle Aquila heliaca, including in the periods of increased abundance of the rodent. Research on the steppe polecat Mustela eversmani's diet demonstrated that the common hamster is of slightly lower importance compared to the common vole Microtus arvalis [39,44]. Cserkész et al. [16] specified hamsters as a species of key importance for the occurrence of these two species. In different areas of Hungary and Romania, the share of remains of this rodent in the horned owl's Bubo bubo casts accounts for more than 60% [39,47]. O'Brien [7] stated that the decreased abundance of harriers Circus sp. in certain regions reflects a drop in the hamster population. In Poland, no research on the importance of hamsters in the functioning of predator populations has been carried out.
Recently, the issue of declining weeds in the agricultural landscape has been increasingly brought up [51]. Weeds are the source of humus; they supplement the activity of sorption complexes of soils, enable the development of soil microorganisms, and enrich soils in nitrogen and calcium. The low cover of weeds in the non-crop period protects the ground against drying and compaction by rainfall, which reduces the water and wind erosion of the soil and increases retention. Certain species are of importance for pollinators [52]. Weeds include several dozen endangered, critically endangered, and extinct wild species [51]. Rodents take part in spreading the weeds' seeds. Research on the potential of the common vole and the bank vole Myodes glareolus in this area has demonstrated that both species more willingly ate seeds rich in nutrients than seeds of low nutrient content [53]. M. glareolus prefers lighter seeds than heavier and seeds of common weeds than those of endangered species. No seeds germinated after their excretion with rodent feces, and there were only a few that recovered in full. That is why endozoochory as a service provided by rodents is of no importance. Rodents may spread seeds by hiding them in their larders [54]. The role of the hamster is difficult to specify since it hoards its food stores in larders below the soil layer in which the plants germinate. This method of seed storage is less favorable compared to dispersed and shallower hoarding [55]. Hamsters, however, may distribute seeds on their fur or in cheek pouches, from which they remove food in the case of threats. The large surface of the hamster's body, compared to other rodents, and its preference to build burrows in balks and wastelands [56] may be of importance.
The other aspect of the hamster's impact on biodiversity is the presence of arthropods in its burrows. The burrows have stable micro-climate conditions and provide plenty of food and bedding. Research by Celebias et al. [57], performed in 109 hamster burrows, demonstrated the presence of 73 invertebrate species in total, belonging to 16 families ( Figure 2). Most of them have great importance for soil biodiversity, taking part in the circulation of matter and energy, and are an important element of the trophic chain. There were also several rare invertebrate species, including Pycnota paradoxa, Cryptophagus schmidti, and Macrocheles matrius, that were particularly abundant. The variety of invertebrate species living in the burrows results from the preferences of hamsters to live in certain types of habitat.
The hamster is considered an umbrella species for agricultural areas [7,15,58]. This means that the protection of this species and its habitats enhances the protection of other species. The same changes to the agricultural landscape are indicated as the reasons for the decline of hamsters and, e.g., the lesser spotted eagle Clanga pomarina [59]. Alsace plans to award hamsters with flagship species status [6].
those of endangered species. No seeds germinated after their excretion with rodent feces and there were only a few that recovered in full. That is why endozoochory as a servic provided by rodents is of no importance. Rodents may spread seeds by hiding them in their larders [54]. The role of the hamster is difficult to specify since it hoards its food stores in larders below the soil layer in which the plants germinate. This method of seed storage is less favorable compared to dispersed and shallower hoarding [55]. Hamsters however, may distribute seeds on their fur or in cheek pouches, from which they remov food in the case of threats. The large surface of the hamster's body, compared to othe rodents, and its preference to build burrows in balks and wastelands [56] may be of im portance.
The other aspect of the hamster's impact on biodiversity is the presence of arthropod in its burrows. The burrows have stable micro-climate conditions and provide plenty o food and bedding. Research by Celebias et al. [57], performed in 109 hamster burrows demonstrated the presence of 73 invertebrate species in total, belonging to 16 familie ( Figure 2). Most of them have great importance for soil biodiversity, taking part in th circulation of matter and energy, and are an important element of the trophic chain. Ther were also several rare invertebrate species, including Pycnota paradoxa, Cryptophagu schmidti, and Macrocheles matrius, that were particularly abundant. The variety of inverte brate species living in the burrows results from the preferences of hamsters to live in cer tain types of habitat.
