Biological invasions occur when organisms such as animals and plants are introduced to regions of the world where they do not naturally occur. It's already known they can be severely harmful to biodiversity, for example by causing the extinction of native species, and they can also affect human health and wellbeing, by spreading diseases to people or by hindering agricultural activities. In fact, the impacts of biological invasions on biodiversity and people have been studied for many years.
In this study, the researchers have developed a new framework to assess how biological invasions affect the welfare of individual animals, providing a structured way to identify and compare impacts such as injury, stress, and behavioural disruption.
The framework, called the Animal Welfare Impact Classification for Invasion Science (AWICIS), was applied to existing studies of invasions involving birds and ants, two globally widespread groups with very different types of impacts.
The study found that invasive ant species frequently cause severe welfare impacts wherever they establish, while introduced bird species have less severe effects. However, the researchers caution that many impacts are underreported, particularly those affecting introduced animals themselves.
Tom Evans, Research Fellow in Biodiversity and Animal Welfare in the Bristol Veterinary School, and co-author, said: "Using AWICIS, we show that the animal welfare impacts of biological invasions are a global phenomenon - they can cause the widespread suffering of animals, and in some cases this suffering is severe. Indeed, some ant species tend to cause severe welfare impacts on animals wherever they are introduced."
Mike Mendl, Professor of Animal Behaviour and Welfare in the Bristol Veterinary School, and co-author, added: "Poor welfare and suffering, including in wild animals, can be inferred from changes in certain physical and behavioural signs. Examples include injuries, stereotypic self-damaging preening behaviour, and injurious aggressive behaviour.
"While physiological data such as immune markers and stress hormone levels are less commonly collected in studies of wild animals, they could provide valuable additional insight into the severity of welfare impacts."
The researchers suggest that existing studies on biodiversity impacts represent an untapped resource for understanding animal welfare consequences. By integrating welfare assessments into invasion biology, the framework could help conservationists, policymakers, and animal welfare scientists better evaluate the full costs of invasive species.
The findings could be used to identify vulnerable animals that require protection from the welfare impacts caused by biological invasions. The research suggests that improving global biosecurity is crucial to prevent biological invasions and the animal suffering they cause.
The researchers hope the study will encourage greater consideration of animal welfare in environmental management decisions and encourage further research into the hidden suffering caused by biological invasions. AWICIS is a publicly available tool that can be used by research scientists who wish to assess the animal welfare impacts of biological invasions.
Paper
'Quantifying and categorising the animal welfare impacts caused by biological invasion' by Thomas Evans, Michael Mendl in Nature Communications [open access]
