The secret life of the city rat: a review of the ecology of urban Norway and black rats (Rattus norvegicus and Rattus rattus)

Norway rats (Rattus norvegicus) and black rats (Rattus rattus) are among the most prolific and widespread urban pest species in the world. Yet despite their ubiquity, a unified understanding of the ecology of these species in urban habitats eludes us. A comprehensive understanding of urban rat ecology is important for managing rat populations and mitigating the harmful effects that they may have on urban ecosystems (e.g., structural damage, food contamination, and disease spread). The objective of this systematic review and narrative synthesis is to collate, compare, and contrast data from the published literature regarding the ecology of Norway and black rats in urban centers. Themes emerging from the synthesis process, and discussed in detail, include population dynamics, behavior, movement, and environmental influences on rat populations.     

Brown rats (<Emphasis Type="Italic">Rattus norvegicus</Emphasis>) in urban ecosystems: are the constraints related to fieldwork a limit to their study?

Nowadays, the majority of human beings live in urban ecosystems, with this proportion expected to continue increasing in the future. With the growing importance of urban rat-associated issues (e.g. damages to urban infrastructures, costs of rat-control programs, rat-associated health risks), it is becoming indispensable to fill the identified gaps in knowledge on the urban brown rat regarding, among others, its density, home range, genetic structure, and infectious status. In this context, live-trapping is a crucial prerequisite to any scientific investigation. This paper assesses the main constraints and challenges regarding the urban field and describes the major steps to be considered when planning research on urban rats. The primary challenges are i) the characterization of the urban experimental unit; ii) the choice of a trapping design: the use of live-trapping in capture-mark-recapture design, in association with modern statistics, is highly recommended to answer ecological questions (although these methods, mostly developed in natural ecosystems, need to be implemented for the urban field); iii) the potential ethical considerations with regard to animal welfare and field-worker safety; iv) the building of mutually-beneficial collaborations with city stakeholders, pest control professionals, and citizens. Emphasis must be put on communication to the public and education of field-workers. One major need of modern urban rat research is a peer-validated field methodology allowing reproducibility, repeatability, and inference from urban field studies and enabling researchers to answer long-standing key questions about urban rat ecology.     

A comparative assessment of track plates to quantify fine scale variations in the relative abundance of Norway rats in urban slums

Norway rats (Rattus norvegicus) living in urban environments are a critical public health and economic problem, particularly in urban slums where residents are at a higher risk for rat borne diseases, yet convenient methods to quantitatively assess population sizes are lacking. We evaluated track plates as a method to determine rat distribution and relative abundance in a complex urban slum environment by correlating the presence and intensity of rat-specific marks on track plates with findings from rat infestation surveys and trapping of rats to population exhaustion. To integrate the zero-inflated track plate data we developed a two-component mixture model with one binary and one censored continuous component. Track plate mark-intensity was highly correlated with signs of rodent infestation (all coefficients between 0.61 and 0.79 and all p-values?<?0.05). Moreover, the mean level of pre-trapping rat-mark intensity on plates was significantly associated with the number of rats captured subsequently (Odds ratio1.38; 95 % CI 1.19–1.61) and declined significantly following trapping (Odds ratio 0.86; 95 % CI 0.78–0.95). Track plates provided robust proxy measurements of rat abundance and distribution and detected rat presence even when populations appeared ‘trapped out’. Tracking plates are relatively easy and inexpensive methods that can be used to intensively sample settings such as urban slums, where traditional trapping or mark-recapture studies are impossible to implement, and therefore the results can inform and assess the impact of targeted urban rodent control campaigns.     