The hamster is considered an umbrella species for agricultural areas [7,15,58]. Thi means that the protection of this species and its habitats enhances the protection of othe species. The same changes to the agricultural landscape are indicated as the reasons fo the decline of hamsters and, e.g., the lesser spotted eagle Clanga pomarina [59]. Alsace plan to award hamsters with flagship species status [6]. Figure 2. Importance of the common hamster in biodiversity and determining the level of recognition of its impact, indicating taxa that are perceived as pests of agricultural crops or for which the hamster is of significant importance (including as a key species) (prepared on the basis of (1) [60]; (2) [57]; (3) [6,16,32,39,47,48]; (4) [16,32,38,39,[42][43][44][45][46]). In the study by Tissier et al. [60], the authors reviewed the available literature on the hamster diet. Among the crops taken by wild hamsters, different authors have listed 19 cereals, oilseeds, and fodder plants, as well as 11 species of vegetables and root species. The number of wild field plants covered 60 species, followed by 3 unspecified species from Asteraceae, Brassicaceae, and Graminae families and 22 tree and shrub species. Subject to the availability of plants classified as weeds, the vast majority of hamster diets are their seeds and leaves, particularly in the period of late spring, summer, and autumn [60]. The availability of wild flora species may partially replace the green parts of arable crops in the hamster diet, including in spring and early summer [61]. According to the studies collected by Tissier et al. [60], in which the share of individual species found in the burrows, stomachs, or cheek pouches of hamsters was determined, some of them accounted for up to 10% of the analyzed plant material. These species are presented in Figure 2. Many of them are species with a rapid growth rate, high resistance, and productivity, as well as a low threshold of economic harm. These thresholds specify at what abundance of the plant the losses in crops exceed the costs of chemical weed control [62]. An example of such a plant is the goosefoot Chenopodium album, which, at a density of 3-4 plants per m 2 , reduces plant yields [62]. Goosefoot may account for even 10-30% of hamster food in spring and summer [60].
The hamster-as a food opportunist-feeds on available food and, in the case of availability of weeds, reduces their volume. This may actually be of importance for weeds that have become resistant to the active substances used in herbicides, e.g., corn poppy Papaver rhoeas or mayweed Matricaria inodora [63].

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Reducing the density of animal species considered pests The share of food of animal origin in the hamster diet ranges between 6% and 16%, of which vertebrates account for only slightly above 3% [30]. The animals, including species treated as pests, are shown in Figure 2. Some of them have certain trends for regular mass appearances, while the greatest damage to crops in different parts of Europe is caused by the common vole [64]. In the territory of the Czech Republic, the common vole and wood mouse Apodemus sylvaticus and Ural field mouse Apodemus microps dominate the vast majority of crops, with a high preference towards medick Medicago sativa [65]. In the 1970s and 1980s, these species caused losses in medick production at the level of 80% in Poland [64]. Field vole Microtus agrestis and water vole Arvicola terrestris damage the root systems of fruit trees and shrubs [64]. Additionally, the common vole and hare Lepus europaeus may cause significant losses in apple orchards, reaching up to 97% of trees; 90% of lethal damage is caused by the vole [66]. Different authors have pointed out the need for controlling the vole population by rodenticides [64]; however, this method of crop protection has a negative impact on the protected species of predatory birds [67]. One environmentally friendly method is managing the habitats to enhance the biological control of their natural enemies [68].
The other group of organisms included in the hamster diet that may cause damage to arable crops, shrubs, or orchards is invertebrates (Figure 2). In the summer season, their share in the diet may account for approx. 6%, while in autumn, it increases to 13.4% of consumed food [30]. Different authors have identified, among others, the following invertebrates: Coleoptera beetles (including maybug Melolontha sp.), gastropods (including Limacidae), and scale-winged butterflies (including the larvae and maggot forms) [60]. There have been increased losses recorded in recent years, in particular in rapeseed production and horticulture, caused by Spanish slugs, a certain part of which is alien invasive species [69]. The larvae of butterflies, e.g., cabbage white butterfly Pieris brassicae, are a permanent issue of concern in cruciferous vegetable production. According to available information on the share of invertebrates in the hamster diet, it is known that these organisms are a component of the hamster diet; however, the hamster's impact on the invertebrate population remains undetermined.

