Investigator(s): Dr Sandra Baker
The aim of this work was to assess the relative welfare impacts of six rat management methods in order to inform reduction of welfare impacts in rat management. The methods were snap trapping, cage trapping with concussive killing, glue trapping with concussive killing, anticoagulant poisoning, cholecalciferol poisoning and cellulose baiting.
Millions of rats are killed globally each year in an effort to protect human health, food supplies and property and there are concerns about the impacts of rat management methods on rat welfare. There is growing recognition that where people negatively affect the welfare of wild animals they should act to minimize welfare impacts where possible. In order to do that it is necessary first to establish the relative impacts of different methods and to examine the kinds of impacts concerned.
Dr Baker conducted a welfare assessment project involving: preparing a Standard Operating Procedure (SOP) for each method explaining precisely how each method should be applied according to best practice; reviewing the literature on known and likely welfare impacts of each method on rats; establishing a team of experts in rodent management, rodent biology, animal welfare science, veterinary science and wildlife management (from the UK, Germany, Australia and New Zealand); facilitating two online stakeholder workshops and encouraging discussion to reach group consensus on scores.
The greatest welfare impacts were associated with the three baiting methods, anticoagulants, cholecalciferol, and non-toxic cellulose baits (severe-extreme impact for days), and with capture on a glue trap (extreme impact for hours) followed by concussive killing (mild-moderate impact for seconds to minutes). Lower impacts were associated with cage trapping (moderate-severe impact for hours) followed by concussive killing (moderate impact for minutes). The impact of snap trapping was highly variable (no-extreme impact for seconds-minutes).
Given our findings, rat management may represent the greatest anthropogenic impact on wild animal welfare. Anticoagulants, cholecalciferol, cellulose baiting, and glue trapping should be considered last resorts from a welfare perspective. Snap traps are currently unregulated in the UK and elsewhere except Sweden; snap traps should be regulated and tested to identify those that cause rapid unconsciousness; if such traps are identified then they could potentially represent the most welfare-friendly option assessed for killing rats.
These results can be used to integrate consideration of rat welfare into the selection of management methods alongside other factors, including efficacy, safety, cost, public acceptability. The findings also highlighted ways of reducing the welfare impacts associated with different methods and identified areas where more data is needed.
Animal Welfare, 27.01.22: An assessment of animal welfare impacts in wild Norway rat (Rattus norvegicus) management