Course:CONS200/2024WT1/The infestation of rats in Vancouver: Key threats and possible solutions

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Introduction

Rats infest areas with accessible food, water, and shelter, thriving in cluttered or unsanitary conditions.

Vancouver currently deals with a significant rat infestation problem that has become much more prominent in recent years. Research suggests this increase in rat infestations could be due to easy access to exposed garages, abandoned builds, and compost. The severity and frequency of rat infestations fluctuates seasonally, with research showing rates are higher during warmer seasons. In addition, the prevalence of rat infestations ranks high in residential and commercial areas that handle food.[1]

Factors contributing to Vancouver’s Rat Infestation

Vancouver’s moist and mild climate allows rats to thrive year round.[2]

Vancouver’s rat infestation is tied to a variety of possible causes, all likely working together to create and worsen the issue. While there are major causes related to both city planning and human behaviour, it is also important to consider the factors worsening the infestation and preventing its resolution. Rats are already in a position to thrive in the city, given Vancouver’s year round moist and mild climate, paired with large amounts of foliage amidst its dense urbanization.[2][3] This, along with ongoing waste management issues and environmental problems such as rodenticide usage and climate change, come together to create Vancouver’s rat infestation.[4][5]

British Columbia’s 2021 Ban on Anticoagulant Rodenticides

The most notable and widely believed origin of the infestation is British Columbia’s decision to ban certain types of anticoagulant rodenticides in January 2021.[5] The passing of this ban—while beneficial to predators of rats, such as owls and hawks that can die from the poison after eating afflicted rats—has resulted in a large increase of rat populations throughout both the city of Vancouver and the province as a whole.[5] Alternative control measures, such as trapping or exclusion methods, often fail to keep pace with the rodents’ rapid reproduction rates.[5]

Urban Layout and Vegetation

Rats and other rodents will use vegetation for nesting and hiding.[3]

Rats are extremely attracted to open food, waste, and moisture such as exposed garbage, abandoned buildings, compost, and residential and commercial areas that deal with food and water.[1] Rats are also likely to live around shrubbery and other small crevices and possible hiding spots that people are unable to reach.[3] This means that dense urban regions—such as the Vancouver Metropolitan Area—are particularly subject to thriving rat populations. Vancouver’s urban design and layout unintentionally supports rat populations, with a mix of densely populated neighbourhoods and lush green spaces. Rats also establish nests in shrubbery, parks, and other concealed areas, which offer both food and protection.[3] The proximity of these spaces to urban infrastructure creates easy pathways for rats to access homes, businesses, and waste sites.

Litter and Food Waste

Food waste provides rats with their primary food source in urban environments.[1]

Rats thrive on human-generated waste, particularly food waste, which offers them an abundant and consistent supply of nutrients in urban areas, enabling their rapid reproduction and population growth.[1] In a 2022 report, the City of Vancouver was determined to have the majority of large litter throughout the city be related to food and drink packaging and consumption, such as cups, cans, containers, and bags.[4] It is also reported that in 2022, large litter amounts have seen a decrease since peaking in 2020, although the city saw a 5% increase in average number of large litter per site compared to 2021, highlighting ongoing waste management issues in the city.[4]

Climate Change

Warmer weather also contributes to an increase in the rat population, as rats living in warm environments such as indoors, or outdoors during the summer, will breed year round.[2] Climate change has undoubtedly worsened the rat infestation in Vancouver, with longer and hotter summers allowing rats to breed at a higher rate.[2]

A Harsh Feedback Loop

These factors come together to create an unfortunate feedback loop that sustains Vancouver’s rat ongoing infestation. The city’s unique combination of densely populated urban areas interspersed with expansive green spaces offers an ideal environment for rats to thrive [3]. These green spaces serve as natural shelters, while urban infrastructure often provides additional hiding spots and nesting areas [3]. Moreover, improperly managed waste systems exacerbate the problem by supplying a consistent and readily available food source for the rodent population [1][3]. Climate change further accelerates the problem by extending breeding seasons, and recent legal reforms aimed at reducing the environmental and ethical impacts of pest control have inadvertently limited the use of certain traditional methods, such as rodenticides, that were previously effective in curbing infestations [2][5]. Together, these elements create a picture of the complexity when dealing with this ‘wicked problem’ effectively. Solving Vancouver’s rat infestation requires an approach that takes environmental, legal, and urban planning considerations into account while addressing public health and ethical concerns.