Cultural Services
The potential of the hamster in ecosystem services is very high yet not fully used. This results from the fact that this species is hardly known in Poland. It is known primarily to the older inhabitants of rural areas. The impact of this rodent on the functioning of bygone rural communities has made this species a part of the regional tradition of many sites in Poland. It is expressed by different names for this rodent. There are 26 different names for hamsters in Poland, originating from observations of its behavior (e.g., bruin), associations with the sounds it makes (for example, chatter, barking rat, and field dog), and similarity to the other species (such as suslik, ground squirrel). Certain names are the Polish versions of foreign names (e.g., hamster) [35]. Young people, even those running an agricultural activity, due to different methods of cultivation (frequently from a tractor cabin), are usually unaware of the presence of this species at their fields. In Alsace, for example, the vast majority of young farmers have never seen a hamster [6]. In recent years, however, the situation has started to change and, therefore, the increase in the value of cultural services will depend on hamster promotion and education in order to form society's opinion of this species. The hamster (not necessarily the common hamster) is a symbol of retrenchment and foresight. It is also a symbol of gluttony. It frequently serves as an example of the most beautifully colored wild mammal [70]. Various gadgets and utility items (cups, t-shirts, backpacks) with images of hamsters have started to appear for sale. It is also an inspiration for nature photographers.
The best example of the promotion of localities with the use of hamster images is Jaworzno. In 2014, the foundations for the "Programme of active protection of the common hamster (Cricetus cricetus) for the city of Jaworzno" were developed, and, in 2016, an ecological site dedicated to this rodent was established [70]. Apart from active protection, the city implements educational and promotional activities. An educational brochure was published, and t-shirts and calendars with hamster images were offered for sale; the "Common hamster protection program in Jaworzno" website was created on social networking media. Competitions for children, with the city playing the role of host, were organised. The issue of species protection is touted by local media. The area of the ecological site has become an attractive place, visited by the inhabitants of Jaworzno. Educational boards have increased their ecological awareness of the hamster and the biodiversity of agricultural areas. On the initiative of city authorities, figurines of hamsters of a natural size have been placed in different parts of the city and act as a local attraction for citizens and tourists.
The Congress of the International Hamster Workgroup, with the participation of biologists and activists for hamsters from all of Europe, has been organized twice in Poland. One of them, the jubilee 20th Congress, was held in Poznan in 2013, while the 27th Congress took place in Jaworzno in 2020. Due to restrictions related to the pandemic situation in Europe, the participants from outside Poland could not attend; however, information on the activities in Jaworzno and the city itself reached different parts of Europe. In nationwide media, Jaworzno has been mentioned as the first locality in Poland in which actions for active protection of the critically endangered common hamster have been undertaken, and the city will always be associated with this fact. The other example of actions at the regional level is the trips to the hamster sites in Szczebrzeszyn, organized by a famous Polish naturalist at the occasion of a literature festival.
Since hamsters occupy the peripheries of various cities of Poland [46,[71][72][73][74], they have become a part of a system that enables education concerning nature, presenting the objectives and methods of agriculture. This is of importance due to the unfolding regress of knowledge of these issues in the younger generation. Well-performed education may act as an indirect method of promoting farmers, primarily these managing small farms. In certain regions, it may serve as an emblem, attracting those missing idyllic mosaic landscapes and promoting agricultural products of high quality. Thanks to these actions, the hamster may also contribute to the promotion and increased importance of landscape protection. The readiness of certain landowners to establish so-called private wildlife refuges poses an opportunity for tourist activities related to the hamster. This method of habitat protection is particularly promising for agrocenosis-related species, while the hamster may act as one of the flagship taxons used to promote this form [70]. It may enhance effectiveness and reduce the costs of the protection of this species and the biodiversity of the agricultural landscape.

