Article

COMMENSAL RODENT CONTROL: CHALLENGES FOR THE NEW MILLENNIUM

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Abstract

Predictions for world human population trends predict exponential growth. The close relationship be- tween commensal rodents and human populations suggests that the commensal rodent population may also increase exponentially, perhaps most dramatically in those areas which are least able to cope. The paper identifies a number of challenges relating to both the need for further research and development of effective control techniques and the co-ordination and application of the results of this research on a world wide basis. The need for effective identification of the cost benefits of control is identified as a catalyst for the development of more effective rodent control strategies.

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... (4) What is the way forward? Importantly, because we found that these expectations and others have been summarized and synthesized in other detailed reviews, opinion pieces, and book chapters (Davis and Jackson, 1981;Kaukeinen, 1994;Colvin and Jackson, 1999;Meyer, 1999;Corrigan, 2006) we focused this review primarily on whether those expectations have been achieved. We synthesized this information with a view toward identifying options to improve the field of municipal rat management. ...
... Chief among these was a shared expectation that, to achieve long-term reductions in infestations at a municipal scale, management initiatives needed to address rats and FWAH everywhere that they existed on a regular, ongoing, and comprehensive basis. Authors agreed that failing to meet any of those expectations would allow rat populations to quickly return to pre-control levels due to their high fecundity and ability to move around cities (Davis, 1953;Drummond, 1970;Colvin et al., 1990;Meyer, 1999;Corrigan, 2006;de Masi et al., 2009). This expectation was grounded in studies which found that infestations rebounded when management programs were short-term (Barnett, 1947), when they were unable to address a rat problem on a specific property (Lambropoulos et al., 1999), and when FWAH conditions were not sustainably or completely addressed (Fernández et al., 2007). ...
... Experts expressed anecdotal dissatisfaction with the overall effectiveness of municipal management approaches (Sherrard, 1943;Davis, 1952;Margulis, 1977;Davis and Jackson, 1981;Kaukeinen, 1994;Colvin and Jackson, 1999;Lambropoulos et al., 1999;Meyer, 1999Meyer, , 2003Easterbrook et al., 2005;Parsons et al., 2017;Himsworth, 2020). It appeared, based on authors descriptions, that municipal approaches failed to sustainably reduce infestations (i.e., the outcome expectations), not because there was a flaw in the long-held rat-reduction paradigm, but because cities did not adhere to a variety of methodological and attribute expectations. ...
Article
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To sustainably control urban rat infestations, management efforts need to encompass large areas of urban centers. Therefore, the objective of this review and narrative synthesis was to collate what is known about municipal-scale rat management. We explored the management frameworks that have been used at a large scale in cities and we describe the expectations of experts who have designed and implemented these frameworks. We found that there has been a persistent "war on rats" paradigm driving this literature since the early 1900s. Not only was there little quantitative evidence to support this paradigm and associated methodologies, but together, they failed to meet the expectations of those who designed and implemented them due to real-world constraints (i.e., limited resources). To improve the field of municipal management, we identify two distinct options. First, stakeholders may continue to wage the "war on rats" while improving existing strategies within this paradigm. Key pathways forward include developing evaluation metrics aligned with program objectives, establishing the cost-effectiveness of methodologies, and improving control efficacy. Second, we suggest a new paradigm, one that considers that rat management is a complex system that must be approached by first mapping its complexity to highlight and prioritize the many complex upstream determinants of infestations. This perspective highlights how rat management may be a wicked problem for which there is no overarching solution and instead can only be managed by making incremental gains in individual components of the problem over time. Importantly, we propose an alternative management objective that places a priority on improving the overall health of the community, instead of on eliminating rats, and we stress that management goals must address stakeholders' goals as their investment is essential for a sustained program.
... Studies that have reported on the effectiveness of municipal-scale management initiatives have lamented that these approaches are often unsuccessful (Sherrard 1943;Margulis 1977;Colvin and Jackson 1999;Meyer 2003;Parsons et al. 2017). Failures have been attributed to a variety of causes including time-limited initiatives (Sherrard 1943), insufficient funding and resources (Kaukeinen 1994;Brown and Laco 2015), a focus on reacting to citizen complaints (Margulis 1977;Meyer 2003), insufficient political or public interest (Davis 1952;Colvin and Jackson 1999) and barriers to coordinating efforts across the urban landscape (Meyer 1999). ...
