Prevention or poisoning? Dilemmas in urban rats control (original) (raw)
Population responce of rodents to control with rodenticides
We summarize theoretical approaches and practice of rodent pest control in Russia and former USSR during last 50 years. We review literature as well as original data to understand mechanisms of rodent populations recovery after chemical control campaigns in urban areas, agricultural lands and natural foci of plague. Laboratory and field experiments indicate that inherent individual variation in behavioural, physiological and life-history traits provides survival of heterogeneous mix of individuals in residual population with increased resistance to poisonous baits and high reproductive potential that leads to fast recovery of a population. In a series of field experiments with various rodent and lagomorph species (Mus musculus, Rattus norvegicus, Meriones unguiculatus, M.meridianus, M.tamariscinus, Ochotona pallasii) we have shown that patterns of recolonization of depopulated area and mechanisms of population recovery vary among species and depend on species-specific social organization. After control territorial and group-living species demonstrated an increase in mobility and affiliative and marking behaviour and a decrease in intraspecific aggression. The rate of recolonization of treated areas was high due to redistribution of survived individuals and immigration by neighbors. Population recovered to original level due to increased breeding performance and fecundity of both survived residents and immigrants. In contrast, socially-independent species exhibited minor changes in behaviour. Recolonization was mainly due to better survival and recruitment of youngs, so the rate of recolonization was low. Species-specificity of behavioural compensation mechanisms to control should be considered when developing ecologically based rodent management strategies.
Liquid Fertility Management Bait Uptake by Urban Rats within New York City Subway Refuse Rooms
Proceedings of the Vertebrate Pest Conference, 2014
Traditional rodent management tools, such as traps and lethal rodenticides, are acute measures to reduce commensal rodent populations. Given the growing concerns regarding effectiveness, environmental safety, and animal welfare related to these tools, it has become imperative to find new methods. Fertility control is an emerging potential alternative to these tools as a safe, humane and effective method of long-term population management. SenesTech, Inc. has developed a liquid fertility management bait that causes follicle depletion in the ovaries of female Sprague Dawley rats and compromises sperm production in male Sprague Dawley rats in laboratory settings. These studies have shown significant decreases in litter sizes following bait consumption, but acceptance of this bait by wild rodents needed to be confirmed. Bait acceptance was tested within refuse rooms of the New York City subway system. Bait was provided ad libitum for 90 days. Uptake was evaluated by examining, via fluorescence microscopy, the presence of the bait marker rhodamine B, which manifests as fluorescent bands in whiskers. Presence of these bands indicated that 51% of the captured population had consumed the bait, and of these, 58% had taken the bait more than once. These results demonstrate that wild rats will consume a liquid fertility management bait, even in the presence of highly palatable and abundant food within the refuse rooms. This study establishes the successful acceptance of a bait by wild rats. Further investigation is needed to evaluate the effectiveness of this product for the management of urban Norway rat populations.
PLoS ONE, 2014
Norway and black rats (Rattus norvegicus and Rattus rattus) are among the most ubiquitous urban wildlife species and are the source of a number of zoonotic diseases responsible for significant human morbidity and mortality in cities around the world. Rodent ecology is a primary determinant of the dynamics of zoonotic pathogens in rodent populations and the risk of pathogen transmission to people, yet many studies of rat-associated zoonoses do not account for the ecological characteristics of urban rat populations. This hinders the development of an in-depth understanding of the ecology of ratassociated zoonoses, limits comparability among studies, and can lead to erroneous conclusions. We conducted a year-long trapping-removal study to describe the ecological characteristics of urban rat populations in an inner-city neighborhood of Vancouver, Canada. The study focused on factors that might influence the ecology of zoonotic pathogens in these populations and/or our understanding of that ecology. We found that rat population density varied remarkably over short geographical distances, which could explain observed spatial distributions of rat-associated zoonoses and have implications for sampling and data analysis during research and surveillance. Season appeared to influence rat population composition even within the urban environment, which could cause temporal variation in pathogen prevalence. Body mass and bite wounds, which are often used in epidemiologic analyses as simple proxies for age and aggression, were shown to be more complex than previously thought. Finally, we found that factors associated with trapping can determine the size and composition of sampled rat population, and thus influence inferences made about the source population. These findings may help guide future studies of rats and rat-associated zoonoses. Citation: Himsworth CG, Jardine CM, Parsons KL, Feng AYT, Patrick DM (2014) The Characteristics of Wild Rat (Rattus spp.) Populations from an Inner-City Neighborhood with a Focus on Factors Critical to the Understanding of Rat-Associated Zoonoses. PLoS ONE 9(3): e91654.
