Avian vampire flies (Philornis downsi) were not discovered in the Galápagos Islands for almost three decades after they were thought to have arrived from mainland Ecuador in the 1960s. Even then, the first were found by accident.
Birgit Fessl, a landbird ecologist, was surveying for native species on the island of Santa Cruz in 1997 when she reached into the branches of a tree to take down the huge, domed nest of a woodpecker finch. Inside was a surprise. “We found one dying chick, another dead one which just looked sucked dry and 20 large maggots full of blood,” said Fessl, who now leads the Charles Darwin Foundation’s Landbird Conservation program.
“I was stunned — the first dead baby in my hands. Then I realized it wasn’t an accident: It was everywhere,” she told Mongabay over a WhatsApp call. Across each of the Galapagos’ human-inhabited islands, vampire flies had already wrought havoc, killing some chicks in nests they infiltrated and leaving others maimed for life. “But it went unseen because people didn’t really know what to look for.”
Around the world, more than 37,000 invasive species have been introduced to new environments. Many of these cause suffering, from vampire flies maiming finches to yellow crazy ants (Anoplolepis gracilipes) spraying acid at the eyes of shrikes (Laniidae) on Minami-Daitō Island, Japan, and Australian quolls (Dasyurus) bleeding from the nose after eating toxic cane toads (Rhinella marina). But none of these are measured by the current global standard for assessing the impact of species invasions, which looks at the severity of their environmental impacts.
In a study published in early May, an international team of researchers set out a new framework to quantify the impacts of biological invasions on animal welfare. Testing it across hundreds of examples of bird and ant invasions, they found that the framework produces consistent results. Additionally, the trials found that certain invasive impacts (particularly the suffering inflicted by smaller invasive species) are overlooked by existing frameworks that focus on biodiversity or economic impacts. By measuring welfare impacts, conservationists also need to consider the suffering of invasive species themselves.
“Hopefully it will shed light on a whole topic that is completely neglected,” said Thomas Evans, a biologist at the Free University of Berlin, who co-designed the framework with Michael Mendl, a professor of animal behavior and welfare at the University of Bristol. “Lots has been done on the biodiversity and socioeconomic impacts [of invasions]. This is a third, related framework for animal welfare,” said Evans, who helped formalize the existing, U.N.-approved measure for biodiversity impacts.
The Animal Welfare Impact Classification for Invasion Science (AWICIS) framework asks academics and conservations to weigh several indirect indicators of suffering (physical, behavioral or psychological) alongside how that suffering is inflicted (from parasitism and direct predation to competition for resources) and for how long. The final impact score is also adjusted according to how confident researchers are in their grading.
Kevin Smith, head of the IUCN’s invasive species and wildlife health program, said the new framework promises to be “a useful and practicable tool” if the conservation community adopts it. “Overall, I think it’s a really interesting and potentially useful approach,” Smith said, “that should support engagement and awareness raising with the public and decision-makers.”
The framework joins a recent wave of research attempting to quantify animals’ suffering, though much of this has focused on livestock. Those considerations should be extended to wild animals, too, Evans told Mongabay over video call. “We’re the driver of these introductions, so we have a moral responsibility to put them right. To protect animals, not just in terms of species survival, but also in terms of their suffering.”
Michaël Beaulieu is a vet and behavioral ecologist from the University of Strasbourg in France and research manager at Wild Animal Initiative, which funded the development of AWICIS. He was also one of three researchers to help test the framework on five trials and then on 10 case studies. Beaulieu was able to assess five examples per day, he told Mongabay over video call, and the process was at first “an intellectual effort.”
“I made several errors, but that makes sense as I familiarized myself with the framework. … It was still able to generate consistent results across assessors,” he told Mongabay. Beaulieu and other testers were asked to scan for welfare impacts across unfamiliar research papers describing biological invasions; he and Evans expect the framework to work more efficiently for academics or conservationists inputting their firsthand knowledge of species interactions.
The framework’s authors acknowledged that relying on existing academic literature describing biological invasions skewed their measurement of suffering away from lower-income regions toward islands, where invasives are more keenly felt and, therefore, often more rigorously observed. Nonetheless, initial case studies revealed some blind spots in existing systems for measuring invasive impacts and potential conservation responses.
“It sheds more light on the fact that small species can cause severe welfare impacts: looking out for the tiny guys like ants and flies would be extremely important in the future,” Evans said.
AWICIS also flags welfare impacts long before an invasion might affect biodiversity. “With welfare, impacts can occur as soon as an alien species is introduced. So, the emphasis is far more on preventing them from arriving in the first place,” as opposed to mitigation measures, Evans said.
Smith agreed that AWICIS “does fill a gap” in how invasive impacts are measured but was less convinced that it would shift conservation decision-making. “I don’t think it will change resource allocation away from environmentally harmful biological invasions towards those that may have greater welfare impacts,” he said. But “any evidence that prioritizes prevention is good for me — and is good for the environment, our economies and well-being.”
For Beaulieu, the immediate importance of AWICIS is as much in shifting perceptions about relationships with wild animals as in influencing conservation strategies. “Most conservation decisions are [nominally] made for the benefit of wild animal populations but also indirectly for humans. We’re thinking in terms of ecosystem services, what can we take from them,” he said.
“This framework has nothing to do with human benefits at all. It’s a pure sentientist perspective. The animals have their own interest, and that should be respected irrespective of human interests,” he added. “You might agree or disagree about priorities, but this research shows [welfare issues] at least exist and are something to consider.”
In the Galápagos, Fessl and other researchers were ultimately able to bring attention to the impact of vampire flies without a welfare metric because the invasives killed enough birds to affect population numbers. AWICIS, nonetheless, looked like a “really good” system and might have brought the situation to the fore more quickly, Fessl said.
But measuring the welfare of invasives themselves could also put conservation work itself on “slippery ground,” Fessl said. In the past decade, conservationists have begun “self-fumigating” vampire flies with insecticide-treated cotton wool left for birds to incorporate in their nests. AWICIS does not currently measure invertebrate suffering, but if it did in the future, Fessl worried it might show that self-fumigation caused suffering for the flies themselves.
“Do you improve the situation or do you cause even more suffering?” Fessl asked. “It’s not an easy answer, whatever you do.”