... Studies that have reported on the effectiveness of municipal-scale management initiatives have lamented that these approaches are often unsuccessful (Sherrard 1943;Margulis 1977;Colvin and Jackson 1999;Meyer 2003;Parsons et al. 2017). Failures have been attributed to a variety of causes including time-limited initiatives (Sherrard 1943), insufficient funding and resources (Kaukeinen 1994;Brown and Laco 2015), a focus on reacting to citizen complaints (Margulis 1977;Meyer 2003), insufficient political or public interest (Davis 1952;Colvin and Jackson 1999) and barriers to coordinating efforts across the urban landscape (Meyer 1999). However, due to an overall paucity of research evaluating existing municipal programs, the full breadth and relative significance of potential strengths, weaknesses, barriers and opportunities associated with different municipal rat management strategies remain unclear. ...
... Studies that have reported on the effectiveness of municipal-scale management initiatives have lamented that these approaches are often unsuccessful (Sherrard 1943;Margulis 1977;Colvin and Jackson 1999;Meyer 2003;Parsons et al. 2017). Failures have been attributed to a variety of causes including time-limited initiatives (Sherrard 1943), insufficient funding and resources (Kaukeinen 1994;Brown and Laco 2015), a focus on reacting to citizen complaints (Margulis 1977;Meyer 2003), insufficient political or public interest (Davis 1952;Colvin and Jackson 1999) and barriers to coordinating efforts across the urban landscape (Meyer 1999). However, due to an overall paucity of research evaluating existing municipal programs, the full breadth and relative significance of potential strengths, weaknesses, barriers and opportunities associated with different municipal rat management strategies remain unclear. ...
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Rats evoke public health and economic concern in cities globally. Rapid urbanization exacerbates pre-existing rat problems, requiring the development and adoption of more effective methods of prevention, monitoring and mitigation. While previous studies have indicated that city-wide municipal management approaches often fail, such outcomes are often left without specific explanation. To determine how municipalities could more effectively develop and implement large-scale approaches, we interviewed stakeholders in municipal rat management programs to document their opinions, recommendations and the challenges they face. Using a thematic framework method, this study collates and analyzes in-depth interviews with 39 stakeholders from seven cities across the United States. Overall, stakeholders' recommendations for municipal rat management aligned with many conceptual attributes of effective management reported in the literature. Specifically, stakeholders highlighted the need to prioritize the reduction of resources available to sustain rat infestations (e.g. food, water and harborage), to focus on proactive (vs. reactive) measures, and to implement large-scale data collection to increase the efficiency of cross-city rat control. Stakeholders also suggested novel approaches to management, such as mitigating rat-associated risks for vulnerable populations specifically and developing tailored initiatives based on the specific needs and desires of residents. We synthesize these recommendations in light of reported barriers, such as resource limitations, and consider several opportunities that may help municipalities reconceptualize their approaches to city-wide rat management.
... The Norway rat Rattus norvegicus (Rodentia: Muridae, Berkenhout 1769) is a highly invasive species worldwide (Long, 2003), and as with other invasive rodents, it can cause major concerns for human health (Epstein, 1995;Meerburg et al., 2009a;Mills and Childs, 1998), agricultural crop damage (Meerburg et al., 2009b;Meyer, 1999;Stenseth et al., 2003) and natural ecosystems (Atkinson, 1978;Campbell, 1978;Ramsay, 1978;Simberloff, 2009;St Clair, 2011). To eradicate and control invasive and pest rodents, considerable resources are invested annually by governmental and non-governmental agencies (Coomes et al., 2006;Dilks and Towns, 2002;Meerburg et al., 2009b;Meyer, 1999;Stenseth et al., 2003). ...
... The Norway rat Rattus norvegicus (Rodentia: Muridae, Berkenhout 1769) is a highly invasive species worldwide (Long, 2003), and as with other invasive rodents, it can cause major concerns for human health (Epstein, 1995;Meerburg et al., 2009a;Mills and Childs, 1998), agricultural crop damage (Meerburg et al., 2009b;Meyer, 1999;Stenseth et al., 2003) and natural ecosystems (Atkinson, 1978;Campbell, 1978;Ramsay, 1978;Simberloff, 2009;St Clair, 2011). To eradicate and control invasive and pest rodents, considerable resources are invested annually by governmental and non-governmental agencies (Coomes et al., 2006;Dilks and Towns, 2002;Meerburg et al., 2009b;Meyer, 1999;Stenseth et al., 2003). ...