The Rationale for Culling of Rodent Litters. Agnish, N. D., and
1996
Based on a review of the pertinent literature and our own unpub-lished data, it is recommended that culling of rodent litters in the early postnatal period should be a standard practice in delivery-type reproduction studies. This, in turn, will reduce the litter size-induced variability in the growth and development of pups during the postnatal period and thus increase the sensitivity of statistical analyses to detect treatment-related effects. This will also ensure that any adverse effects on pup growth (body weight gain) and development (reflex and behavior development) are not masked by a treatment-induced reduction in Utter size. The culling should be carried out randomly and no attempt should be made to selec-tively cull sick or underweight pups. Since male pups weigh sig-nificantly more than females and studies have shown differences in maternal behavior toward one sex over the other, whenever possible each culled litter should consist of an equal number of males and females, ...
Population genetics and genotyping as tools for planning rat management programmes
Journal of Pest Science, 2018
Brown rats are a prolific synanthropic pest species, but attempts to control their populations have had limited success. Rat population dynamics, dispersal patterns, and resistance to rodenticides are important parameters to consider when planning a control programme. We used population genetics and genotyping to investigate how these parameters vary in contrasting landscapes, namely one urban and two rural municipalities from eastern France. A total of 355 wild brown rats from 5 to 6 sites per municipality were genotyped for 13 microsatellite loci and tested for mutations in the Vkorc1 gene which confers resistance to some rodenticides. Results revealed a strong genetic structure of the sampled rat populations at both regional (between municipalities) and local (between sites within municipalities) levels. A pattern of isolation by distance was detected in the urban habitat and in one of the rural municipalities. GeneClass and DAPC analyses identified 25 (7%) and 36 (10%) migrants, respectively. Migrations occurred mostly between sites within each municipality. We deduced that rat dispersal is driven by both natural small-scale movements of individuals and longer-distance (human-assisted) movements. Mutation Y139F on gene Vkorc1 was significantly more prevalent in rural (frequency 0.26-0.96) than in urban sites (0.00-0.11), likely due to differences in selection pressures. Indeed, pest control is irregular and uncoordinated in rural areas, whereas it is better structured and strategically organised in cities. We conclude that simultaneous pest control actions between nearby farms in rural habitats are highly recommended in order to increase rat control success while limiting the spread of resistance to rodenticides.
BJHS Themes, 2017
During the period from 1919 to 1970, rat killing was ‘modernized’: official, scientific, commercial, agricultural and county advisers sought ‘rat control’. Scientific expertise on rat parasites and rat control circulated internationally. The risks posed to human health through plague, as traced by researchers who were already expert on the third pandemic, led in the UK to the Rats and Mice (Destruction) Act 1919; and the United Nations Conference on Food and Agriculture, at Hot Springs, Virginia, USA, 1943 informed its replacement, the Prevention of Damage by Pests Act 1949. Anticoagulants such as Warfarin developed in the USA at first sold widely in the UK, then later British research on resistance informed subsequent American research. This UK application of international policy and science paralleled the emergence of an official case at Parliamentary level for the national, multidisciplinary and multi-agency approach to rats. Within the UK, animal ecologists under Charles Elton m...
Frontiers in Ecology and Evolution, 2022
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 path...