Ecosystem Dysfunction in Economic Terms
The presence of hamsters in the fields is associated with losses in arable crops. The studies on the losses caused by hamsters in crops are derived mainly from the 1970s. According to Górecki and Grygielska [30], at a density of 6 hamsters/ha, losses caused by feeding amounted to 0.05% in summer and 9% of total cereal production in autumn. Thus, summer losses accounted for less than 1% per 1 ha of crops per animal, while before the hibernation period, up to 6% is lost to cereal hoarding [75]. Information on the volume of hoarded food indicates that it ranges between 0.05 to 15 kg [35,37,75,76]. In rare cases, when the hamsters hibernate in the vicinity of human settlements, there have been recorded cases of 34 kg of hoarded pea seeds [77] and 70 kg of hoarded potatoes and other vegetables [78]. The amount of food necessary to survive winter is 1-1.5 kg, and a single animal can hoard between 2 and 3 kg on average [14]. Górecki [19] estimated the amount of hoarded food on the basis of the volume of the food stored in the cheek pouches per hamster. According to him, a hamster weighing approx. 350 g stores 9.5 g of dry cereal mass at a time and leaves its burrow 12.3 times a day. Assuming that each trip is associated with food hoarding, a relatively small hamster hoards approx. 117 g of cereal a day. The food hoarding period lasts approx. 90 days (from August to October). In this period, a small hamster may hoard to approx. 10.5 kg of dry cereal mass at maximum. Górecki [19] stated that hamsters cannot hoard more than 15 kg, in agreement with other authors. Hamsters also contribute to losses by crop treading. The territory of a single animal consists of trodden, permanent paths used for movement. Diameters of a trodden surface around the most complex breeding burrows may reach even 2 m (own observations). The vast majority of burrows in the peak period of hamster population development, i.e., in August, are, however, the smaller burrows of young hamsters. It should be noted that more complex burrows, used by hamsters to hoard their food for winter or by females for breeding, are usually used for several years.

Review of the Methods Suggested for Valuation of Services Provided by the Common Hamster
Two approaches are used for the valuation of ecosystem services. The first approach uses direct methods based on the stated preferences and the revealed preferences. Direct methods are based on hypothetical markets and use survey techniques to test consumer preferences. The second approach is based on indirect methods by which a hidden value for non-market goods is inferred on the basis of the observable market-determined prices of market goods [79]. A number of the existing methods may be, under certain conditions, applied for the valuation of the services provided by the common hamster. However, it should be noted that the diversified nature of these services does not allow us to apply a single, universal method to estimate the economic balance of species impact upon an ecosystem. Instead, one should consider the application of various methods, depending on the kind of service, level of advanced knowledge, ecological awareness of consumers and agricultural producers, and limitations imposed by the assumptions of individual methods [80]. A summary of eight known methods is presented in Table 2. Table 2. Suggested valuation methods of the services provided by the common hamster.

Kind of Service Method Value of Service Description of Evaluated Object Conditions Enabling the Service Valuation
Source of food and skin trading (1) 1 Price of product Data on the historical value of skin or meat or on the value derived from the countries in which the hamster is still legally captured Biomass (2) 1 Energy price Energy taken by conversion of biomass into calorific values of tissue or on energy production volume in the population 2 Price of fertilizers Data on the volume of fertilizers, which are an alternative energy source necessary to ensure crop growth r (CH) Organic matter production (2) 3 Price that the consumer is ready to pay for arable crops Data on the volume of arable crops from farmers involved in "hamster-friendly" management. Such agricultural practices favor both the maintenance of proper content of organic matter in the soil and the presence of hamsters p (F), e (F) p (C), e (C) Improvement of physical and chemical properties of the arable layer in the soil (2) 2 Price of agrotechnical treatments Data on the value of treatments necessary for soil aeration and scarifying (e.g., tillage or subsoiling). The service value provided by the hamster is increased by the fact that the service is realized at a deeper level than subsoiling can be performed Price that the consumer is ready to pay for arable crops Data on arable crops from the farmers involved in "hamster-friendly" management. Such agricultural practices favor reduced soil degradation and promote the occurrence of hamsters p (F), e (F)) p (C), e (C) Importance for biodiversity (2) 4 The amount of spared public funds The common hamster is an umbrella or key species. The method requires the identification of protected species benefiting from the protection of the hamster, and then, the determination of the cost of actions aimed at the protection of each such species is compared to the cost of hamster protection The costs of restoration of habitat or species The value of service may be the cost of restoration of biodiversity or the cost of restoration of the hamster population in the natural environment, including the necessary habitat components 5 Price that the consumer is ready to pay for different variants of arable crops Consumers can be asked for preferences concerning the products originating from the areas of various levels of biodiversity, ranking different variants by value, and specification of the amount they would be willing to pay for each scenario p (C), e (C)) p (F) 6 Price that the consumer is ready to pay for arable crops The question may be asked on the price the consumers would be willing to pay for the products offered by the producers implementing sustainable development principles in their production process p (C), e (C)) p (F)  Prices of arable products not lost during the production process Feeding hamsters with alternative food, i.e., weeds and crop pests, results in decreased losses by means of elimination of organisms negatively affecting the crops and by intake of substitute food instead of arable crops. Thus, revenue from agricultural production will be higher r (CH)) r (F) 2