Impacts of Climate Change on Rat Breeding

Factors Affecting Rat Breeding

Rat populations fluctuate throughout the seasons as temperature, light, and food sources change.[6][7] The optimal rat breeding temperature ranges from 12-28 °C.[7] Additionally, lighting has been shown to affect rat breeding cycles, in which rats reproduce optimally following a diurnal cycle of 14 hours light and 10 hours dark.[7] Because Vancouver experiences seasonality, there will be an increase in intensity of breeding in the spring, fall, and early summer; And there is a substantial decrease during the hot and dry summer periods, as well as the winter.[6][8] The annual breeding period starts around March, when the temperature and amount of daylight starts to increase.[6] The non-breeding seasons are distinguished by the lack of photosynthesis and plant growth, which in turn leads to less replenishment of food sources for the rats, as well as the nonoptimal rat breeding temperatures and light levels.[8] Additionally, the limited food sources during the cold seasons and poorer physiological conditions interact with pathogens causing higher mortality rates in rodents.[8]

Rats are experts at hiding, using their small size and agility to slip into narrow crevices and nest in hard-to-reach places.

Other Impacts of Climate Change on Rat Populations

There is strong evidence that suggests the warming average temperature in the Northern hemisphere correlates with growing seasons starting earlier, and also ending later.[9] Warmer temperatures mean that there will be longer periods of higher rates in primary production which will in turn provide more food for rats.[9] Furthermore, there is also a strong correlation with climate warming causing an increase in insect populations, which is another food source for rats.[10] Due to more intense disturbances, specifically during the drought season, plant defense systems are weaker, due to increased environmental stressors making them more susceptible to insects.[10] To add, the longer periods of warmer weather increases the time in which insects are active.[11] Therefore, insects have more easily accessible food sources, as well as better physiological conditions due to the warmer temperatures, which is causing increase in insect populations.[6]

Implications on Greater Vancouver

There is not a lot of definitive evidence that the rat populations in greater Vancouver are rising specifically due to climate change; However, Kaylee Bryer of the Vancouver Rat Project mentions that it can still be inferred climate change, and the warming winters are a contributing factor.[12]

As Vancouver has had a 2.4 °C average temperature increase, according to the City of Vancouver Climate Change Adaptation Strategy 2024-2025, rat populations are expected to rise.[6][13] Firstly, due to climate warming, there are longer plant growing seasons, as well as longer active periods for insects causing insect populations to rise.[9][11] Therefore, there are longer periods of which there is higher food availability for rats. Secondly, climate change and the warmer weather means that there will simply be a longer period of optimal rat breeding conditions.[7] Thirdly, there will be less rat mortality in the winter because of the increased food availability for longer, and milder winters which carry better physiological conditions for rats.[8] With longer breeding periods, as well as lower mortality rates during the winter means that rat populations are predicted to increase at an exponential rate in greater Vancouver.[12]

Impacts of Rat Infestations in Vancouver

Vancouver’s growing incidences of rat infestations has sparked discussions regarding the public health risks they pose (both physical and psychological). As reported recently in a piece by the Canadian Broadcasting Corporation (CBC), Vancouver's pest control workers have raised concerns about the rising rat population in the city, asserting that “we’re getting rat calls in places we’ve never really gotten before”.[14] In addition to physical and social risks, rat infestations can cause economic hardship for Vancouverites by damaging property and infrastructure. Despite the widespread concerns about rat infestations, not much research has been devoted towards studying and addressing the problem, which has led to a lack of good data to support new and ongoing initiatives.

