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Fertility control is often heralded as a humane and effective technique for management of overabundant wildlife, including rodents. The intention is to reduce the use of lethal and inhumane methods, increase farm productivity and food security as well as reduce disease transmission, particularly of zoonoses. We developed a framework to guide researchers and stakeholders planning to assess the effectiveness of a potential contraceptive agent for a particular species. Our guidelines describe the overarching research questions which must be sequentially addressed to ensure adequate data are collected so that a contraceptive can be registered for use in broad‐scale rodent management. The framework indicates that studies should be undertaken iteratively and, at times, in parallel, with initial research being conducted on (1) laboratory‐based captive assessments of contraceptive effects in individuals; (2) simulation of contraceptive delivery using bait markers and/or surgical sterilization of different proportions of a field‐based or enclosure population to determine how population dynamics are affected; (3) development of mathematical models which predict the outcomes of different fertility control scenarios; and (4) implementation of large‐scale, replicated trials to validate contraceptive efficacy under various management‐scale field situations. In some circumstances, fertility control may be most effective when integrated with other methods (e.g. some culling). Assessment of non‐target effects, direct and indirect, and the environmental fate of the contraceptive must also be determined. Developing fertility control for a species is a resource‐intensive commitment but will likely be less costly than the ongoing environmental and economic impacts by rodents and rodenticides in many contexts. [ABSTRACT FROM AUTHOR]

This article reports that rapid recolonization can be a major problem for the management of overabundant populations if the removal techniques are short term. Continuous removal of individuals minimize rapid recolonization, but it could profoundly alter the population's composition and may in fact separate individuals of high quality from individuals of low quality. If residents were removed and immigration occurred quickly, immigrants would be present in the population and create a bias towards individuals of low quality, assuming that immigrants are of low quality. Trap barrier systems (TBS) were introduced to some Southeast Asian countries for rodent management. If a TBS removed mainly dispersers of low quality and left the resident population intact, the quality of residents near a TBS would be similar to rats in areas without a TBS. Researchers selected 6 experimental plots in irrigated rice monoculture. Each plot was adjacent to a main irrigation channel of 6-m width. The fumigation of burrows was thought to yield residents. Rats were fumigated and dug out of their burrows in the centre of 1 quadrant of the semicircle per trapping session in treatment plots and control plots.

The article discusses various reports published within the issue, including one about life-history traits, food supply and population dynamics of the white-footed mouse, and another on rodent management.

Background: Understanding the ecological processes that are involved in the transmission of zoonotic pathogens by small mammals may aid adequate and effective management measures. Few attempts have been made to analyze the ecological aspects that influence pathogen infection in small mammals in livestock production systems. We describe the infection of small mammals with Leptospira spp., Brucella spp., Trichinella spp. and Cysticercus fasciolaris and assess the related intrinsic and extrinsic factors in livestock production systems in central Argentina at the small mammal community, population and individual levels. Methodology/Principal findings: Ten pig farms and eight dairy farms were studied by removal trapping of small mammals from 2008 to 2011. Each farm was sampled seasonally over the course of one year with cage and Sherman live traps. The 505 small mammals captured (14,359 trap-nights) included three introduced murine rodents, four native rodents and two opossums. Leptospira spp., anti-Brucella spp. antibodies and Trichinella spp. were found in the three murine rodents and both opossums. Rattus norvegicus was also infected with C. fasciolaris; Akodon azarae and Oligoryzomys flavescens with Leptospira spp.; anti-Brucella spp. antibodies were found in A. azarae. Two or more pathogens occurred simultaneously on 89% of the farms, and each pathogen was found on at least 50% of the farms. Pathogen infections increased with host abundance. Infection by Leptospira spp. also increased with precipitation and during warm seasons. The occurrence of anti-Brucella spp. antibodies was higher on dairy farms and during the winter and summer. The host abundances limit values, from which farms are expected to be free of the studied pathogens, are reported. Conclusions/Significance: Murine rodents maintain pathogens within farms, whereas other native species are likely dispersing pathogens among farms. Hence, we recommend preventing and controlling murines in farm dwellings and isolating farms from their surroundings to avoid contact with other wild mammals. [ABSTRACT FROM AUTHOR]