Foxes and foxhunting on farms in Wiltshire: a case study

A questionnaire survey of 220 farmers, and interviews with 13 Masters of packs of foxhounds, in the county of Wiltshire, UK, were undertaken to answer questions on whether farmers perceived the red fox, Vulpes vulpes, to be a pest, and on pest control methods. Farmers’ opinions regarding the need for fox control were often contradictory and not directly governed by their own interests. Although two-thirds did not consider the fox to be a personal pest, most believed that foxes should be controlled everywhere, because they were too numerous. Far fewer believed foxes responsible for actually taking domestic livestock. Where farmers’ opinions of the fox were influenced by personal stock loss, their main concern was chickens, which were generally kept on a non-commercial scale. The evidence is that, over the whole county, hunting with hounds makes an insignificant contribution (5%) to total mortality (through `control efforts'), most being shot. A greater density of foxes was reported shot when there was a perceived pest problem, where lamb or gamebird losses were reported, or when a farmer farmed stock. Where the farmer considered shooting to be effective or humane, a greater density of foxes was also shot. The Hunt was less responsive to these situations, paying fewer visits to farms where the fox was considered a pest, or where the farmer welcomed the Hunt, hunting being more likely to occur on farms reporting fewer foxes, less livestock farming and fewer fox pest problems. It is likely that these farms presented fewer incompatibilities with, or physical access problems for, the Hunt. Most farmers, even on farms where foxes were considered a pest, tolerated, rather than encouraged, hunting on their land. Evidence from hunting farmers suggests that hunting is considered primarily as recreation, and secondarily as a method of controlling foxes.     

Black widow spiders in an urban desert: Population variation in an arthropod pest across metropolitan Phoenix, AZ

The effects of urban disturbance are critical to understand, as the majority of the world??s population now resides in urban centers. For example, urbanization often leads to reduced species diversity at the expense of a few urban-adapted taxa. However, it remains unclear why some taxa thrive following human disturbance whereas others do poorly. The western black widow spider, Latrodectus hesperus, thrives in disturbed, urban habitat??often forming dense aggregations (i.e., infestations) relative to typical low-density, desert populations. We examined the population dynamics of ten black widow aggregations spread across metropolitan Phoenix, AZ, during the peak of the breeding season (June?CAugust). Here we show that prey abundance, female mass, web volume and population density exhibit minimal temporal variation across the breeding season, but that prey abundance, female mass and population density show significant spatial variation across the ten urban aggregations. Our measure of prey abundance and foraging success, the number of prey carcasses found in black widow webs, shared a strong positive relationship with female mass and population density, but not with web volume. Surprisingly, female mass, web volume and population density were not correlated with each other. The abiotic variables we measured at each site did a poor job of explaining black widow population parameters, although we did find a marginal trend for more recent developments to harbor denser black widow aggregations. Our findings support the generalization that urbanization heightens spatial variation, and we suggest that local urban prey abundance is influential in promoting urban infestations full of heavy, fecund female black widows. Studies of the population ecology of urban pests are necessary to identify the mechanisms allowing some species to thrive following human disturbance while much native biodiversity is lost following urbanization.     

Records of rat control campaigns in a food market with the largest seafood trading volume worldwide

Urban Ecosystems - Brown rats (Rattus norvegicus) and roof rats (Rattus rattus) are among the most common mammals worldwide. Little is known about the effects of season on rat population size,...     

Improving confidence in tree species selection for challenging urban sites: a role for leaf turgor loss

High species diversity is argued to be the most important requisite for a resilient urban forest. In spite of this, there are many cities in the northern hemisphere that have very limited species diversity within their tree population. Consequently, there is an immense risk to urban canopy cover, if these over-used species succumb to serious pests or pathogens. Recognition of this should motivate the use of less commonly used species. Analysis of plant traits, such as the leaf water potential at turgor loss (Ψ_P0), can provide useful insights into a species’ capacity to grow in warm and dry urban environments. Therefore, the aim of this study was to evaluate Ψ_P0 of 45 tree species, the majority of which are rare in urban environments. To help evaluate the potential for using Ψ_P0 data to support future decision-making, a survey of professionals engaged with establishing trees in urban environments was also used to assess the relationship between the measured Ψ_P0 and the perceived drought tolerance of selected species. This study demonstrates that Ψ_P0 gives strong evidence for a species’ capacity to tolerate dry growing conditions and is a trait that varies substantially across species. Furthermore, Ψ_P0 was shown to closely relate to the experience of professionals involved in establishing trees in urban environments, thus providing evidence of its practical significance. Use of plant traits, such as Ψ_P0, should, therefore, give those specifying trees confidence to recommend non-traditional species for challenging urban environments.     

