They need no more than a half-centimeter hole, says biologist Robin de Vries of the Animal Pest Knowledge and Advice Center (KAD). “As a general rule: if your fountain pen fits in it, your mouse will fit in it too.” Even mice squeeze through holes an inch or two apart. In short: introducing a mouse or animal into your home is not that hard. But how do you get them out again?
No more poison. On January 1, a law was passed banning the sale of rodenticides to individuals. More precisely, new packages of rat poison should not be put on the market. Until the end of June, shops are still allowed to sell old stock, which can be used until Boxing Day 2023. For example, the use of poisons is being phased out, among other things to improve animal welfare.
Slowly bleeding to death
Almost all banned toxins are anticoagulants, de Vries says. Blood thinners with names such as Brodifacoum, Bromadiolone, Chlorophacinone, Comatetralil, Defenacom, Diphythylone and Flucomafine. de Vries: “The result is that the animals slowly bleed to death from the inside.” In addition, the use of rodenticides based on cholecalciferol is also prohibited. Only one poison will remain allowed against house mice for now, also in new products: alpha-chloralose. “Unlike other substances, it’s an instant killer,” says de Vries. “A mouse that eats may lose consciousness after fifteen minutes and eventually die.”
On the other hand, anticoagulants are only fatal if eaten frequently by rodents. “The advantage of this is that bait shame occurs less quickly,” says de Vries. “If mice or rats see that a congener dies immediately after eating the grain or paste, they will not approach that food themselves.”
Another advantage is that there is an antidote to anticoagulants: If a child or pet accidentally gets poison granules from treats or kisses, they can be given vitamin K. De Vries: “Not that you’ll die immediately or else – after all, the doses are for small animals – but health is different.”
However, these blood thinners are now banned. One reason is animal welfare: slow bleeding to death means suffering. Potential resistance also plays a role. “If the poison is used incorrectly, then part of the population will survive. These are mainly the animals that react less sensitively to the poison. Then they produce offspring that also react less sensitively.”
Then there is the important issue of secondary toxicity, stresses Nico van den Brink, who, as a biologist and toxicologist at Wageningen University, has been researching the effect of anticoagulant rodenticides on ‘non-target species’ for years. These can be animals that eat the bait themselves, such as hedgehogs, but they are more often birds of prey, or hares or foxes that sometimes overtake a mouse or rat, and therefore can ingest poison. Van den Brink has written various research reports about it and was one of the authors of the book in 2017 Rodenticides and wildlife anticoagulants.
Researchers always find rat poison in dead barn owls
“We recently investigated thirty stone dead people who died as a result of road accidents,” says van den Brink. “We found anticoagulant rodenticides in twenty-nine of these.” He also regularly finds rat and rat poison in dead barn owls that are brought in for research. But you won’t find a great deal of poisoned animals, especially if they die from that poison. Because they often retreat to a hole or nest.
The death of a predator from eating a poisoned rodent depends on how much poison it ingested. Van den Brink: “Unfortunately, these substances do not decompose quickly, and so they can accumulate significantly in the food chain. Then birds of prey and predators can really suffer. For example, birds of prey may fly through the forest and catch wing by wrong, and anticoagulants may cause a much larger bruise than normal. Then they may not die from the rodenticide itself, but they may die from its consequences.”
The classic blow trap
To what extent domestic cats also fall victim to rat and rat poison by eating those animals, Van den Brink dares not say: “There has been no thorough research on this. But the mechanism of action is the same, so you can bet that they may also suffer from it.” “.
He stresses that, for the time being, he will continue to search for rodenticides on, among other things, field mice, martens and birds of prey. “The fact that the ban is in effect now doesn’t necessarily mean that you won’t encounter it anywhere. Everything can still be ordered on websites like Alibaba.”
If mice and rats can no longer be controlled with poison, how can you get them out of your home? The classic blow trap—a broken mousetrap with a mouse’s neck inside—is the best way to kill animals, according to both experts. A “mouse-friendly” trap, in which a mouse is caught alive and can then be released again, is in fact essentially a human-friendly trap, says van den Brink. “For a mouse, there are major drawbacks to such a trap cage. You are obligated to provide water, food, and shelter when using this trap, but many people don’t. Catching and releasing a rat causes so much stress that they often die.” The alternative is to get a cat – “even though it hurts the birds”. Crates for birds of prey are sometimes installed on farms.
Cavity walls and drainage
The most mouse-friendly solution, says de Vries, is prevention: “First and foremost, seal the holes in your house. But not with polyurethane foam, because they gnaw through it. It’s best to use steel wool or bee mouths. These are the nets you can put in in vertical joints of masonry.
The following also applies: Don’t leave any dishes out and put food in sealable containers. De Vries: “A mouse needs a few crumbs of bread a day to survive.” Van den Brink: “If you see one mouse, you have ten, is the general rule. And a mouse can have a litter of ten young several times a year, so things can quickly get out of hand.”
Van den Brink says it’s not just the population that is responsible for good prevention measures. Housing companies and municipalities also have to contribute, for example through maintenance of hollow walls and drainage. But it is rarely prioritized.”
in the right places
If you do not know what to do, you can contact a professional rodent exterminator. who does IPM, Integrated pest management. In short, this also comes down to prevention in the first place, says de Vries. “First, this barrier specialist looks at the living environment to see, for example, where the nesting sites or passages are. Then the traps are placed in the right places. In extreme cases, poison can be used. “They are culling poultry due to avian influenza. Executors must kill all rats and mice as quickly as possible, otherwise there is a possibility that the virus could mutate in those animals or spread through them.”
He stresses that hygiene is an important reason for fighting rats and mice anyway. “In the United States there is a hantavirus, which sometimes kills people. This is not the case here yet, but what is new is different.” Another danger, van den Brink says, is that they’ll chew through the cables. On farms, stable fires sometimes occur because wires are affected by rat damage.
A completely mouse-free environment, de Vries says, is an illusion. “Mice and rats are omnivores of culture, and those creatures follow people everywhere because we inadvertently create hiding places, nesting places, and food facilities for them. But you can limit the nuisance they cause without using poison.”