The Effects of Urbanization — Small Mammal Communities in a Gradient of Human Pressure in Warsaw City, Poland

Pathogens detected in ticks (Ixodes ricinus) feeding on red squirrels (Sciurus vulgaris) from city parks in Warsaw

The European red squirrel (Sciurus vulgaris) is a common host for Ixodes ricinus ticks in urban and rural habitats, however, studies on ticks and tick-borne pathogens (TBPs) of squirrels have not been conducted in Poland yet. Thus, the aims of the current study were to assess and compare the prevalence and abundance of ticks on red squirrels trapped at two sites in the Warsaw area (in an urban forest reserve and an urban park) and using molecular tools, to assess the genetic diversity of three pathogens (Borrelia burgdorferi sensu lato, Rickettsia and Babesia spp.) in I. ricinus ticks collected from squirrels. For the detection of Rickettsia spp. a 750 bp long fragment of the citrate synthase gltA gene was amplified; for B. burgdorferi s.l. 132f/905r and 220f/824r primers were used to amplify the bacterial flaB gene fragments (774 and 605 bp, respectively) and for Babesia spp., a 550 bpfragment of 18S rRNA gene was amplified. In total, 91 red squirrels were examined for ticks. There were differences in tick prevalence and mean abundance of infestation in squirrels from the urban forest reserve and urban park. Three species of B. burgdorferi s.l., Rickettsia spp., and Babesia microti were detected in ticks removed from the squirrels. Our results broaden knowledge of S. vulgaris as an important host for immature I. ricinus stages and support the hypothesis that red squirrels act as a reservoir of B. burgdorferi. Moreover, we conclude that red squirrels may also play a role in facilitating the circulation of other pathogens causing serious risk of tick-borne diseases in natural and urban areas.

What makes a house a home? Nest box use by West European hedgehogs (Erinaceus europaeus) is influenced by nest box placement, resource provisioning and site-based factors

Artificial refuges provided by householders and/or conservation practitioners potentially represent one mechanism for mitigating declines in the availability of natural nest sites used for resting, breeding and hibernating in urban areas. The effectiveness of such refuges for different species is, however, not always known. In this study, we conducted a questionnaire survey of UK householders to identify factors associated with the use of ground-level nest boxes for West European hedgehogs (Erinaceus europaeus), a species of conservation concern. Overall, the percentage of boxes used at least once varied with season and type of use: summer day nesting (35.5-81.3%), breeding (7.2-28.2%), winter day nesting (20.1-66.5%) and hibernation (21.7-58.6%). The length of time the box had been deployed, the availability of artificial food and front garden to back garden access significantly increased the likelihood that a nest box had been used for all four nesting types, whereas other factors related to placement within the garden (e.g., in a sheltered location, on hardstanding such as paving, distance from the house) and resource provisioning (bedding) affected only some nesting behaviours. The factors most strongly associated with nest box use were the provisioning of food and bedding. These data suggest, therefore, that householders can adopt simple practices to increase the likelihood of their nest box being used. However, one significant limitation evident within these data is that, for welfare reasons, householders do not routinely monitor whether their box has been used. Consequently, future studies need to adopt strategies which enable householders to monitor their boxes continuously. Ultimately, such studies should compare the survival rates and reproductive success of hedgehogs within artificial refuges versus more natural nest sites, and whether these are affected by, for example, the impact of nest box design and placement on predation risk and internal microclimate.

Distribution of Small Mammals (Eulipotyphla, Rodentia) in the Gradient Direction Urban–Suburban–Rural of Central Slovakia

Changes in the structure of small mammals’ communities (Eulipotyphla, Rodentia) along urban–rural gradient indicate the environmental state of stability or instability. Since small mammals are important with regard to the transmission of diseases to man and domestic animals, therefore knowledge of their association with the landscape structure is needed in land use planning. In course of the period from 2015 to 2017, there were recorded 109 individuals belonging to 15 species at 9 study sites (3 rural, 3 suburban, and 3 urban). We recorded a decrease in the average number of species in the direction of the suburban–urban–rural gradient. The number of individuals decreased in the rural–urban–suburban gradient. Eudominant species Clethrionomys glareolus (D = 20.2%), Microtus arvalis (13.8%), and Sorex araneus (19.3%) preferred the close links between the terms of the rural landscape, while Apodemus agrarius (D = 11.9%) and Sorex minutus (D = 11.0%) preferred the close links between the terms of the urban landscape.