Prices of plant protection products
Knowing the impact rate of the hamster on populations of weeds and pests, an attempt to estimate the amount of rodenticides and herbicides necessary to eliminate the same quantity of organisms causing production losses may be made Price that the consumer is ready to pay for different variants of arable crops A price that consumers are willing to pay for agricultural products originating from farms using plant protection products compared to farms that use lower quantities of the products or none at all (and in which the hamster is present) All cultural services (4) 1

Prices of products and services
Value of trips and necessary infrastructure (accommodation, catering), gadgets, and agricultural products from producer groups associated with the emblem of the hamster can be used The amount of spared public funds When creating the opportunity to establish private refuges for hamster protection, it may be estimated how much their functioning relieves public funds from investment in a national species protection program. The costs of the work of volunteers enrolling for hamster monitoring should be counted p (F), e (F)) p (C), e (C) 7

Price of travel costs
The price that service recipients are willing to pay for access to a specific site or how far they will travel to see a specific site (for example, the ecological site in Jaworzno or the locations of hamster monuments in the city) p (C), e (C) 8

Prices of construction plots
The prices for a construction plot in a landscape where the hamster occurs compared with the prices of plots of a similar standard and distance from a large city at which the hamster is not present and where intensive plant production is conducted p (C)) p (F) (1) Provisioning services; (2) supporting services; (3) regulating services; (4) cultural services. 1. The market price method; 2. the replacement cost method; 3. the contingent valuation method; 4. the restoration cost method; 5. choice modeling; 6. the reservation price method; 7. the travel cost method; 8. the hedonic behavior method. C-consumers, F-farmers, CH-the common hamster; p-promoting; e-education; r-conducting or updating research.
The market price method (Method 1, Table 2) was suggested for each service category. It has a limited application due to no markets for the vast majority of ecosystem services [81]. It relies on estimating the value of services on the basis of the market prices of services connected with the market. In the case of services provided by the hamster, these may be, e.g., the prices of furs, meat, and energy (biomass energy), and also products created on the basis of the hamster image or services offered, such as education or nature tours. The method may also be used to value the hamster's share of the service of limiting the spread of crop pests. The value of this service may be the revenue from the sales of the products saved, owing to the hamster's activity. The value of provisioning services should be regarded in terms of lost benefits or from a historical perspective. The methods may be applied to estimate the losses in yields caused by hamsters. According to some authors, market prices are only approximate, determining the lower limit of values, as they do not consider the non-market mechanisms of price formation (e.g., subsidies) and they do not take into account non-use values [82,83].
The replacement cost method (Method 2, Table 2) may also prove very important. It involves estimating the costs of undertaking the activities necessary to replace the services provided by the species [9,82]. However, the application of this method requires a replacement facilities market. It may be, e.g., stating the amount and pricing of the fertilizers necessary for plant growth, corresponding to the energy obtained from the hamster population biomass. Another example may be estimating the value of agrotechnical measures necessary for the scarifying and aerating of soil. However, thorough research should be conducted, aimed at precisely determining the hamster's impact on, e.g., soil, plant yields, and pest populations.
In the case of services involving the hamster's impact on soil, the contingent valuation method may be used (Method 3, Table 2). It is a survey-based method of direct acquisition from the respondents of the information on their willingness to pay for a given environmental good and the amount of such payment or their willingness to accept compensation for tolerating any negative changes in the environment or access to it [84]. The method has been used, among others, to value rare and endangered flora and fauna species [85,86]. Its possible application to the service provided by the hamster is due to the fact that agricultural practices favoring soil protection also favor hamster occurrence. However, the application of this method requires the education of agricultural producers and consumers; it requires the promotion of the hamster as the species whose occurrence reflects the realization of sustainable agriculture practices. Consumers who are aware of the causes and results of soil degradation and the impact on hamsters on this part of the agricultural ecosystem may state their preferences.