Physical Health Risks

Rats can carry and transmit diseases to humans and animals through their urine, droppings, saliva, bites, and indirectly via fleas, ticks, or mites.

Vancouver’s increasingly frequent rat infestations present a range of physical health risks, most notably the ability of rats to carry pathogens transmissible to the human population either directly or via intermediate hosts, including pets. A study conducted in 2015 examined over 400 rats in the Downtown Eastside of Vancouver (DTES) and found that one in four rats tested positive for Bartonella tribocorum, a pathogen that can be transmitted indirectly to humans and may cause symptoms such as endocarditis and neuroretinitis.[15] Moreover, a study performed following the outbreak of a pathogen among an unhoused community in the DTES, which was reportedly subject to contact with rats, detected the presence of multiple enteropathogens able to infect humans.[16] It should be noted that the physical health risks posed by rat infestations disproportionately affect the marginalized populations found in unhoused and low-income communities in Vancouver. Also, rat infestations often lead to the contamination of water and food sources, increasing the incidence and spreading of foodborne illnesses.[17] This issue is most critical among the disadvantaged groups inhabiting Vancouver’s downtown areas, due to rats’ increased population density and closer proximity to food sources. Finally, some documented cases of the transmission of human illnesses through rat bites have been reported for Vancouver and Vancouver Island.[18]

Psychological and Mental Health Risks

Apart from physical health risks, it has been shown that a high prevalence of rats in a community can induce fear and anxiety, leading to psychological stress and deteriorating mental health in susceptible individuals.[19] Again, these issues most intensely affect populations in low income neighborhoods. A survey performed in 2021 in Chicago–the American city with the highest number of rat complaints–found that even after accounting for differences in socio-demographics and neighborhood conditions, respondents who saw rats near-daily had a ~5.5 times higher likelihood of declaring high depressive symptoms relative to those who saw rats less frequently.[20] This is perhaps not surprising when it is considered that the fear of rats or mice (musophobia) is one of the most common phobias of animals experienced by humans and is generally experienced far out of proportion to the actual risks posed by rodents today.[21]

Economic Implications

In addition to the physical and mental health risks linked to rat infestations, they can cause a serious financial burden on businesses and individuals/families. For one, the need for businesses to swiftly deal with rat infestations in order to pass health inspections and adhere to food safety regulations can prove costly, tedious, and stressful. Likewise, many families and individuals must cover the high cost of pest control solutions if they wish to maintain a sanitary home environment. Secondly, foodborne illnesses, pathogens and other health-related risks due to rats can place a burden on government services such as hospitals and mental help programs. Also, rat infestations commonly lead to costly damage to infrastructure and property, which can arise, for example, from the animals biting through hard-to-access wiring (this has even led to electrical fires) or nesting in insulation/drywall.

Concerns Regarding Insufficient Data

Despite the impacts of rat infestations in Vancouver, only a limited number of large-sample-size studies have been conducted and there remain substantial gaps in the data needed to establish an informed conclusion and effective strategy to deal with this problem. Furthermore, the majority of studies to date have been conducted in the DTES, which has limited the amount of information relevant to the broader lower mainland. Nevertheless, the topic of rat infestations has been well studied from a global perspective, so it may be possible to use research data obtained from studies conducted abroad to draw conclusions relevant to the broader lower mainland region of British Columbia.

Potential Solutions and Effectiveness of Vancouver’s Rat infestation

Trapping rats is recommended to reduce rat infestations

City of Vancouver Solutions and Effectiveness

The City of Vancouver has identified and implemented several measures to face the rat infestations. These strategies include removing rodents’ habitat, excluding them from indoors, and removing their nutrient sources.[22] Not only this but Vancouver has been encouraging the local community to take action as well, emphasizing prevention through community education on reducing rodent attractants.[22] Encouraging building owners to seal entry points and regularly inspect for signs of infestation.[22] They are instructing strategies to control the infestation of rats and mice effectively, mainly by eliminating everything for the rodents’ survival.[22] For example, proper composting techniques to remove their food source, increase the number of traps, and seal holes and cracks in the foundation, walls, floors, and roof.[22][5] Vancouver engaging the community can reduce the human-driven factors that sustain rat populations and foster a collaborative approach to pest control.[22] While these methods are more sustainable, the effectiveness and success depend on public compliance and coordinated citywide efforts.[22] Some gaps exist in scalability and rapid response to ongoing infestations.[22]

