“Thar’s rats in them thar slums!” might replace, “There’s gold in them thar hills!” as the rallying cry for the U.S. State of California.
The Golden State is dealing with large groups of homeless people living in filthy tent cities, cardboard boxes or on the open street, often with no sanitary facilities or even trash cans for waste disposal.
Piles of rotting garbage and uncovered human waste are attracting and harboring rats and other scavenging vermin, especially in parts of major metropolitan areas such as Los Angeles and San Francisco.
The rats in California do what rats everywhere else in the world do: they are born, eat and breed voraciously, and die. The brown rat (Rattus norvegicus), also called the common rat, street rat, sewer rat, water rat or wharf rat, can breed throughout the year under the right conditions. One female can produce up to five litters a year of up to 14 young, although seven is common. The gestation period is only 21 days.
All those facts boil down to this staggering statistic:
A rat population can grow from 2 to 15,000 in a single year!
The good news, if you could call it that, is the longest a brown rat can live is three years, although, with a yearly mortality rate of 95%, most don’t make it to their second birthday. Predators and interspecies conflict are accountable for most rat deaths.
American gangsters are famed for calling each other, “You dirty rat!” but the truth is that rats are hairy mammals and, like any such creature (including us humans), they pick up dirt from their environment. The average pest rat is indeed, literally, a dirty animal – but only because its habitat is often sewers and its food source is often garbage.
The real danger to humans from wild animals, including rats, is from bites which can spread various diseases and from parasites (fleas and mites that harbor deadly pathogens) they carry on their bodies which jump from them onto us.
Rats also contaminate food and water with their fur, urine, and droppings, causing some serious diseases, including typhus.
Just about everybody agrees that brown rats need to go “quietly into the night” of eternal sleep – but not everyone supports the same way to go about it.
Humans have spent countless years puzzling over how to build “the better mousetrap.” Rats are considered to be rodents and they are instinctually wired for self-preservation. As such, they can be surprisingly difficult to catch, especially in large enough numbers to make a difference in keeping the total population low.
Pest control professionals are experts in trapping live animals, either for relocation or instant dispatch. But poisoning is another way to solve a rat problem.
California is in the headlines because of a new bill (AB 1788) proposed by state legislators. The bill is titled, “Pesticides: use of anticoagulants,” and, as of the first week of August 2019, AB 1788 has passed the first two committees of approval and is now awaiting the final committee’s approval before becoming California law.
The pending West Coast bill, dubbed the “California Ecosystems Protection Act of 2019,” is controversial because it would prohibit the use of the most effective poisons, termed rodenticides, against rats.
Why would anyone do that, you ask? The answer is simple: anything that can kill a rat can, in a big enough dose, kill a person – or anything that eats a rat tainted with toxins.
At risk from secondary exposure to rodenticides, then, are all the animals that prey on rats, from wolves, foxes, hawks, owls, and snakes to your pet tabby Brutus – and you!
Worse, these toxins hang around in the bodies of the animals that consumed them. Eventually, the poisons set out by humans to kill pest-ridden rats eventually get washed by rain into streams, aquifers, and groundwater.
Rodenticides generally come in two main types: anticoagulant or non-anticoagulant. Anticoagulant rodenticides cause internal bleeding and prevent the blood from clotting. After consuming a lethal dose of poison, the animal dies from internal bleeding complications. Non-anticoagulant rodent poisons have toxic effects on different organs and to varying degrees.
Anticoagulant rodenticides are further classified as either first-generation or second-generation. It takes several consecutive feedings for a lethal dose of first-generation anticoagulant rodenticides (FGARs) require to accumulate. Currently, the U.S. Environmental Protection Agency (EPA) lists three registered FGARs: warfarin, chlorophacinone, and diphacinone.
Second-generation anticoagulant rodenticides (SGARs) were developed after rats developed resistance to first-generation compounds that occur naturally in mice and rats. As a result, SGARs are much more toxic and can cause death in one feeding. The EPA lists approved SGARs that include brodifacoum, bromadiolone, difethialone, and difenacoum.
After exposure, the body is able to excrete FGARs easily and quickly so that, without continuous or repeated consumption of the poison, a lethal dose is difficult to accumulate. In contrast, SGARs are very difficult for the body to excrete and repeated feedings are not needed to build up to a lethal dose.
The potential for single-dose lethality of SGARs makes them extremely dangerous and high risk for causing unintentional secondary poisoning.
On July 1, 2014, the California Department of Pesticide Regulation (DPR) reclassified SGARs so that only licensed pest control professionals can purchase and use rodenticides containing brodifacoum, bromadiolone, difethialone or difenacoums.
If passed, California’s Assembly Bill #1788 would be the first in the nation to institute a complete ban on SGARs and ban FGARs on state-owned land.