The restoration cost method (Method 4, Table 2) is most valuable and useful for the valuation of hamster importance in biodiversity. In this method, the valuation is done on the basis of the cost of actions taken to renew or rehabilitate environmental resources [84]. In the United States, this method has been officially adopted to support spatial planning decisions [87]. From the perspective of the activities aimed at hamster protection, the method may prove an excellent tool for presenting economic arguments for the intensification of efforts in this direction, both on macro and micro scales. The hamster is an umbrella species. The first step for this method's application is the identification of species that would benefit from habitat protection and then the estimation of the cost of activities to be undertaken for the protection of each of them. The value of the service is the amount saved on the realization of a single species protection program instead of several separate programs. The hamster is also a key species whose loss entails a decrease or loss of biodiversity on other levels. The value of the service may constitute the cost of habitat biodiversity restoration to the original level or the cost of hamster population restoration in the natural environment. Currently, the estimated value of the service may constitute the costs involved in the implementation of the "Common Hamster Protection Programme in Jaworzno". The method may also be used in the cultural services group on the condition that the appropriate institutions will develop the rules for creating private wildlife refuges for hamster protection and the education of society. These refuges will relieve public funds from investing in a national program of environmental protection. Currently, the actual value of the service consists of, among others, the costs saved due to volunteers' work in national hamster monitoring.
The reservation price method (Method 6, Table 2) and the choice modeling method (Method 5, Table 2) require survey research conducted on a random sample of respondents. In the first case, the respondents declare the amount they are ready to pay for the service. In the other method, they determine the ranking of the alternatives connected with individual services and choose among them [88]. The choice of the most preferred alternative is easier for the respondents; it is more a comfortable and natural method than a direct definition of the service value in monetary units [89]. These methods may be applied, e.g., for the evaluation of hamster importance for biodiversity or the estimation of the value of regulating services. Application of the reservation price method allows us to ask about the price that respondents would be ready to pay for the products from the farmers following the practices of sustainable development in the areas of hamster occurrence or areas where various levels of plant protection chemicals are applied. Currently, the reference point may be a comparison of the prices of products from organic farms with the prices of products obtained in the intensive farming process in the areas where the hamster occurs. The condition for both methods is the promotion of and education on hamster importance for biodiversity and the consequence of its loss on the agricultural ecosystem, conducted in the producer group, as well as the provision of information on the consequences of plant protection chemical application on biodiversity and human health.
Two methods that are not used for the other service groups may be applied to the area of cultural services. The first is the travel costs method (Method 7, Table 2). It is used mainly for the evaluation of valuable natural areas [84,90]. The economic value of individual resources or the services that they provide is identified by the cost of travel and the value of the time spent getting to a given location (estimated on the basis of lost earnings). In the broadest sense, the travel cost is regarded as the total expenditure incurred by tourists (e.g., travel costs, accommodation, board admission tickets) and the value of dedicated time [91]. The application of the method requires data on the number of visits in the studied locality, the travel costs sustained by the visitors, and the time of travel. The higher the value of a given area or object for tourists, the greater their willingness to spend on travel. The value of the service will be higher with an appropriate promotion of hamster sites (e.g., landscape parks, ecological sites in Jaworzno, the places where hamster statues were placed in the city). The other method is the hedonic behavior method (Method 8, Table 2), which involves the assessment of ecosystem service impact on the prices of products and market goods connected with them [92]. A price of a selected market good, linked with the environmental good, is broken down into the sum of attributes composing the good [93]. The method allows us to determine how the price of the good will change if a given attribute changes, whereas the difference in the price of market goods is described as the value of non-market goods connected with the changed attribute. Taking into account picturesque agricultural landscapes where the hamster occurs, it is possible to, e.g., estimate the prices of building plots in these localisations compared to plots of a similar standard and distance from cities but located in the areas of intensive farming where the hamster does not occur. In order to increase the value of the service, the hamster may be promoted as a part of a certain type of landscape promotion. Drawing reliable conclusions is associated with the necessity to organize a large research sample because market prices are formed by random factors.