2005
In the present paper the feeding experiment with laboratory rats, conducted at the Ludwig Boltzmann Institute for Biological Agriculture from 1987-1989 is described in more detail to show the advantages, but also the difficulties of the method (Velimirov et al. 1992). Two groups of rats (Long Evans strain), each consisting of 20 pairs, were fed with products from organic resp. conventional growing systems. After chemical analyses of all products, vitamins, minerals and trace elements were added if needed to provide nutritionally balanced diets. With 2 harvests 3 generations (6 litters) were investigated. In the first litters significantly fewer offspring were born dead or died within the first week of their lives. The survival rate until weaning time at the age of 28 days and the weight development were slightly more successful. The weight gain of the female rats in connection with litter size and pup weight during lactation was significantly higher. But the change from the feed mix...
2020
A non-toxic liquid fertility control bait for rats has recently become commercially available (ContraPest from SenesTech, Inc.). This product contains two chemicals, both of which impair spermatogenesis in male and reduce ovulations in female rats. We tested the efficacy of this bait in wild-caught adult black rats from the island of Hawai’i in a short-term laboratory trial. A control group (n = 25) was offered placebo bait and the treatment group (n = 25) was offered fertility control bait, both ad libitum, during a 15-day introduction period and during the first of four breeding rounds, for a total of 58 days of exposure. After treatment, all rats were provided placebo bait for the remainder of the study and randomly paired with mates from within their treatment groups for two additional breeding cycles. Treatment and control groups comprised 10 breeding pairs each, with random re-pairings between breeding rounds. The treatment group produced no litters during the first and second...
The humaneness of rodent pest control
2003
Rat and mouse control methods potentially affect the welfare of many millions of animals every year. Here, the humaneness of the methods used in the UK and the USA is assessed in terms of their speed and mode of action, the appearance and behaviour of affected animals, experiences of human victims, long-term effects on animals that survive exposure, and welfare risks to non-target animals. Several methods emerge as relatively humane: cyanide, alpha-chloralose, electrocution traps and well-designed snap traps all usually kill swiftly and with little distress. Preventative methods such as rodent-proofing are also humane, as well as an essential-and probably under-used-component of effective control. However, anticoagulant poisons, the most common means of controlling rodents, generally take several days to kill, during which time they cause distress, disability and/or pain. Sub-lethally affected animals are also likely to experience haemorrhages and their sequelae, and carnivores feeding on affected rodents may be secondarily poisoned. The acute rodenticides zinc phosphide and calciferol are also generally inhumane, the former typically causing severe pain for several hours, and the latter, pain and illness for several days. Sticky boards, to which rodents become adhered by the feet and fur until they are killed or simply eventually die, also raise very serious welfare concerns. This evidence highlights remarkable paradoxes in the way society treats different classes of animal, and argues for more education, legislation and research targeted at reducing the vast numbers of rodents currently killed inhumanely.
In the present paper the feeding experiment with laboratory rats, conducted at the Ludwig Boltzmann Institute for Biological Agriculture from 1987-1989 is described in more detail to show the advantages, but also the difficulties of the method (Velimirov et al. 1992). Two groups of rats (Long Evans strain), each consisting of 20 pairs, were fed with products from organic resp. conventional growing systems. After chemical analyses of all products, vitamins, minerals and trace elements were added if needed to provide nutritionally balanced diets. With 2 harvests 3 generations (6 litters) were investigated. In the first litters significantly fewer offspring were born dead or died within the first week of their lives. The survival rate until weaning time at the age of 28 days and the weight development were slightly more successful. The weight gain of the female rats in connection with litter size and pup weight during lactation was significantly higher. But the change from the feed mix...
