Rat poison threatens wildlife in Catalonia

Saint Perpetua of MogodaIt's just a few minutes past nine in the morning, and the center's soundtrack is constant howls, flapping wings, and chirping. It's the end of July, and a new heat wave is already in sight. "Today I have three necropsies and several urgent cases to attend to," Rafael Molina tells us as soon as we arrive, gesturing for us to join him. "Where would you like to start?"

We're at Torreferrussa, the wildlife recovery center located on the outskirts of Santa Perpètua de Mogoda, in the Vallès Occidental region. The veterinarian guides us through the facilities toward the consultation area and operating room. Before that, we pass through a series of rooms where russet eagle-owls, black-backed eagle-owls, harriers, and even a beautiful dun-eared owl with orange eyes and a hypnotic gaze are recovering. Further along, in a room, two volunteers patiently feed hoopoe chicks, bee-eaters, and birds found in the wild one by one: most of them have fallen out of the nest or are injured. They also have some hedgehogs. Molina enters the room directly across the hall, and we follow him because there, inside a cloth-covered incubator, is the chick we've come to meet today.

They found him and a brother in the nest three days ago, their neck feathers dirty and bloody, and in very poor condition. Rural police suspected food poisoning and quickly transferred them to Torreferrussa, a pioneering center in Spain for the recovery of birds of prey and also one of the centers in the world with the highest intake of animals, around 15,000 a year. Here they are treated, operated on if necessary, and do everything possible to save them and release them back into the wild.

Molina lifts the cloth, and we see the tiny Egyptian vulture for the first time, looking at us anxiously. "It has a very friendly face," the vet says, and we can't help but nod. What a privilege to be able to observe this bird up close, which in the wild we must content ourselves with observing from below and through binoculars. Then Molina opens the incubator door and gently picks it up. Although she places it on the table, the animal barely moves; it still can't fly, and its strength is failing it.

The chick is part of a repopulation project for these small vultures in the Alt Empordà region. They had previously bred naturally in the Girona region, but had ended up disappearing for various reasons. Four years ago, a plan was launched to reintroduce them.

"When we started we didn't have any pairs and this year we have two," ornithologist Jordi Sargatal, current Secretary of Ecological Transition for the Generalitat (Catalan Government), proudly explains to us over the phone. "The first pair already bred in 2021 and the second had done so in 2025," he adds. The chick in front of us is one of the chicks and in its short lifespan it has already been on the verge of death.

In the nest, the rural agents also found remains of rats, probably from the Pedret i Marzà landfill, located on the Figueres to Llançà road, where the adult Egyptian vultures, geolocated with GPS, frequently went to eat and provision themselves.

"The blood on the neck and the rodent remains suggested they might have been poisoned by rodenticide," Molina explains, although she can't confirm the diagnosis until the results from the toxicology lab arrive.

At landfills, populations of rats are often controlled with rodenticides, anticoagulant poisons that cause death by hemorrhage within two or three days. They are highly effective, but also poorly selective. The consequence is that they collaterally affect many other wild species, some of which are in a very critical situation.

Birds of prey, such as the Egyptian vulture, the kestrel, and the dun, are among the most affected because their primary diet is rodents. Some small carnivorous mammals, such as ferrets, martens, foxes, and vultures, are also poisoned.

"The use of rat poison is a very serious problem for wildlife," laments Sargatal, who also questions its use: "By undertaking it, we are helping to eliminate the enemies of rats, those that eat them and could help them naturally control it.

Meanwhile, in Torreferrussa, Molina continues to check the little Egyptian vulture: he weighs it and checks, relieved, that it is gaining weight; then he gives it vitamin K - the antidote for anticoagulants - and feeds it by dropping raw meat directly into its crop. The chick swallows it without complaint. "I think it will pull through," the vet says softly, optimistically.

Legal products

Rodenticides are legal products authorized to control the population of rodents, rats, mice, and voles. They are used in humanized areas, such as cities—the tubular black boxes are frequently seen on trains and subways, for example—farms, and housing estates, where these animals are thought to be capable of causing potential damage.

"There is a European pesticide directive that allows them and that has been extended," says Joan Real, a professor at the University of Barcelona and also a researcher atBiodiversity Research Institute (IRBio)Although in 2018, in response to the evidence of the damage they cause to biodiversity, a legislative change was made in the European Union to reduce their concentration in baits, the impact on wildlife has not improved. This is likely because people believe they are less effective and use more of them.

The problem is that they spread to the food chain and pose a serious danger. "In Catalonia, we have an endangered mustelid, the European snail, which has been disappearing for the last twenty years. In specimens found dead, autopsies have revealed lethal doses of anticoagulants," warns Real.

They have been used for decades: the current, second-generation ones are administered in small doses, mixed with seeds or some other food attractive to rats. However, many other animals end up in contact with the poison, which has been detected in insects, snails, slugs, and even freshwater fish.

"Bait tablets can be consumed by many invertebrates. Rodenticides don't affect them, but they can be passed on to insectivorous species, such as hedgehogs," she points out. Rafael Mateo, researcher at the Institute for Environmental Diagnosis and Water Studies (IDAEA-CSIC), a research center located in Barcelona.

In fact, this biologist already published a study in 2015 concluding that in Catalonia, nearly 60% of hedgehogs were contaminated by rodenticides. In another study conducted with wild boars killed by hunters in Barcelona, ​​they found 50% of the animals. "If you look for rodenticides, you'll find them practically everywhere," says Mateo.

