Extended use of rodenticides has lead to resistance for London's mice

The argument

Mice have always been prevalent in London, and given the city's longevity they have had countless generations in which to adapt to their surroundings. The speed of those generations is what makes the adaptation possible: mice reproduce quickly, and a single female can have up to 10 litters per year with 5-6 mice per litter. A population turning over that fast can change its characteristics within a human lifetime, which is the precondition for everything that follows. The pattern of poisoning and recovery is the standard mechanism of resistance, observed here in the open. As people began to fight the mouse problem with anticoagulant rodenticides in the 1940s and 50s, the population was initially reduced to a fraction of its former size. But a poison that kills most of a population does not kill a random sample of it — the survivors are disproportionately those least affected by it. Scientists observed in the 1960s that the mice remaining after the use of these rodenticides had developed an immunity to the poison, including genetic mutations that protected them, and those survivors quickly reproduced. Because the poison had removed their competition, the resistant mice inherited the city, and with that reproductive rate their descendants replaced the population within a few decades. The same thing then happened again with a later-developed compound known as bromadiolone, which is what shows the outcome to be a general consequence of the method rather than a problem with one chemical. Each new poison repeats the cycle it is meant to break. The result is a mouse population in London that is mostly immune to the anticoagulant rodenticides previously relied on — a population shaped by the very effort to eliminate it.

Context

Traditional rodenticides are typically anticoagulants, which kill mice and other rodents through excessive internal bleeding. While there are other types of poisons--not to mention other methods of controlling mice populations--anticoagulant rodenticides are some of the most commonly used.

Premises

Counter-arguments

Saying that mice are resistant to rodenticides is oversimplifying the matter because there are many poisons, even anticoagulants, that can be very effective in controlling mouse populations. Just because London's mice are now resistant to some compounds like Warfarin and bromadiolone does not mean that this fully excuses or explains the city's current mouse problem.

Rejecting the premises

[Rejecting P1] Selection acting on survivors is the right mechanism, but the premise gives no figure for how much of London's mouse population actually carries resistance — rapid breeding explains how a trait spreads once present, not that it is now prevalent. [Rejecting P2] Anticoagulant resistance was first characterised in rats, and the later compounds were developed precisely to overcome it, so as the counter notes resistance to two named poisons does not show that rodenticides in general have stopped working — and none of it touches the sibling positions on waste, buildings and the size of the city.

Further reading

More on mice: https://bpca.org.uk/a-z-of-pest-advice/mouse-control-how-to-get-rid-of-and-prevent-mice-bpca-a-z-of-pests-/189003#the-dangers-of-mice Rodenticide Resistance Action Group (RRAG): bpca.org.uk/about/partners/rrag