ContraPest®, a New Tool for Rodent Control
Proceedings of the Vertebrate Pest Conference, 2018
Lethal rodenticides and other lethal tools of managing commensal rodent populations long-term are not sustainable due to population rebounds and increasing resistance to rodenticides. The use of integrated pest management (IPM) programs are more prevalent due to consumer desire to decrease rodenticide use and utilize environmentally friendly, humane methods. IPM plans often require multiple tools to control an infestation, such as physical, biological and chemical measures. Here, we propose that rodent population management would benefit from a new tool aimed at targeting the biological source of overabundance: reproduction. SenesTech, Inc. (Flagstaff, AZ USA) has developed ContraPest ® , a liquid bait that limits the reproductive capacity of both male and female wild Norway and Roof rats. The two active ingredients, 4-vinylcyclohexene diepoxide (VCD) and triptolide, deplete all stages of follicles in the female and disrupt spermatogenesis in the male. Laboratory and field studies reveal that ContraPest ® is palatable and repeatedly consumed by rats even when provided with ad libitum food and water. Studies involving laboratory and wild caught rats have demonstrated a 93-100% reduction in litter sizes of rats treated with ContraPest ® compared to control rats. ContraPest ® was tested on free ranging rat populations in agricultural and urban settings. Rat populations on protein production farms decreased by an average of 46% following 100 days of treatment with ContraPest ®. In a complex urban environment, where property boundaries limit access to populations and foraging areas, ContraPest ® reduced the seasonal population peak by 67% after 133 days of baiting. These studies, combined with all of our field studies and population reduction models, demonstrate that ContraPest ® is a highly effective rodent contraceptive bait in a variety of environments. We strongly believe that adding/implementing fertility management via ContraPest ® to an IPM program would enhance long-term rodent population control in rural, urban, and agricultural environments.
Animal Welfare, 2023
Population control of the house mouse (Mus musculus), Norway rat (Rattus norvegicus) and black rat (Rattus rattus) is common practice worldwide. Our objective was to assess the impact on animal welfare of lethal and non-lethal control methods, including three dispatch methods. We used the Sharp and Saunders welfare assessment model with eight experts scoring eleven control methods and three dispatch methods used on the three species. We presumed the methods were performed as prescribed, only taking into account the effect on the target animal (and not, for example, on non-target catches). We did not assess population control efficacy of the methods. Methods considered to induce the least suffering to the target animal were captivebolt traps, electrocution traps and cervical dislocation, while those with the greatest impact were anticoagulants, cholecalciferol and deprivation. Experts indicated considerable uncertainty regarding their evaluation of certain methods, which emphasises the need for further scientific research. In particular, the impact of hydrogen cyanide, chloralose and aluminium phosphide on animal welfare ought to be investigated. The experts also stressed the need to improve Standard Operating Procedures and to incorporate animal welfare assessments in Integrated Pest Management (IPM). The results of our study can help laypeople, professionals, regulatory agencies and legislators making well-informed decisions as to which methods to use when controlling commensal rodents.
The current strategy of the pest management department of the Public Health Service in Amsterdam is to identify causal factors in order to reduce the carrying capacity of pest populations and to minimise the use of pesticides. Rats have been controlled with rodenticides for decades, which has increased the survival of resistant rats. Rodenticide resistance has now been found in several rat populations in Europe. The main aim of this study was to establish the relationship between brown rat (Rattus norvegicus) occurrence in Amsterdam and a number of environmental and socio-economic factors. A second aim was to point out factors that can be managed by the local authorities as a next step towards prevention and pro-active, integrated pest management. The paper begins with a short overview of the biology of the brown rat, with an accent on diseases and habitat factors. The number of rat reports at the neighbourhood level during the years 2009-2012 is then related to 16 environmental and socioeconomic variables including availability of water, availability of urban green space, sewer type, construction year of houses, property tax value, number of inhabitants and population composition. A generalised linear model was used; it had a negative binomial distribution and all candidate models were fitted with a maximum of five terms. The most significant terms were number of inhabitants, percentage of area occupied by urban green space, the percentage of houses with a construction year before 1960, and either the length of foul water sewer (separated sewer) or the length of combined sewer. Rats have a short generation time and can produce a large number of offspring. A rat population is therefore able to recover quickly from a reduction in number. It is therefore important to change the carrying capacity of the habitat in which rats are unwanted. This can be achieved by changing the amount of food and cover they can find. The results of the regression analysis suggest that houses constructed before 1960 and their gardens could be evaluated to see if there may be general solutions that would make them less amenable to rats. Furthermore, the results suggest that the structure of urban green space may be adapted to make it less attractive to rats; an example of this would be to replace evergreen shrubs with deciduous shrubs and to mow high vegetation near buildings more frequently. Moreover, the influence of waste near and in urban green space should be investigated. Finally, we suggest that the inspection and maintenance of sewers be continued and that this should include the connection between properties and the public sewer.