Rodenticides Banned Effectiveness and Solution

One significant measure involved the decision to ban certain rodenticides, which was influenced by concerns of secondary wildlife poisoning.[5][23] These are strong rat poisons that impair the blood coagulation of rats and other rodents causing internal bleeding, causing them to die in days.[5] The rodenticides were killing non-target animals such as owls, hawks, and eagles, along with creatures that consumed rats and mice.[5][23] They were widely used due to their effectiveness in controlling large rodent populations.[5] Although this incentive of banning the rodenticides benefited other species, this decision has considerably intensified the city-wide rat infestation problems.[5] This ban has translated to higher challenges with the current approaches, while environmentally friendly, may not yet fully meet the practical demands of managing a growing population of rats.[5] Experts suggest a potential solution of reconsidering rodenticide restrictions to allow limited, targeted use under strict conditions.[5] This involves deploying rodenticide in closed areas inaccessible to non-target wildlife and restricting use to critical areas like industrial zones or high-infestation locations.[5]

Integrated Pest Management (IPM) Solutions

Baby rats are social and thrive in groups, learning behaviours and skills from their siblings and mother

The Integrated Pest Management (IPM) main focus includes the integration of biological, mechanical, and environmental controls with community engagement and education.[24] Rats in urban areas are constantly reproducing and can thus always overcome control measures, meaning that there should be constant improvement in the measures employed and scaling of the same to those areas which have the problem.[24] The measures taken by the city correspond only to some extent to the principles of IPM, and the use of other types of controls. The lack of effective rodenticides do not meet the adaptive characteristics of rat populations.[24] The research of the Integrated Pest Management (IPM) suggests that participation and engagement of the communities and additional investment in new tools are critical to the improvement of the results.[24]

Solution to Climate Change

Incorporating climate-resilient pest control strategies were also discussed as a potential solution.[5] Modifying seasonal pest control schedules to align with warmer winters and extended breeding seasons can eliminate extensive rat breeding.[5] Along with the enhanced stormwater and sewer systems to prevent rats from using them as nesting grounds ensures proactive management and limits rat population growth.[5] These proposed strategies are essential for adapting to changing environmental conditions, and ensuring the management and limitations to the rats population growth.[5] The City of Vancouver has not explicitly outlined measures to counteract the effects of warmer winters.[5]

Monitoring and Tracking Solution

However, the main issue arises from the City of Vancouver's current struggle with tracking and monitoring.[24] Vancouver offers numerous opportunities for rat populations to reside due to crowded housing areas, infrastructure, dense populations, and an infinite source of food.[24] Such elements make monitoring especially difficult because the rats can easily move or even disappear into the holes that are difficult to access.[24] Which severely hinders the city’s ability to learn and adapt to the ongoing pest infestation.[24] The city of Vancouver relies heavily on public complaints to identify rat hotspots, leading to inconsistent and incomplete data.[24] This could lead infestations to go unnoticed, especially in areas where residents are unaware of the reporting process or reluctant to engage.[24] Improved data and research on the infestations, along with tracking and monitoring systems, would be beneficial to discover a solution to rat infestations.[24] Regular monitoring and data collection can be used to track rat activity and adjust strategies accordingly.[24] With this data we are able to encourage eco-friendly pest control businesses to innovate and provide accessible services.[24] Creating pilot programs in neighborhoods with high infestation rates to test new traps, barriers, and community education models can collect data on what interventions yield the best results for scaling citywide.[22][5] This information can improve the communication and coordinated efforts between city departments, pest management professionals, and public health agencies.[24]