Local perception of rodent-associated problems in Sahelian urban areas: a survey in Niamey,Niger

Rodents are involved in the epidemiology of many pathogens and are major pests for agriculture. Local perception and beliefs about rodents and their damages is a key element of control programs. We here present the first survey focusing on the human perception of rodent-associated problems in an African town, namely Niamey, Niger. In total, 170 interviews were conducted in 18 different urban districts where rodents (Mastomys natalensis, Rattus rattus and Mus musculus) are widespread and abundant. Rodent-associated problems were mentioned in almost all instances (96.5 %). Eight different categories of rodent-induced nuisances could be recurrently identified. The most frequently cited one consists in damages on food and food stocks (63.1 %), followed by damages on houses (47.3 %), furniture (19.5 %) and clothes (16.8 %). There was no significant association between damages and districts, which means that the perception of rodent-associated problems did not vary significantly across the city. Our survey strongly suggests that rodents may represent major pests not only for farmers, but also for inhabitants of towns, thus contributing to reinforce economic vulnerability. Finally, no mention of sanitary or medical problems was ever recorded during our survey, thus pointing towards an apparent absence of knowledge about the potential role of rodents in some public health issues.     

Understanding and influencing urban residents’ knowledge about wildland management in Austin, Texas

Due to increasing exurban settlement around Austin, Texas and subsequent land use changes, the City of Austin Wildland Division faces competing pressures from residential communities regarding land and wildlife management actions. Current environmental education and outreach efforts in Austin focus on developing environmental literacy about the city’s wildland areas adjacent to exurban settlement as well as their management program. The desired outcome is to promote more positive perceptions and motivate pro-environmental behaviors that are consistent with the city’s wildland program. We conducted a mail survey of 1,000 residents living near the urban wildlands to better understand factors that influence residents’ proficiency in four knowledge domains: karst aquifers, endangered species, rangeland ecology, and the city’s management program. Regression analyses identified positive associations between local newspaper readership and residents’ environmental knowledge of karst aquifer geology, rangelands, and city’s wildland program. Previous engagement in environmentally oriented education programs or organization was positively associated with all four knowledge domains. Some strategies for information dissemination about the wildlands include the use of local newspapers and homeowners association newsletters. Newer, younger residents are the suggested target audience for initiating a proposed environmental education and outreach program. Such programs should incorporate both local environmental organizations and homeowners associations.     

Tales of urban conservation: <Emphasis Type="Italic">Eumaeus</Emphasis> butterflies and their threatened cycad hostplants

Urbanization has caused the local extinction of several butterfly species around the world, while others have managed to thrive in urban areas. Butterflies of the genus Eumaeus are among the most striking and colorful lycaenid butterflies in the Americas, but their neurotoxic hostplants, cycads, are a highly threatened plant group. The main threats for cycads are the loss and modification of their habitats and their removal for ornamental purposes, which in addition to their slow growth rate, make them highly vulnerable. Ornamental cycads are taken from natural habitats to urban areas, where they are playing an important role for Eumaeus reproduction. We here report two cases in which two Eumaeus species (E. childrenae, E. atala) are following and utilizing ornamental cycads to reproduce in urban areas, showing how significant urban areas can be, ecologically speaking. Aside from having enormous potential as flagship species for conservation in urban areas, these butterfly and plant species, and their interactions, shed encouraging light on the idea of putting reconciliation ecology ideas into action.     

The impact of urbanisation on avian species: The inextricable link between people and birds

This study investigates the impact of urbanisation on birdlife in a major city. Line transects and point counts were used to survey birds in three habitat types: parkland, residential areas and business/industrial areas. Abundance, richness and diversity of assemblages were determined for all bird species and for those birds native to the area. Behaviours of birds, and of human residents in relation to birds, in these urban areas were documented, including all instances of avian aggression. Bird species, including a subset of native bird species, have greater abundance and richness in parklands. Overall species diversity is greatest in residential habitat types, but native diversity is greatest in parklands. Introduced species are most abundant in business/industrial habitat types. The most frequent aggressive encounters were initiated by noisy miners Manorina melanocephalas, one of the four most common species throughout all habitat types (other common species include the rainbow lorikeet Trichoglossus haematodus, rock dove Columba livia and common myna Sturnus tristis). Other behaviours involved birds utilising food and roost resources and were classified as being caused by active and passive human behaviours. These outcomes indicate that local changes to the environment can impact the bird species by providing different food and roost resources. Human residents and local governments have a range of tools to modify the diversity of urban areas. Further research is needed to determine alternative definitions of modification, such as defining it as open space, and investigating the health of the avian populations in urban areas.     