Rodents are among the most damaging pests in agriculture worldwide. High-density populations of rodent pests can kill plants or diminish their growth, and reduce both fruit size and the number of seeds. Therefore, rodent pests can lead to considerable crop loss and require management actions to minimize damage. Optimal management of pest rodents is usually based on the combination of methods to reduce damage. Although rodenticides are usually the most commonly deployed approach, they have undesirable side effects. Consequently, more environmentally benign approaches such as repellents or attractants to lure rodents away from fields are gaining traction. The dispersal of a large number of juvenile males at certain times of year has prompted us to focus on male rodents for our experiments. We used laboratory feeding experiments to measure how the odor of plant secondary metabolites (PSMs) affects two pest rodents: common voles ( Microtus arvalis, Pallas) and house mice ( Mus musculus, L.). We tested eighteen different PSMs or combinations thereof with voles. Four PSMs reduced feeding and seven PSMs increased feeding of male common voles. Five of six tested odors were effective as repellents against house mice. However, we assume a species-specific response to volatile PSMs repellents. This study demonstrated that four repellents reduced feeding in both rodent species. Our results contribute to the development of non-lethal management tools for rodent pest species that are potentially more suitable than traps and rodenticides. This approach could be applicable to a variety of crops if effective at field conditions. [ABSTRACT FROM AUTHOR]

Simple Summary: Trapping particular small mammal species is frequently used for scientific purposes but unnecessary bycatch can occur. Live trapping conducted over the last decade in Germany using Ugglan multiple capture traps in grassland, forest and margin habitats revealed about 30% bycatch when target species were common voles (Microtus arvalis) in grassland and common voles and bank voles (Clethrionomys glareolus) in margins and forests. This was more pronounced in spring and along margins. Species mentioned on the early warning list according to the Red List Germany were higher in numbers and proportion in spring and in grassland. The results of the study will help to avoid periods with enhanced presence of bycatch including endangered species (if the purpose of the study allows) or to pay particular attention in certain seasons and habitats when the occurrence of bycatch is most likely. Trapping small mammals is frequently used to study the dynamics, demography, behavior and presence of pathogens. When only particular small mammal species are in the focus of interest, all other species are unnecessary bycatch. We analyzed data from extensive live trapping campaigns conducted over the last decade in Germany, following a consistent standard trapping protocol that resulted in about 18,500 captures of small mammals. Animals were trapped with Ugglan multiple capture traps in grassland, forest and margin habitat. Trap success and the proportion of bycatch were about 30% when target species were common voles (Microtus arvalis) in grassland and common voles and bank voles (Clethrionomys glareolus) in margins and forests. This was more pronounced in spring and along margins. Species mentioned in the early warning list according to the Red List Germany were higher in numbers and proportion in spring and in grassland. The results will help to avoid periods with enhanced presence of bycatch, including endangered species (if the purpose of the study allows) or to pay particular attention in certain seasons and habitats when the occurrence of bycatch is most likely. [ABSTRACT FROM AUTHOR]

DNA‐based approaches have greatly improved the applicability of dietary studies aimed at investigating ecological processes. These studies have provided direct insights into, otherwise difficult to measure, interactions between species and trophic levels, food web structure and ecosystem functioning. However, despite these advances, DNA‐based methods have struggled to accurately quantify the whole breadth of diet constituents because of methodological biases, such as amplification bias and digestive processes. The present study is, to our knowledge, the first diet study to use droplet digital PCR to quantify diet constituents. We manipulated the diet of wild‐caught wood mice (Apodemus sylvaticus) by feeding them with a known amount of small vegetable seeds (onion and carrot) and quantified the DNA traces of these diet constituents in faecal samples. The sensitivity of the technique combined with the control on the experimental design allowed mitigation of methodological bias. We were able to accurately determine DNA concentrations of small vegetable seeds in the diet of wood mice. Quantification of target DNA demonstrated significant differences in DNA content when one vs. five seeds were consumed. These differences remained significant when the age, sex and other diet constituents of the mice were altered. Different DNA markers, targeting different parts of the chloroplast, influenced onion DNA detectability. However, all onion and carrot markers showed higher DNA content for higher seed numbers. Overall, the sensitive DNA‐based approach developed in this study allows for minimally invasive quantification of small diet constituents in faeces, which would otherwise be undetectable with traditional methods. [ABSTRACT FROM AUTHOR]