Conclusion

As a result of a combination of factors, including climate change intensification, easy access to primary food sources, and a B.C.-wide ban on anticoagulant rodenticides, the Vancouver rat infestation problem has substantially intensified. This surging rat population has far-reaching negative implications, such as physical health impacts (pathogens), mental health impacts (symptoms of depression), and financial burden (infrastructure/property damage). Given that many of these factors will likely worsen in future years, it is expected that this problem will be amplified. This highlights the importance for British Columbia and the City of Vancouver to enact effective initiatives and countermeasures to combat the issue. These may include addressing climate change, implementing Integrated Pest Management (IPM) solutions, or even unbanning certain anticoagulant rodenticides. Although as was mentioned, more data should be collected to execute on informed decisions.

References

Please use the Wikipedia reference style. Provide a citation for every sentence, statement, thought, or bit of data not your own, giving the author, year, AND page. For dictionary references for English-language terms, I strongly recommend you use the Oxford English Dictionary. You can reference foreign-language sources but please also provide translations into English in the reference list.

Note: Before writing your wiki article on the UBC Wiki, it may be helpful to review the tips in Wikipedia: Writing better articles.[25]

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Himsworth, C. G., Feng, A. Y., Parsons, K., Kerr, T., & Patrick, D. M. (2013). "Using experiential knowledge to understand urban rat ecology: a survey of Canadian pest control professionals". Urban Ecosystems. 16: 341–350.CS1 maint: multiple names: authors list (link)
  2. ↑ 2.0 2.1 2.2 2.3 2.4 McSheffrey, E. (February 6, 2024). "Is warm weather driving a rat rise in Vancouver? -BC". Global News.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Orkin Canada (October 28, 2024). "British Columbia's top 20 "rattiest" cities 2024".
  4. ↑ 4.0 4.1 4.2 Dillon Consulting (November 15, 2022). "City of Vancouver Street Litter Audits 2022 Results" (PDF).
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 5.18 5.19 Shen, Nono (February 9, 2024). "Vancouver grapples with rat infestation: Experts link rise in rodents to provincial ban on a type of pest poison and unusually warm winter". The Canadian Press. Retrieved November 2, 2024.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 "The changing seasons". DC Health. Retrieved November 30, 2024.
  7. ↑ 7.0 7.1 7.2 7.3 Bayons, T., Hanwell, D., Turner, P., Niel, L., Xiao, C., St. Arnaud, R., & Smith, E. (February, 2020). CCAC guidelines: Rats. 190 O’Connor St., Suite 800 Ottawa, Ontario, K2P 2R3: Canadian Council on Animal Care. p. 33. ISBN 978-0-919087-81-1. line feed character in |location= at position 28 (help); Check date values in: |year= (help)CS1 maint: multiple names: authors list (link) CS1 maint: location (link)
  8. ↑ 8.0 8.1 8.2 8.3 Andreassen, H. P., Sundell, J., Ecke, F., Halle, S., Haapakoski, M., Henttonen, H., Huitu, O., Jacob, J., Johnsen, K., Koskela, E., Luque-Larena, J. J., Lecomte, N., Leirs, H., Mariën, J., Neby, M., Rätti, O., Sievert, T., Singleton, G. R., van Cann, J., … Ylönen, H. "Population cycles and outbreaks of small rodents: ten essential questions we still need to solve". Oecologia. 195: 601–622 – via National Institutes of Health.CS1 maint: multiple names: authors list (link)
  9. ↑ 9.0 9.1 9.2 Gonsamo A, Chen JM, Ooi YW (December 1, 2017). "Peak season plant activity shift towards spring is reflected by increasing carbon uptake by extratropical ecosystems". Global Change Biology. 24: 2117–2128 – via Wiley Online Library.CS1 maint: multiple names: authors list (link)