Borrelia miyamotoi infection in Apodemus spp. mice populating an urban habitat (Warsaw, Poland)

The two of three species of city-inhabiting (Warsaw, Poland) Apodemus spp. mice were showed to be infected with Borrelia miyamotoi, spirochete bacterium considered to be a tick-borne relapsing fever (TBRF) disease causative agent. The pathogen infection was ascertained based on bacterium DNA presence in a blood (obtained from the lateral tail vein) of the mice, using the nested polymerase chain reaction (PCR) technique. The B. miyamotoi carriers populated not only green spaces situated in the suburban areas but also recreational parks and lawns in the city centre proper. Moreover, we found no significant differences in the infection rate depending on mouse species. The total prevalence of infection at the level of 5.6% suggests the potential role of urban-settled rodents in the spreading of the tick-borne zoonosis, which pose high risk to public health.

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First confirmation of Borrelia miyamotoi infection in urban rodents in Poland.

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The pathogen was found to infect city-inhabiting mice with a total prevalence of 5.6%.

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Degree of human pressure within habitat did not affect rodents' infection rate.

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Tick-borne zoonosis spread by mice could pose potential high risk to public health.

Changes in the social behavior of urban animals: more aggression or tolerance?

Behavioral traits play a major role in successful adaptation of wildlife to urban conditions. However, there are few studies showing how urban conditions affect the social behavior of urban animals during their direct encounters. It is generally believed that the higher density of urban populations translates into increased aggression between individuals. In this paper, using a camera-trap method, we compared the character of direct encounters in urban and non-urban populations of the striped field mouse Apodemus agrarius (Pallas, 1771), a species known as an urban adapter. We confirmed the thesis that urbanization affects the social behavior and urban and rural populations differ from each other. Urban animals are less likely to avoid close contact with each other and are more likely to show tolerant behavior. They also have a lower tendency towards monopolization of food resources. The behavior of urban animals varies depending on the time of day: in the daytime, animals are more vigilant and less tolerant than at night. Our results indicate that, in the case of the species studied, behavioral adaptation to urban life is based on increasing tolerance rather than aggression in social relations. However, the studied urban adapter retains the high plasticity of social behavior revealed even in the circadian cycle. The observation that tolerance rather than aggression may predominate in urban populations is a new finding, while most studies suggest an increase in aggression in urban animals. This opens an avenue for formulating new hypotheses regarding the social behavior of urban adapters.

On the Doorstep, Rodents in Homesteads and Kitchen Gardens

Scarcely investigated in terms of small mammals, kitchen gardens and homesteads form a subset of environments. Using results of snap trapping, we present the first data on small mammal species diversity, gender and age structure, relative abundance, body fitness, and reproduction parameters in these commensal habitats (kitchen gardens, homestead gardens, houses, and outbuildings). We expected that (i) house mice should be the dominant species in buildings, while striped field mice should be dominant in gardens, (ii) body condition should be the highest in buildings, (iii) body condition should increase in the autumn, irrespective of the habitat, and (iv) breeding failures in the form of disrupted pregnancies should be observed. Not all of the predictions were confirmed. From the seven recorded species, gardens and outbuildings were dominated by yellow-necked mice, while bank voles dominated in buildings where food was available. The number of recorded species and diversity index increased during the autumn months. The body condition was highest in rodents that were trapped in gardens. It decreased towards winter, with the exception of the striped field mouse. Breeding disturbances were recorded in all of the most numerous species, comprising 16.7-100% of all observed pregnancies.

Concentration of Mercury in the Livers of Small Terrestrial Rodents from Rural Areas in Poland

Small terrestrial mammals could be used as accumulative biomonitors of different environmental contaminants, but the knowledge of the level of Hg in their bodies is scant. The aim of our research was to verify the factors influencing Hg bioaccumulation and to analyze the concentration of total mercury (Hg) in the livers of four species of wild terrestrial rodents from different rural areas of Poland: the yellow-necked mouse (Apodemus flavicollis), striped field mouse (Apodemus agrarius), common vole (Microtus arvalis), and bank vole (Myodes glareolus). The concentration of total Hg was analyzed in liver tissue by atomic absorption spectrometry using a direct mercury analyzer. The concentration of Hg found in the livers of rodents ranged from <1 to 36.4 µg/kg of wet weight, differed between study sites, species, and sexes, and was related to body weight. We addressed feeding habits as potential causes of differences in liver Hg concentration among species.