In this study, the ecological effects of culling programs are considered in the context of rodent pest management. Despite the escalation of rodent problems globally, over the past quarter of a century there have not been many new developments in culling programs directed at managing these populations. There is a strong reliance on broad scale use of chemical rodenticides or other lethal methods of control. The ecological consequences of culling programs based on chemical rodenticides and bounty systems are considered. Although rodents cause tremendous economic hardship to people on a continental scale, usually less than 10% of species cause substantial impacts. Indeed, many species of rodent provide important “ecological services” and, given that culling programs rarely distinguish between rodent species, often the non-pest rodents are at grave risk. Rodent control is conducted with little appreciation of what proportion of the population would need to be culled for a significant reduction in economic damage. In Indonesian rice fields, once rodent densities are high then a reduction in yield loss from 30% to 15% would require more than 75% of the population to be culled; a reduction to less than 5% yield loss would require more than a 95% cull. The negative ecological consequences of culling can be better managed if the method is specifically tailored to the species that need to be managed. A greater emphasis on ecologically-based rodent management would assist markedly in reducing the unwanted and unintended effects of culling. [ABSTRACT FROM AUTHOR]

Survey techniques available to sample mammals have multiplied during the last decades. They offer new opportunities for sampling and monitoring populations, but before widespread use they need to be validated and calibrated to more traditional approaches. We conducted a quantitative assessment of hair tubes designed to monitor common small mammals by comparing results to live-trapping data. Hair tubes are inexpensive, easy to use, and noninvasive, which offers benefits regarding animal ethics. We considered the shape of the tube, application in field conditions, and validated hair-tube results in 3 different habitats based on experimental and field sampling in 2 countries. Tube size selected species entering into the tubes, with shrews detected in small tubes only and rodents in larger tubes. The number of tubes visited (with hair sample) was proportional to the number of individuals captured in live traps. Overall, tubes performed better than traps, detecting individuals where traps did not, making this technique promising for inventory of rare species. The sampling pattern was robust across wood, grassland, and cultivated field habitats and across seasons, which suggests that the proportion of hair tubes visited is a robust indicator of relative abundance of small mammals. In the context of population studies, hair tubes cannot replace trapping because the identification of species or individuals from hair collected in tubes is difficult and costly. We recommend combining hair tubes with livetrapping for increased efficiency and before species identification based on DNA sampling is applied to large-scale population studies. [ABSTRACT FROM AUTHOR]

Rodents, including common voles ( Microtus arvalis) and house mice ( Mus musculus) cause immense pre-harvest and post-harvest losses. Therefore, developing methods that mitigate these losses while maintaining their role in ecosystems is a priority. Several plant secondary metabolites (PSM) which significantly reduce food intake of both species under laboratory conditions have been identified. However, before these can be used in rodent pest management, they must be tested under more natural conditions where other food sources are available. In this study, the odors of 4 PSMs were evaluated for their repellent effects in experiments conducted in semi-natural enclosures. Soil treated with PSMs or untreated soil (experimental control) was placed in an underground box containing food (rolled oats). We quantified the number of visits to each box and could demonstrate that all 4 PSMs reduced the number of visits to treatment boxes in both rodent species. For common voles the combination of methyl nonyl ketone + black pepper oil was the most repellent PSM. House mice made fewer visits to all PSM boxes; boxes with the anthraquinone were visited least. Furthermore, house mice consumed less food from boxes containing soil treated with all 4 PSMs. Our results suggest that PSMs are repellent in murid and microtine rodents under semi-field conditions. In addition, the future use of PSM odors for repelling both pest species, especially house mice, seems promising. Further investigations with other PSMs, different concentrations as well as alternative application methods are needed to repel common voles from attractive crops. [ABSTRACT FROM AUTHOR]