2007, a turning point

The highly harmful impact of these chemicals on wildlife has been known since the late 1980s, when the UK's Centre for Ecology and Hydrology Research documented how barn owls died from poisoning rats ingested with rodenticides. Since then, hundreds of scientific papers have been published warning of the danger of these biocides to biodiversity and have linked them to the decline of many carnivorous species.

In this sense, what happened in Castilla y León in 2007 marked a turning point in the use of rodenticides in Spain. That year, they were used massively to put an end to an overpopulation of voles, small rodents related to lemmings and muskrats that eat crop roots and make holes. These types of pests are cyclical, Mateo explains, occurring every two to five years, and naturally bring with them many species of nomadic birds of prey that follow them around the territory to feed and breed.

"In a vole's beak, it's common to find specimens of the European hawk, Montagu's harrier, migratory owl, and even the hen harrier, which is a very rare species native to the steppes of Siberia," Mateo points out.

Well, in 2007, farmers decided to apply a very intensive treatment of rodenticides to eliminate these small rodents. "The Regional Government of Castilla y León distributed tons of rodenticides that were spread on the fields with the fertilizing machines," Mateo explains. As a result, they had massive deaths of hares, breeding pigeons, hedgehogs, sheep, and many other animals. All of this led to their removal from the list of phytosanitary products suitable for agriculture in Spain. For this reason, now "they cannot be used to protect crops, but only as biocides to protect assets of human interest, such as buildings, farms, and subway cars," explains Mateo.

However, this expert complains, the problem is that in Spain there are many homes scattered throughout the country, very close to the countryside, and these products continue to be used intensively. Furthermore, remember, wildlife is much closer than we imagine. "Right now, from my office on Diagonal, I can see a peregrine falcon nest," notes the IDAEA researcher.

Why aren't they banned?

If the negative impact on biodiversity has been proven, why aren't they banned? The answer: "Rodents are a public health problem, and although alternatives have been investigated, they are not as effective at the moment and are more expensive," says Mateo. One is coliciferol, which causes damage to blood vessels and also hemorrhages, and does not appear to be transmitted up the food chain. Genetic treatments are also currently being researched to modify populations and prevent reproductive failure.

From the Generalitat (Catalan Government), Sargatal announces that they will carry out an awareness campaign so that people stop using it indiscriminately. Since they are not regulated, he states: "We want to find other ways to control pests and then we will adapt Catalan regulations." It should be, says Sargatal, a priority for the Catalan Government. And, to begin with, he explains that he is working with the Catalan Waste Agency, which controls the country's public landfills, to stop using these toxic products.

For Real, we should also reconsider when rodents truly pose a danger. "Humans tend to be intolerant," he emphasizes. It's normal, he adds, for rats and mice to exist: perhaps even if they are abundant, he argues, there's no need to act. And he advocates taking preventative measures. The best, he agrees with Sargatal, are natural ones. In the past, they recall, cats lived in every house and farm, eliminating this problem at its source. Another option is birds of prey. The Wildlife and Habitat Rehabilitation Group (GREFA) It has shown, for example, that rodenticides can be avoided by installing nest boxes to increase the population of owls, barn owls, and kestrels, achieving effective control of rodent pests in rural areas.

Real insists that, in the case of farms, "many have rats due to a lack of cleanliness." "It's clear that if you have feed scattered on the floor and everything is dirty, you encourage the presence of these animals," he adds.

The Duke, a sentinel species

This biologist from the UB had been observing for some time that the Duke (Bubo bubo), the largest owl in Eurasia, had almost disappeared from the Plana de Vic. In fact, in previous decades "the population had been declining sharply throughout Europe and in our country it had become extinct in the Pyrenees, the Pre-Pyrenees and many regions of Central Catalonia. However, they had begun to be seen in areas such as the Vallès region.

To understand why the owls were abandoning wilder, well-preserved areas and moving toward human-dominated areas, he launched a project in collaboration with Rafael Mateo to monitor individuals with sensors placed in nests and GPS devices attached to chicks. "We wanted to find out what areas they occupied, where they hunted, and where the lice that hatched went," explains Real.

This is when they began to realize that mortality was very high in both young and adult specimens. "This affects the viability of the population, which here on the plain has been declining significantly. This year we are at the lowest population level ever seen in at least the last ten years," the biologist laments. And one of the most important causes of mortality they have identified is rodenticide poisoning.

"When we started looking at the livers of wild animals that arrived injured or dead at Torreferrussa, we were able to grasp the magnitude of the tragedy: 90% of the dukes they brought in had lethal levels of anticoagulants. And that's just the tip of the iceberg."

So far, they've analyzed at least thirty adult dukes, and the vast majority had high doses of rodenticides. Now, Real explains, with competitive funding from the government of Castilla-La Mancha and the Ministry of Ecological Transition, lice are being sampled in Catalonia. "We have about 300. We go to the nests, take a blood sample, measure them, and we're seeing that a significant percentage of the young, at 30 days old, already have anticoagulants with lethal doses," he explains. The problem with rodenticides, Mateo adds, is that it's a phantom death; if you don't analyze the animals, you don't know what they died of. The Royal Family emphasizes the importance of the project they are developing with the Duke and Duchess. "It's necessary for people to be aware of the damage these poisons cause."