A Need for Supplementing or Updating the Research on the Common Hamster
A part of the valorization process of the services provided by the European hamster must be the research conducted in the many areas of biology and ecology of the species (Table 2). Without this, estimating the real value of individual services is impossible; currently, we only have the opportunity to speculate. Numerous results of studies conducted in Poland on the hamster are out of date. An example is the research carried out in the 1970s on the losses caused by hamsters [30,75]. Updating the knowledge on the losses in crops suffered by farmers due to the presence of hamsters (estimated as % per 1 ha) requires both the estimation of lost crops and crop yields and the availability of various foods. Since the 1970s, there have been significant changes in these aspects. According to Gorzelak [94], the yield of the main crops consumed by the hamster in Poland has increased between the 1970s and the first decade of the new millennium-wheat (from 29.3 to 39.4 q/ha), rye (21.6 to 23.7 q/ha), barley (27.6 to 32.5 q/ha), oats (22.8 to 25.1 q/ha), potatoes (177 to 207 q/ha), and sugar beets (280 to 513 q/ha). Corn yield increased from 23.5 to 127.8 q/ha; its share in plantation grew significantly. A noticeable increase in crop yields was recorded primarily in the eastern parts of Poland, currently inhabited by hamsters. This means that the percentage of losses caused by this species is lower than in the 1970s and requires verification. The heaviest losses may include these caused in spring when hamster feeds on early vegetables [95]; however, the actual losses have not been studied yet. When estimating the losses, the technological changes in cultivation practices should also be considered. These have led to the deterioration of the hamster feeding base, which is composed mainly of wild flora species. In numerous studies on the hamster diet, conducted since the 1970s, there have been 125 taxons indicated in total, of which only 31 are arable crops, while the remaining ones are weeds, trees and shrubs, and foods of animal origin [60]. Limited access to wild flora species may, therefore, play a significant role in the losses caused by hamsters in crops. The composition of the hamster diet (n = 264), captured at different sites, was studied in Slovakia [96]. The diet of hamsters inhabiting the sites of a large share of wasteland and high biodiversity of plants consisted of 41 identified plant taxons, while at the site dominated by arable fields, only 7 plant taxons were identified. Unfortunately, research on their diet in agricultural areas, with consideration given to the available food base, originates mostly from the 1970s. In later periods, the vast majority of authors carrying out research on the hamster diet have studied its composition without determining the availability of plant food in the hamster's territory [60]. According to the observations of Ziomek [61], the share of weeds in the hamster diet is significant, in particular during periods of low quality and volume of arable crops. Hamsters feed intensively in wastelands, in particular between April and the end of June. Current research on the use of flower fields, created for pollinating insects, by the hamster indicates that burrow concentrations in these areas are higher than their density on the adjoining arable fields, where it has been constantly low [56]. Hamster occurrence in the flower fields was negatively correlated with plant density and grass cover of these areas but positively correlated with the distance from the nearby forests, the share of arable lands, and the wastelands around the arable lands. Despite the hamster's known preferences for areas different than arable fields, there is still a need for studies on the impact of hamsters on weed communities in fields, particularly herbicide-resistant species (Table 2). Still, no research has been conducted on the unequivocal relationships of hamsters with other rodent or invertebrate species regarded as pests. According to the observations of persons performing hamster research, the number of burrows of various rodents in certain sites is higher in the fields where no hamsters are present compared to the fields where this species occurs. It seems that, for example, voles may form larger colonies at the sites not occupied by hamsters (Hędrzak and Eichert, own observation). This thesis also requires verification and explanation. The results of the research will lay the foundations for the estimation of their actual impact on the functioning of wild flora and fauna species. In terms of the services provided by the hamster, the issue of losses in crops should be analyzed jointly with studies on regulating services and the importance of biodiversity, including the spreading of weed seeds.
Studies on the correlation between the hamster's capacity for removing weed seeds and the level of losses caused in crops have been conducted for the other rodent species, such as Apodemus spp. mice feeding on cereals, herbivorous voles Microstus spp., and the omnivorous bank vole. They revealed that the dominant species in the studied area was common vole [97]. The daily rate of goosegrass Galium aparine seed intake was not correlated with the number of rodents. It demonstrated, however, a positive correlation with the diversity of crops and the length of field edges. The rate of wheat seed intake increased with cereal increase and was almost three times higher compared to the rate of weed seed removal. This rate also demonstrated no correlation with the management method (organic/intensive farming) and landscape diversity. For hamsters, these correlations need to be specified.
While considering the services provided by the hamster, one should also take into account the fact that since the 1970s, the species morphology has changed, and, currently, hamsters have a lower body mass on average [20], which may be associated with lower amounts of consumed and hoarded food. So far, the area trodden by hamsters, where plant emergence is impeded, has not been determined.
Another important area that should be researched is hamster importance for biodiversity ( Table 2). It is generally known that the hamster is an umbrella species. Although, intuitively, one may suppose that its protection serves other agroecosystem species, yet the research in this area has not been conducted, and, in Polish conditions, these species have not been indicated. The issue of the hamster as a key species has not been solved either, although, in the countries like Hungary, Slovakia, Czech Republic, and Romania, it has been specified as an important species for the occurrence of some predatory birds and the steppe polecat [16]. It may result from the fact that the majority of agricultural landscape predators in Poland are food opportunists. However, it seems necessary to undertake the research on hamster importance on predators' diet, particularly locally, in the areas where this rodent is numerous.