The Impact of Sterilized Females on Enclosed Populations of Ricefield Rats
Journal of Wildlife Management, 2004
For the sustainable management of small mammals, fertility control may be used in the future. Little is known about what proportions of females need to be sterilized to achieve an impact on population size and what compensatory processes may act on the population level. We tested the impact of surgical sterilization of zero, 25, 50, and 75% of females on the population dynamics and demography of enclosed populations of ricefield rats (Rattus argentiventer) and damage to rice crop. Sterilizing 50% of female founders (6 of 12) decreased population size at the end of the breeding season by about 50%. We used a simulation model, based on the breeding biology of the ricefield rat in the field and in the control enclosures, to generate the expected dynamics of the enclosure populations. The results suggested that compensation occurred in the enclosures where 75% of female founders (9 of 12) had been sterilized. We detected a slight tendency for 50% higher numbers of recent uterine scars in fertile founder females in the 50% and 75% treatments versus 25% treatments and controls (P = 0.198). The primary demographic mechanism for compensation was higher survival of young rats in enclosures where 75% of females were sterilized. However, compensation only partially offset the decrease in population size. We found no conclusive evidence that the reproductive output of F 1 generation females was higher when large proportions of female founders were sterilized. Early in the breeding season, the per capita damage to rice plants in populations without sterilized ricefield rats was increased. Our results suggest that the sterilization of >50% of females in ricefield rat populations can reduce rat population growth and rat damage to rice crops.
Integrative Zoology, 2021
The black rat is considered one of the world's top pests. With increased restrictions on rodenticides, new alternatives to manage rats are urgently needed. Research on the use of contraceptive hormones, levonorgestrel (LE), and quinestrol (QU), have been evaluated against some rodent species, and this research is the first study to assess these on black rats. Hormones were incorporated into rodent bait at 10 and 50 ppm concentrations singly and in combination (EP-1). Groups of 10 animals of each sex were fed the baits over 7 days. Lower bait consumption was observed with slight body mass reductions. On dissection, it was observed that the uterus was in a state of edema and male reproductive organs weighed less with reduced sperm counts/motility. The 2 most promising baits, 50 ppm QU and EP-1, were used to assess impact on pregnancy and litter size. Pregnancy was reduced from 70% success when both males and females consumed untreated bait, down to 30% when males had consumed contraceptive bait but females had not, and down to 0% when females had consumed contraceptive bait, regardless of whether they had paired with a treated or untreated male. Litter size in the untreated pairs was 8 pups, but only 4 pups in those cases where the male only had consumed the contraceptive. Further studies should investigate how long the effect lasts and its reversibility. Field studies at the population level may also shed light on the practicality of using contraceptive baits for black rats in different habitats.
Early detection and eradication of invading rats
2007
Invasive rats continue to colonize rat-free islands around the world. To prevent rats from establishing on rat-free islands, especially following their eradication, biosecurity actions are required to enable early detection and elimination. Rats arrive at islands by both human transportation and by swimming. There are very little data on the rates of rat transportation by humans, although it is known that they are not negligible. There are better data on the distances rats can swim, allowing estimates to be made of the risk of reinvasion of islands close to source populations. Biosecurity prioritization must take place across all rat-free islands, balancing the likelihood and impact of rat establishment. Dense grids of poison bait stations are not preferable for preventing rat invasion. Instead, surveillance systems that integrate multiple device types appear to be best for intercepting invading rats, but must be tested to ensure they are effective. This can be done by releasing a controlled number of monitored rats onto a rat-free island. Islands can now be maintained rat-free despite non-negligible reinvasion rates; however, in some cases islands must be managed within a larger meta-population context and eradication may never be achieved.