Urban green area provides refuge for native small mammal biodiversity in a rapidly expanding city in Ghana

Urbanization is a key driver of global biodiversity loss. Although sub-Saharan African countries are experiencing unprecedented urbanization and urban expansion, very little is known about how this impacts tropical biodiversity. Here, we assessed the effects of urban expansion and urban green space on local small mammal species diversity in Accra, Ghana. We surveyed small mammals in the University of Ghana botanical garden, an urban green area (UGA) and adjoining built-up environment (BE) and compared the results with baseline data (BLD) collected when large areas of the current city still remained mostly undeveloped. The methodology involved live-trapping using Sherman collapsible live-traps. Our data showed higher small mammal abundance and diversity in the UGA than BE. Similarity of species composition was higher between UGA and BLD than between BE and BLD. The small mammal species captured in BE (the rodents Mastomys erythroleucus, Rattus rattus, and Arvicanthis rufinus, and the shrew Crocidura olivieri) are known to easily adapt to human-modified landscapes. Our results suggest that urbanization negatively influenced the abundance, diversity, and community composition of small mammals. Efforts should be directed towards the integration of urban green areas into urban land development planning in developing countries in order to conserve local wildlife and ecological services that enhance the quality of urban life.

Urban rodent reservoirs of Borrelia spp. in Warsaw, Poland

The anticipated worldwide surge in urban environments is generating ever-greater interest in the study of host-pathogen interactions in this specific type of habitat. We investigated the potential of city-inhabiting rodents to serve as the main Lyme borreliosis agents (Borrelia spp.) reservoir. We also tried to verify if anthropogenic disturbances changing the vertebrate species community composition may also alter the scheme of Borrelia spp. circulation. A total of 252 Apodemus mice (A. agrarius, A. flavicollis, A. sylvaticus) were captured in Warsaw (Poland), at sites classified into different zones of anthropogenic disturbance, ranging from suburban forests to municipal parks strictly in the city centre. Borrelia spp. infection, ascertained based on bacterium DNA presence in the rodents' blood, was found only in A. agrarius and A. flavicollis (7.6 and 6%, respectively). Only one species from the Borrelia genus - the mammal-associated species B. afzelii - was found in the mice studied. We found no statistical evidence of a correlation between infection in Apodemus mice and the zone of anthropogenic disturbance where the mice were caught. Non-homogeneous concentrations of Borelia spp. infected specimens within the strict city centre area suggest a lack of contact between members of particular mice subpopulations, and their responsibility for relatively high, but local Borrelia spp. infection.

Comparison of helminth community of Apodemus agrarius and Apodemus flavicollis between urban and suburban populations of mice

The growing human population and the development of urban areas have led to fragmentation and destruction of many natural habitats but have also created new urban habitats. These environmental changes have had a negative impact on many species of plants and animals, including parasite communities. The aim of present study was to compare the helminth communities of Apodemus flavicollis and Apodemus agrarius in natural and urban habitats. Helminth burdens were assessed in 124 mice, 48 A. flavicollis, and 76 A. agrarius from two managed forests close to the city boundaries and two city parks within Warsaw, Central Poland. In total, eight species of helminths, Nematoda (n = 3), Digenea (n = 2), and Cestoda (n = 3), were identified. Helminth community structure and prevalence/abundance of individual helminth species differed significantly between the two Apodemus species. Overall, prevalence and abundance of helminth species were significantly higher in A. agrarius compared to A. flavicollis. For A. flavicollis, higher prevalence and abundance of helminths were detected in individuals from managed forest habitats in comparison to city parks. In striped field mice, much higher prevalence and mean abundance were recorded in rodents trapped in city parks than in managed forests. This phenomenon may be explained by better adaptation of A. agrarius, compared to A. flavicollis, to city habitats, resulting in high local densities of mice and the full range of parasite species affecting this host species. Our data confirm also that the established routes of infection exist for selected helminth species in the urban environment.