Article
We tested whether conspecific attraction can be more efficient than food bait for the detection and capture of an invasive, social species, the Norway rat Rattus norvegicus. We compared trapping rates between male and female laboratory rats and food baited controls at four mainland sites with low rat population densities, three recreational sites (Zoos) with an abundance of food in the environment, and in manipulated island rat incursions. Live lures were more efficient than food baits at both the mainland and recreational sites. There were no differences between the attractiveness of lure animals based on gender either of the lure or of the captured animals. In the manipulated rat incursions, where radio collared male rats were released on a rat free island, two animals were caught with female lures, and the third lost its collar and evaded detection. In the current study we advocate that animal behavior can help inform and guide innovative tools for the control and management of invasive species. We show that laboratory rats might be efficient as lures for their wild counterparts. Furthermore, our results emphasize the need for a flexible and varied rat control toolbox. We suggest that the use of laboratory rats should be considered in future control management plans for invasive Norway rats.
... Although many municipalities have enacted citywide management initiatives, previous literature has indicated that many of these approaches have not been able to demonstrate a sustainable reduction in the number of rats (Lee et al., 2022). While the reasons for these reported failures are unclear, authors have suggested that this may be due to a lack of resources (Kaukeinen, 1994;Wirth & Brown, 2015), a lack of interest or prioritization by relevant stakeholders (Colvin & Jackson, 1999;Davis, 1952), an inability to account for the complexity of rat management (Davis & Jackson, 1981;Meyer, 1999), and difficulties in changing residents' behaviors contributing to rats (Fall & Jackson, 1998;Lambropoulos et al., 1999). ...
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While literature indicates that municipal rat management approaches are often unsuccessful, a lack of research comparing strategies makes the breadth of opportunities and challenges associated with different approaches uncertain. Here, we explored the municipal rat management policies and programs in seven cities in the United States of America. Rat policies were attained by collecting rat management-related municipal codes in each city. Information on rat programs was obtained through interviewing program stakeholders. Analysis followed a qualitative framework method to identify and describe themes associated with the structure and function of management approaches. Municipal codes served as a foundation for municipalities by outlining when, where, how, and by whom rat problems should be addressed. Programs employed the primary people responsible for performing on-the-ground management and they acted as a municipal "brain," organizing the city's strategy. We identify opportunities and barriers for other municipalities to consider in the design of their own rat management strategies.
... Invasive rodents are pests worldwide (Long, 2003) and cause major concerns to human health (Epstein, 1995;Mills and Childs, 1998;Meerburg et al., 2009a), agricultural crop damage (Meyer, 1999;Stenseth et al., 2003;Meerburg et al., 2009b) and natural ecosystems (Atkinson, fast re-establishment of populations from even very few survivors or new invaders (Ruscoe, 2001;Goldwater, 2007;Howald et al., 2007;MacKay et al., 2007). Therefore, longterm control programs to keep populations at a minimum are required. ...
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Invasive rodents pose major concerns for human health, agriculture and conservation. House mice Mus musculus are one of the most formidable invasive rodents, and require intensive efforts for their control. Control measures rely largely on food baits but difficulties in the eradication of mouse populations necessitates the development of alternative pest control methods. Conspecific attraction is used as a luring method for invasive species control and can be used to attract wild mice into traps. The proximate cause of the live lure attraction might be primarily scent or a more complex array of stimuli emanating from a live animal. We used a Y maze apparatus to test the effect of urine from mice fed high vs. low protein diets on the attraction of male and female conspecific wild mice (focal animals), and tested whether the protein content of the diet of focal animals affected their response. We further compared the strength of attraction of wild mice toward wild and laboratory (Swiss Webster) live lure conspecifics of the opposite sex. Both males and females were marginally more attracted to conspecific scent originating from lure animals previously on high protein diets, regardless of the focal animal's diet. Wild mice were equally attracted to laboratory mice of the Swiss Webster strain and wild mice. However, preference for one side of the maze was significant. Males were more attracted to female lures than females were to male lures. Activity of both sexes near conspecifics was significantly reduced over exposure time. We discuss the implications of these findings for the control of invasive mice.
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