Peeking into the past to plan the future: Assessing bird species richness in a neotropical city

Urbanization has been considered as a major threat to biodiversity, making its ecology of increasing interest. Many urban ecology studies have been developed in a short time-scale, measuring real-time patterns. However, long-term studies are imperative to understand the responses of some species to the urbanization process. In this study, we aimed to assess the information provided by a recent one-year citywide bird survey when compared to a published ‘historical’ bird list of a neotropical city (Xalapa, Mexico) that compiles information of the past three decades, mainly from urban greenspaces. Specifically, we contrasted species richness values and assessed differences in species composition between both lists. We recorded 51 species in the one-year citywide survey, representing ~15 % of those reported in the historical list. Nonetheless, the upper-bound confidence interval of the citywide survey richness prediction represented ~66 %. Most of the species recorded in the one-year citywide survey are insectivores and granivores, a pattern that agrees with previous findings that underline the importance of insectivores as part of urban bird communities in the Neotropics. Although we used robust methods to compare our one-year citywide bird list and the historical list for the city of Xalapa, we acknowledge the limitations of comparing them. However, our results shed some light on the kind and type of information that one-year citywide surveys can provide and the importance of long-term studies for comprehending the processes involved in biodiversity changes within urban areas over time. Undoubtedly, establishing long-term citywide surveys sampling birds and other biodiversity groups will allow us to better understand the response of biodiversity to urbanization over time.     

Urban resident attitudes toward rodents,rodent control products,and environmental effects

Rodent control in urban areas can result in the inadvertent mortality of non-target species (e.g., bobcats). However, there is little detailed information from urban residents about rodent control practices. We evaluated urban rodent control behaviors in two areas of California (southwestern Bakersfield and in proximity to Santa Monica Mountains National Recreation Area (SAMO)) where biologists have observed non-target mortality among carnivores resulting from exposure to anticoagulant rodenticides. Using a mail survey instrument, we asked residents about rodent control practices including products used and application, attitudes toward rodents, and concern about non-target mortality. Forty-one percent of Bakersfield (response rate = 20%) and 59% of SAMO (response rate = 31%) respondents reported rodent or other animal control on their property. Snap traps and anticoagulants were the most commonly used physical and chemical control products, respectively. Many respondents were unsure whether (12% Bakersfield; 17% SAMO) or which (39% Bakersfield; 46% SAMO) chemical products were used on their property. When told of possible non-target effects, a majority of respondents were either very or somewhat concerned. Attitudes toward rodents were relatively negative across all respondents. Respondents who applied control products themselves (as opposed to a third party) were most supportive of ensuring availability of rodent control products. Our results suggest that residents do not readily connect their personal or household activities with larger environmental effects, and highlight potential focal areas for policy evaluation related to wildlife management, such as providing explicit information about potential environmental effects of rodent control products.     

Habitat structure: A fundamental concept and framework for urban soil ecology

Habitat structure is defined as the composition and arrangement of physical matter at a location. Although habitat structure is the physical template underlying ecological patterns and processes, the concept is relatively unappreciated and underdeveloped in ecology. However, it provides a fundamental concept for urban ecology because human activities in urban ecosystems are often targeted toward management of habitat structure. In addition, the concept emphasizes the fine-scale, on-the-ground perspective needed in the study of urban soil ecology. To illustrate this, urban soil ecology research is summarized from the perspective of habitat structure effects. Among the key conclusions emerging from the literature review are: (1) habitat structure provides a unifying theme for multivariate research about urban soil ecology; (2) heterogeneous urban habitat structures influence soil ecological variables in different ways; (3) more research is needed to understand relationships among sociological variables, habitat structure patterns and urban soil ecology. To stimulate urban soil ecology research, a conceptual framework is presented to show the direct and indirect relationships among habitat structure and ecological variables. Because habitat structure serves as a physical link between sociocultural and ecological systems, it can be used as a focus for interdisciplinary and applied research (e.g., pest management) about the multiple, interactive effects of urbanization on the ecology of soils.     