The vast number of plant secondary metabolites (PSMs) produced by higher plants has generated many efforts to exploit their potential for pest control. We performed a systematic literature search to retrieve relevant publications, and we evaluated these according to PSM groups to derive information about the potential for developing plant-derived rodent repellents. We screened a total of 54 publications where different compounds or plants were tested regarding rodent behavior/metabolism. In the search for widely applicable products, we recommend multi-species systematic screening of PSMs, especially from the essential oil and terpenoid group, as laboratory experiments have uniformly shown the strongest effects across species. Other groups of compounds might be more suitable for the management of species-specific or sex-specific issues, as the effects of some compounds on particular rodent target species or sex might not be present in non-target species or in both sexes. Although plant metabolites have potential as a tool for ecologically-based rodent management, this review demonstrates inconsistent success across laboratory, enclosure, and field studies, which ultimately has lead to a small number of currently registered PSM-based rodent repellents. [ABSTRACT FROM AUTHOR]

Worldwide pest rodents on livestock farms are often regulated using anticoagulant rodenticides (ARs). Second generation ARs in particular can cause poisoning in non-target species due to their high toxicity and persistence. However, research on exposure of small mammals is rare. We systematically investigated spatial and temporal exposure patterns of non-target small mammals in a large-scale replicated study. Small mammals were trapped at different distances to bait stations on ten farms before, during and after brodifacoum (BR) bait application, and liver samples of 1178 non-target small mammals were analyzed for residues of eight ARs using liquid chromatography coupled with tandem mass spectrometry. BR residues were present in 23% out of 742 samples collected during and after baiting. We found clear spatial and temporal exposure patterns. High BR residue concentrations mainly occurred within 15 m from bait stations. Occurrence and concentrations of residues significantly decreased with increasing distance. This pattern was found in almost all investigated taxa. After baiting, significantly more individuals contained residues than during baiting but concentrations were considerably lower. Residue occurrence and concentrations differed significantly among taxa, with the highest maximal residue concentrations in Apodemus species, which are protected in Germany. Although Sorex species are known to be insectivorous we regularly found residues in this genus. Residues of active agents other than brodifacoum were rare in all samples. The confirmation of substantial primary exposure in non-target small mammals close to the baiting area indicates considerable risk of secondary poisoning of predators, a pathway that was possibly underestimated until now. Our results will help to develop risk mitigation strategies to reduce risk for non-target small mammals, as well as their predators, in relation to biocidal AR usage. [ABSTRACT FROM AUTHOR]

Tula orthohantavirus (TULV) is a rodent-borne hantavirus with broad geographical distribution in Europe. Its major reservoir is the common vole (Microtus arvalis), but TULV has also been detected in closely related vole species. Given the large distributional range and high amplitude population dynamics of common voles, this host–pathogen complex presents an ideal system to study the complex mechanisms of pathogen transmission in a wild rodent reservoir. We investigated the dynamics of TULV prevalence and the subsequent potential effects on the molecular evolution of TULV in common voles of the Central evolutionary lineage. Rodents were trapped for three years in four regions of Germany and samples were analyzed for the presence of TULV-reactive antibodies and TULV RNA with subsequent sequence determination. The results show that individual (sex) and population-level factors (abundance) of hosts were significant predictors of local TULV dynamics. At the large geographic scale, different phylogenetic TULV clades and an overall isolation-by-distance pattern in virus sequences were detected, while at the small scale (<4 km) this depended on the study area. In combination with an overall delayed density dependence, our results highlight that frequent, localized bottleneck events for the common vole and TULV do occur and can be offset by local recolonization dynamics. [ABSTRACT FROM AUTHOR]