Are you experiencing problems with rats? You are not alone. While there is a stigma for having rats because most people associate them with filthy or dilapidated conditions, it’s not unheard of for rats to appear in homes or buildings that are pretty clean or fairly well maintained. Of course, there are preventative measures one can take to prevent a rat infestation, such as putting away all food material, and thoroughly cleaning and sealing any openings that would allow rats to access the building. But what if they have already made their way in, and now you are trying to figure out a way to get rid of them? The answer lies in a little science – but don’t run away! We will consider a three-part formula for effective rat removal: identifying rodenticides, figuring out the kinds of rats you are dealing with, and finding the best baits for that particular species. Put on your lab coat; for the first part of the formula, we’re going to do a light delve into the science behind rat poisons.
Rodenticides are chemicals that are fatal to rodents such as rats, voles, and others. There are two general types of rodenticides – anticoagulants and non-anticoagulants. Anticoagulants stop blood from clotting, causing internal bleeding. Non-anticoagulants use high doses of vitamins such as calcium or zinc to disrupt the delicate chemical balance in the rodent’s body. Many rodenticides are powerful, single-dose poisons that can only be sold to and used by licensed pest control professionals. This is because these powerful poisons present risks to non-targeted wildlife and humans and must be handled with great care. The rodenticides that you can buy in stores contain chemicals such as bromethelin, cholecalciferol, and warfarin (which you may know as a prescription drug used to treat blood clotting conditions in humans). These chemicals are called multiple-dose rodenticides, and we'll explain a little later why multiple-dose is good for residential application.
Knowing which poisons are effective and available is the first part of our formula for controlling rats. The second part involves identifying which rats might be infesting your home. In the United States there are primarily two species – the Norway rat and the Black rat.
Norway rats (Rattus norvegicus), also known as the sewer rat, the brown rat, and the street rat, are the more pervasive of the two species – meaning that if you’ve seen a rat, this was most likely the culprit. When people speak of “rats as big as cats,” they are speaking about Norway rats, which can reach a total length of 16-20 inches and weigh as much as two pounds! Norway rats can live almost anywhere and are known to overrun areas once home to black rats. They tend to burrow underground or to live on lower or subterranean levels, giving rise to their reputation as subway and sewer dwellers. They are tough, adaptable creatures, and while we view them as pests, they benefit their ecosystems as both predator and prey. Relevant to our discussion about rodenticides, Norway rats have developed a resistance to warfarin.
Black rats (with their very creative scientific name rattus rattus) are typically found in warmer, more coastal areas. They are also known as roof rats, ship rats, or house rats. They are considerably smaller than Norway rats, reaching lengths of about 10-15 inches with a tail longer than their body. Like Norway rats, black rats are omnivores and eat a wide variety of foods, although their preference is for fruits and nuts. As the name “roof rats” suggests, black rats prefer to live up high. In urban areas, they might nest in upper levels of buildings such as in attics and false ceilings. In the wild, they create round nests in tall pine or palm trees.
Rats are highly intelligent creatures, masters at learning and adapting. Anyone who has waged war with rats understands that they are clever enough to remove food without setting off a trap. This makes a multiple-dose rodenticide more effective. While we may want the quick action of a single dose to eliminate the rats as soon as possible, effective rat elimination is more of a long game. When a rat dies quickly after ingesting a poisoned bait, other remaining rats are intelligent enough to associate that death with the food that was recently eaten. Since rats also communicate with each other, they will teach each other to avoid the bait. This is less likely to happen with a slower- acting multiple-dose rodenticide. Since the rats have to eat the same bait at least twice, and the time between ingestion and death is a longer period, the rats are less likely to learn that the bait you are leaving out is poisoned.
Now we have two-thirds of our formula: the rodenticides you should look for and the kind of rat you may be combatting. The last piece of the puzzle is figuring out the most effective bait.
Bait is simply a toxic material mixed with an attractive food material. While the two common species of North American rats have a very similar diet, there are certain foods that are better suited to each of them.
Norway rats are primarily urban dwellers, and are used to eating a lot of human trash . When considering what to use as bait, think about things you might find in the garbage – peanut butter, nuts, dried fruit, gummy fruit drops, and even small pieces of bacon, hot dogs, and sausages!
Black rats tend to prefer a more natural, less processed diet of dried fruit, nuts or nut butter, and even slugs or snails.
Some experts suggest putting out small quantities of food without rodenticide for a few days. Why? It goes back to rodent intelligence. Placing out a tiny quantity of a variety of foods does two things: (1) it allows the rats to show you the food they prefer, narrowing down what to use as bait, and (2) it gives them a chance to sample until they learn that the food isn’t dangerous. When you add slow-acting rodenticide later on, the rats are less likely to associate the bait with poison. This also increases the likelihood that all the rats dwelling in the home will eventually eat the poison.
Mixing attractive food materials with the appropriate rodenticide and putting them into bait stations or traps is a highly effective way to lure in the rats. Tamper-proof bait stations, such as the ones sold by Eco Pro, are the safest option to prevent accidental poisoning when there are pets or small children present.
So now we have research-based answers to what makes an effective rat bait. Understanding the kind of rats you have, the foods that they are most likely to be attracted to, and the appropriate rodenticide will greatly increase your chances at winning the war against rats.