Urbanization and the abundance and diversity of Prairie bats

The effects of urbanization on biodiversity are generally considered to be negative, but the potential for landscape context to modulate these effects has not been adequately examined because most urban ecology research has been conducted in one biome: the temperate forest. This bias also applies to studies of the urban ecology of bats, whose diversity is correlated with habitat heterogeneity. We investigated the hypothesis that in the fairly flat, homogeneous Prairies, urbanization, by creating structurally complex islands, benefits bats by increasing access to the vertical landscape elements (buildings and trees) in which they roost. From 2006 to 2008, we surveyed bat assemblages in and around Calgary, Alberta, using mist nets to capture them and bat detectors to record their echolocation activity. Our data supported the prediction that urbanization increases the abundance of Prairie bats, but not the prediction that it increases their diversity. Instead, the urban bat assemblage was less diverse, and exhibited decreased species evenness compared to non-urban assemblages. Although Myotis lucifugus dominated bat assemblages throughout our study area, this was most evident in the city, and this species drove the increased urban abundance of bats. Ultimately, we reject our hypothesis and conclude that urbanization in the Prairies may create attractive habitat for one synanthropic bat, but is detrimental to others.     

Demographic drivers of Norway rat populations from urban slums in Brazil

Urban Ecosystems - The Norway rat is a globally distributed pest, known for its resilience to eradication and control programs. Efficient population control, especially in urban settings, is...     

Urban forest and environmental inequality in Campos dos Goytacazes,Rio de Janeiro,Brazil

Social and spatial inequality regarding environmental resources and services is one of most complex issues affecting contemporary urban life. The objective of this research is to study the spatial distribution of trees in public areas in Campos dos Goytacazes, Rio de Janeiro, Brazil. This research presents data gathered in ten neighborhoods in Campos. These neighborhoods were split into three distinct groups using wealth levels. Data obtained include the number of trees and private gardens and tree species diversity per neighborhood street. Our results demonstrate that the wealthier neighborhoods have both the highest tree biodiversity and number of trees. In contrast, the poorer neighborhoods present a low biodiversity level and fewer tree species. Our results also showed that age of the neighborhoods was not a factor in explaining the number of trees in public spaces. Socioeconomic and education levels of the population seem to play a more causal on tree quantity and species diversity. This inequality stresses a problem with environmental justice, a characteristic of Brazilian cities intrinsically connected to urban sustainability.     

Spatial and genetic distribution of a north American termite, <Emphasis Type="Italic">Reticulitermes flavipes</Emphasis>, across the landscape of Paris

Urbanization often negatively impacts biological diversity. Some organisms, however, have traits that are preadapted to urban environments and thus may thrive. Reticulitermes flavipes is one such organism. Indigenous to the Eastern US, it has been introduced into multiple countries. In France, R. flavipes causes major damage to buildings. Although Paris is one of the country’s most infested cities, the factors determining R. flavipes’ distribution and propagation are poorly understood. Using data on termite occurrence, termite genetics, and environmental variables, our study aims to identify factors that explain the distribution and spread of R. flavipes within Paris. First, we explored the association between several environmental variables and the termite’s distribution pattern in Paris; since 2000, a total of 2106 infestations have been recorded. Second, we inferred termite population and colony genetic structure at 66 sample locations using 9 microsatellite loci. Third, we used least-cost models and partial Mantel tests to study the effects of environmental variables on the termite’s population genetic structure. Our analyses revealed that building-related variables were significantly associated with termite infestations and could thus help explain the termite’s spatial distribution pattern. Furthermore, railway networks also explain termite propagation and genetic patterns. Additionally, we found that the termite’s spread is likely driven by budding dispersal, which may be constrained by buildings and roads. Even if budding dispersal could facilitate R. flavipes’ spread in urban areas, it cannot explain the termite’s distribution in Paris all on its own. Indeed, termite propagation seems to be significantly driven by anthropogenic activities.     

Corporate lobbying: Role perceptions and perceived influence on political decisions of public affairs professionals

This study aims to provide insight into public affairs professionals’ role conceptions and perceived influence on political decision making. We conducted a quantitative online survey with 238 corporate public affairs professionals in Germany who worked either “in-house” at a corporation, for an industry association, or in a public affairs consultancy firm. Based on their main stakeholder orientation (clients, political actors, or society) and primary objectives (mediator, expert, or advocate), a cluster analysis categorized the professionals into four main roles: persuaders, advisors, coordinators, and mediators. Although acting in line with ethical norms and being transparent about their practices were deemed important for all roles, there were differences regarding the balancing of positions and loyalty toward the client. Finally, a regression analysis showed that financial resources, information sovereignty, and ethical considerations were the strongest predictors of public affairs professionals’ perceived influence on political decisions. Implications and avenues for future research are discussed.