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Toekomst van het muskusrattenbeheer in Nederland. De mogelijkheden onderzocht
Abstract and Figures
In this study the possibilities are studied for complete removal of muskrat from the Netherlands. The study is in Dutch, but has an appendix in English. Three alternative strategies have been compared: a) The current strategy of year-round control at low densities b) No control, and c) Complete removal. The study provides information showing that complete removal is effective as a strategy and practically feasible as well. The direct costs are not prohibitive, and there are no significant negative effects (including indirect financial costs). In terms of water safety and costs, 'complete removal' is the best option compared to the other strategies. With this alternative, there are no risks for safety by burrowing muskrat anymore, no costs for repair of damage or economic damage to third parties. The control effort for the strategy 'complete removal' is clearly lower in the long term than under the year round scenario. Important benefits can also be identified in terms of animal welfare and effects on biodiversity. The risks that can occur with complete removal are manageable, and often smaller than under the current objective. The appendix presents a bio-economic model that was constructed to investigate under what assumptions eradication would be economically more optimal than year round control at any given equilibrium population density or no-control. This model and its result are presented in the appendix, in English.
Referaat
In de onderhavige studie worden de mogelijkheden bestudeerd om de muskusrat tot aan de landsgrens van Nederland terug te dringen. Het gaat om een strategie waarbij het aantal muskusratten in het binnenland van Nederland tot nul wordt teruggebracht en herkolonisatie wordt voorkomen.
Om hierover een goed publiek debat te kunnen voeren zijn drie alternatieve strategieën om de veiligheid te waarborgen tegen graverij door muskusratten met elkaar vergeleken.
Criteria waren onder andere het aantal te doden muskusratten, schades aan oever en waterkeringen, kosten en baten. De drie bestudeerde strategieën zijn: a) Vlakdekkend en jaarrond bestrijden, dat wil zeggen de huidige situatie b) Niet-bestrijden, en c) Terugdringen tot aan de landsgrens.
In de studie wordt informatie aangedragen waaruit blijkt dat terugdringen tot aan de landsgrens in principe kan, als praktische bezwaren of andere argumenten geen rol zouden spelen. De strategie is ook praktisch uitvoerbaar. De directe kosten zijn niet belemmerend, en er zijn geen noemenswaardige negatieve effecten (waaronder indirecte financiële kosten).
In termen van waterveiligheid en kosten is ‘Terugdringen tot aan de landsgrens’ de beste optie in vergelijking met de andere strategieën. Bij dit alternatief zijn er geen risico’s van graverij door muskusratten voor de veiligheid meer en geen kosten voor herstel van graverij, en schade bij derden. De benodigde bestrijdingsinspanning voor de strategie ‘Terugdringen tot aan de landsgrens’ is op lange termijn duidelijk lager dan onder jaarrond vlakdekkend bestrijden met de huidige doelstelling. Ook in termen van dierenwelzijn en effecten op de biodiversiteit zijn er belangrijke voordelen aan te wijzen.
De risico's die op kunnen treden bij ‘terugdringen tot aan de landsgrens’ zijn beheersbaar, en veelal kleiner dan onder de huidige doelstelling.
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... Trapping: The Netherlands is actively trapping coypu, muskrat, and American mink, and these traps could pose a threat to novel European mink. However, in their report, the Dutch Unie van Waterschappen (translates to Union of Water Boards) showed that through intensive trapping muskrat and coypu can be fully eradicated from the Netherlands (Bos & Gronouwe, 2018). They estimated this project to take an approximate 12 years, and would push muskrat back to the borders of the Netherlands with Germany. ...
In the past three decennia, a dozen mammal species were saved from the brink of extinction through conservation efforts such as reintroductions. The European mink (Mustela lutreola), as the most critically endangered mammal of Europe, requires increased conservation efforts to survive. Since the abolishment of American mink (Neovison vison) farms in the Netherlands, only a very small number of these animals has been observed in the wild, and therefore the question arose whether it would be feasible to reintroduce the European mink in the Netherlands with one of their major threats gone.
This project aims to study the possibility of the reintroduction of the European mink in the Netherlands based on the IUCN guidelines for reintroduction, to provide an outline and identify the knowledge gaps that need to be filled for a successful reintroduction in the future.
In general, most threats to the European mink have been mitigated. The presence of the American mink needs to be monitored closely, and its inability to settle in the Netherlands compared to other countries should be researched. The European mink is unlikely to pose a large risk to native Dutch biodiversity such as meadow birds, but is instead likely to consume invasive American crayfish species and aid in its control. There are several societal issues to overcome: the image of the general public of the European mink might be tainted due to COVID-19, and fishermen and trappers are likely to feel inconvenienced. Proper communication and support is necessary to ensure a long-lasting successful project.
The most suitable locations appear to be the Weerribben-Wieden and the Biesbosch, although their prey availability in winter months needs to be studied. A habitat suitability analysis needs to be conducted. The release of animals would have to occur over a span of multiple years, and to reduce the stress of travel in the animals, the best course of action would be to set up a breeding centre in the Netherlands. Each year pregnant females can then be placed in a soft-release enclosure, which can be opened up in August to allow the mothers and their young out in the wild.