  10. ↑ 10.0 10.1 "Forest Pests and Climate Change". Climate Atlas of Canada.
  11. ↑ 11.0 11.1 Eickermann, M., Junk, J., & Rapisarda, C. (July 31, 2023). "Climate Change and Insects". Insects. 14 – via National Library of Medicine.CS1 maint: multiple names: authors list (link)
  12. ↑ 12.0 12.1 Ruttle, Joseph (September 29, 2024). "Vancouver's rat problem: Why are there so many, and what now?". Vancouver Sun. Retrieved November 30, 2024.
  13. ↑ "Climate change adaptation strategy" (PDF). City of Vancouver. Retrieved November 30, 2024.
  14. ↑ "Social media video of rats in downtown Vancouver renews debate over pest control". Canadian Broadcasting Corporation. February 07, 2024. Retrieved December 07, 2024. Check date values in: |access-date=, |date= (help)
  15. ↑ Himsworth, Chelsea; Bai, Ying; Kosoy, Michael; Wood, Heidi; DiBernardo, Antonia; Lindsay, Robbin; Bidulka, Julie; Tand, Patrick; Jardine, Claire (January 28, 2015). "An investigation of Bartonella spp., Rickettsia typhi, and Seoul hantavirus in rats (Rattus spp.) from an inner-city neighborhood of Vancouver, Canada: is pathogen presence a reflection of global and local rat population structure?". Journal of Vector-Borne Zoonotic Diseases. Volume 15, no. 1 – via PubMed. Unknown parameter |author-name-separator= ignored (help); Unknown parameter |author-separator= ignored (help)
  16. ↑ Lee, Lisa; Himsworth, Chelsea; Byers, Kaylee; Atwal, Harveen; Gabaldon, Gus; Ritchie, Gordon; Lowe, Christopher; Matic, Nancy; Chorlton, Samuel (October 16, 2023). "Detection of multiple human enteropathogens in Norway rats (Rattus norvegicus) from an under-resourced neighborhood of Vancouver, British Columbia". PLos Neglected Topical Diseases. Volume 17, no. 10 – via PubMed.
  17. ↑ "Getting rid of rodents (rats and mice)". Health Link BC. January 31, 2024. Retrieved December 8th, 2024. Check date values in: |access-date= (help)
  18. ↑ Hanson, Kendall (March 6, 2024). "Port Alberni woman diagnosed with rat-bite fever faces surgery". Chek News. Retrieved December 8, 2024.
  19. ↑ Battersby, S.; Parsons, R.; Webster, J. (2002). "Urban rat infestations and the risk to public health". Journal of Environmental Health Research. Volume 1, no. 2: 4–12.
  20. ↑ Murray, Maureen; Byers, Kaylee; Buckley, Jacqueline; Magle, Seth; German, Danielle (April 2024). "Associations between Rat Infestations and Mental Health Vary by Gender, Race, and Income in Chicago". Journal of Urban Health. Voume 101, no. 2: 318–326 – via PubMed.
  21. ↑ Murphy, Nicole (August 8, 2022). "What is Musophobia?: Triggers, causes, symptoms & treatment". CPD Online College Knowledge Base. Retrieved December 8, 2024.
  22. ↑ 22.0 22.1 22.2 22.3 22.4 22.5 22.6 22.7 22.8 City of Vancouver (n.d.). "Rats and mice". Vancouver.ca. Retrieved November 2, 2024.
  23. ↑ 23.0 23.1 Little, Simon (April 10, 2023). "B.C.'s rodenticide ban could be having unintended consequences: Pest control industry". Global News. Retrieved November 2, 2024.
  24. ↑ 24.00 24.01 24.02 24.03 24.04 24.05 24.06 24.07 24.08 24.09 24.10 24.11 24.12 24.13 Parsons, M. H., Banks, P. B., Deutsch, M. A., Corrigan, R. F., & Munshi-South, J. (2017). "Trends in urban rat ecology: a framework to define the prevailing knowledge gaps and incentives for academia, pest management professionals (PMPs) and public health agencies to participate". Journal of Urban Ecology. 3(1), jux005.CS1 maint: multiple names: authors list (link)
  25. ↑ En.wikipedia.org. (2018). Writing better articles. [online] Available at: https://en.wikipedia.org/wiki/Wikipedia:Writing_better_articles [Accessed 18 Jan. 2018].


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