Discussion
In the scope of the methodology of estimating the value of ecosystem services, selecting a single and mandatory set of methods is impossible. Only in the case of provisioning services, the vast majority of them can be described in a relatively unambiguous manner by the market value of the produced goods [98]; however, this group of services should be remembered in historical terms.
For different types of services provided by the hamster, less unambiguous valuation methods must be applied. This species definitely provides supporting and regulating services. At the current level of knowledge on hamsters, it is, however, difficult to estimate their value due to the lack of research. In the context of services for agricultural production and with regard to the negative attitude of farmers to hamster protection, the most urgent need in terms of research is, therefore, establishing the correlations between the benefits from its occurrence and the losses caused to crops. Similar research has been performed for the other rodent species [97]. According to them, this correlation is not unambiguous; the scheme of occurrence of losses or their economic relation to the services provided by specific rodent species onto other species cannot be extrapolated. In Poland, the hamster is highly differentiated in terms of local density, point occurrence, and even within a single site, where it will move with the crop structure. Thus, consideration of the spatial range of losses is of key importance when determining the profit-to-loss ratio with reference to hamster occurrence. Agricultural producers with hamsters on their fields for one year may suffer no losses due to the presence of this species in the next year.
The developing cultural services feature a high potential in terms of creating a market of services provided by the hamster. Appropriate species promotion and the skillful creation of its image may be beneficial in many aspects. Promoting the localities in which the hamster is no longer present may take the form of including it in regional history and language. Promoting the localities in which hamster continues to live seems to create more opportunities that translate into specific benefits to the inhabitants. Emphasizing the fact that the hamster is an endangered and umbrella species may increase tourist interest in visiting its habitats and the interest of consumers in products from the farmers involved in hamster-friendly agriculture and, therefore, maintain biodiversity and the agricultural landscape. This may become of particular value for the farmers involved in direct sales from small farms and organic farms that may use the hamster as an emblem, e.g., for small producer groups. Dynamically developing bottom-up initiatives, so-called food cooperatives, prove that consumers have a need to "get closer" to producers to somehow control the quality of the purchased products. Such cooperatives will link people, usually living in the cities, with the farmers to purchase crops directly from the farm. The success of cooperatives lies in building mutual trust in producer-consumer relations. This relationship creates space for introducing the protection of common hamsters. Promoting the species among consumers as a guarantor or ambassador of the economy, favoring the protection of the agricultural environment on a wider scale, may affect the prices of products and change the perception of producers, i.e., the group on which the fate of this species largely depends. In effect, benefits will be brought to all, that is, the consumers will gain by purchasing healthier products, the producers by increased revenue from sales, and the species itself from to the changed attitude of the producers to its protection, by raising ecological awareness in the group of consumers. However, such an approach requires a certain time and well-thought and planned actions in the fields of education and the promotion of the common hamster to different groups. The application of the proposed methods based on surveying groups of respondents for the purposes of valuation of cultural services faces certain difficulties, resulting mainly from poor knowledge of the common hamster. Although various cultural services provided by the species continue to develop slowly, the core service from this group remains and should be education. This statement complies with the opinion of various authors, who have perceived education as a key opportunity to increase the effectiveness of common hamster protection [6,14,35,46].

Conclusions
This article presents, for the first time, the known facts of the biology and ecology of the common hamster in the context of the services that the species provides. We have shown that it provides supporting, regulating, and cultural services. However, this is only the first step towards estimating their value. Currently, making such an estimate with the use of available methods raises significant difficulties. There are two reasons for this situation. Firstly, the available knowledge on species ecology requires (1) updating in many aspects, (2) extending by context, enabling the economic valuation of services. It is also necessary the identification of the correlations between profits and losses caused by this species. The second issue is the low level of society's knowledge of the presence of hamsters in the environment of arable lands and their role in the ecosystem. The education of consumers and farmers, followed by the promotion of hamsters as an umbrella and key species for agricultural areas, may result in an increase in awareness and the development of cultural services. Since hamsters are perceived as pests, activities related to a change in this image, including economic arguments, are of the utmost need.