More research is needed on proper monitoring methods, such as the suitability of radio-harnesses compared to intraperitoneal transmitters and the usage of scats for DNA analysis.
Die Bisampopulation in den Niederlanden ist durch Bekämpfung weitgehend unter Kontrolle. Nutrias wurden komplett aus dem Inland bis an die Landesgrenze zurückgedrängt. Der Grund für das intensive Bekämpfungsprogramm in den Niederlanden liegt primär in der Aufrechterhaltung des Hochwasserschutzes. Die wichtigsten Erkenntnisse eines Forschungsprogramms und die Organisation der Bekämpfung in den Niederlanden werden in diesem Artikel beschrieben. Der Schaden durch Grabaktivitäten an Ufern und Schutzanlagen ist größer, wenn mehr Bisame vorhanden sind. Der Schaden kann den Wasserschutz ernsthaft gefährden. Die Bekämpfung kann Auswirkung auf die Anzahl der Bisame haben, wenn genug Aufwand betrieben wird und die Organisation gut ist. In der niederländischen Situation halten sich die Kosten für die professionelle Bekämpfung auf nationaler Ebene die Waage mit dem Nutzen. Es gibt deutliche Hinweise, dass die Kosten der Bekämpfung letztendlich sinken, je kleiner die verbleibende Population wird.
For a good public debate on the pro's and contra's of muskrat control, it is useful to also weigh knowledge about the species and the numbers of by-catches. What factors affect the development of the number of by-catches? In this study we show that the number of by-catches from muskrat control in the Netherlands has fallen sharply in recent years. The number of by-catches depends mainly on the number of hours in the field (a proxy for the number of traps in the field). Apart from that there is a difference between control organizations, in interaction with the style of trapping. Our conclusion is that effective muskrat control can be seen as a suitable investment, in order to achieve less by-catches in the long term.
Voor een goede inhoudelijke discussie over muskusrattenbestrijding is het nuttig om feitelijke kennis over de soorten en aantallen bijvangsten in het debat mee te wegen. Welke factoren zijn op de ontwikkeling van het aantal bijvangsten van invloed? In deze studie laten we zien dat het aantal bijvangsten de laatste jaren sterk is gedaald. Het aantal bijvangsten hangt vooral af van het aantal uren in het veld (of het aantal uitstaande vangmiddelen), maar daarbinnen is er nog verschil tussen bestrijdingsorganisaties, in interactie met stijl van bestrijden. Onze conclusie is dat een effectieve bestrijdingsinzet kan worden gezien als een geschikte investering, om te komen tot minder bijvangsten op de lange termijn.
The dynamics of a muskrat population was studied from February 1970 to January 1972 on a fairly isolated stretch (7.5 km. long) of the river la Houille in South-Belgium, by capture-mark-release followed by a complete extermination on all of the hydrographis basin of the river.
Available online: http://www.ieep.eu/assets/448/ias_assessments.pdf
Europe has adopted innovative legislation on invasive species that could signal a step-change in the global response to biological invasion threats. The discussion that took place within EU institutions—EU Parliament, European Commission, and the Member States—permitted significant improvement on the initial proposal presented by the European Commis-sion, including removing the initial 50 species cap, explicitly allowing national authorities to take strin-gent measures on invasive species of national concern, and encouraging coordinated approaches to invasive species in boundary areas. An independent ''Scientific Forum'' to inform implementation has been intro-duced, and the EU Regulation will permit only limited licensing for specific activities using invasive alien species. However, the real strength of the legislation will largely depend on the decisions of a committee of representatives of the Member States, with the risk that the real enforcement will be limited by political and economic, rather than scientific, considerations. In this regard it will be crucial to set up a framework of roles and responsibilities among the different bodies that ensure transparent and objective decision pro-cesses. Also, it will be essential that adequate resources be secured for implementing the provisions of the legislation. Finally, the regulatory approach introduced by the Regulation will have only a limited impact unless European citizens raise their awareness of this threat and adopt more responsible behaviours.
Herein 6 criteria are suggested for deciding if eradication is technically possible and preferable to continuing control for managing vertebrate pests. The authors assess 3 case studies against the criteria. -from Authors
URN:NBN:no-2343 And you see that every time I made a further division, up came more boxes based on these divisions until I had a huge pyramid of boxes. Finally you see that while I was splitting the cycle up into finer and finer pieces, I was also building a structure. This structure of concepts is formally called a hierarchy and since ancient times has been a basic structure for all Western knowledge.
This chapter discusses the classes of problems for solution tools are discussed. It also considers the interrelationships between different problem classes as well as among the solution methods. In the real world, the objective function f() and the constraints c are not only functions of x but also depend on data; in fact, they may depend on vast arrays of data, particularly in statistical problems involving large systems. To illustrate, the chapter presents Cobb–Douglas and Hobbs' weed infestation examples, which illustrate some of the issues that will be encountered. There are some particular forms of the objective function that lead to specialized, but quite common, solution methods. This gives us one dimension or axis by which to categorize the optimization methods. Another categorization of optimization problems and their solution methods is via the constraints that are imposed on the parameters.