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How To Make Safe and Effective Rat and Mouse Baits Using Baking Soda


Introduced, non-native, feral rodents, such as the Black Rat (Rattus rattus), Brown Rat, aka Ship Rat or Norway Rat (Rattus norvegicus) and House Mouse (Mus musculus) are serious pests that need to be controlled.

The danger with using commercial poison baits to control rats and mice is that pets or native wildlife (mammals and birds) that normally eat rats and mice can be harmed. Other vertebrate species, such as reptiles and amphibians are also at risk by eating dying rodents.

Rather than risk pets and wildlife, a better option is to bait rats and mice using a environmentally safe, home-made bait that uses bicarbonate of soda (baking soda). This exploits a unique feature of rat and mouse biology, their inability to burp or vomit, to create an effective rodent control.

Rodent Damage to Homes and Gardens

Rats and mice are serious pests that can severely damage a garden. They will eat a range of food crops, and also chew through protective nets that are put in place keep other pests out.

Fruit tree netting damaged by rat

Inside the home they may spoil and contaminate food, physically damage structures and furniture by gnawing on them, and also damage electrical wiring which may start house fires.

Why Are Rats and Mice A Health Hazard?

Rats and mice live in unhygienic environments, and have the potential to transmit diseases to humans, posing a health risk.

The most common disease transmitted by rats and mice is Salmonellosis (infection with Salmonella bacteria) through the consumption of food contaminated by rodent saliva or droppings (faeces).

They can also spread many other diseases through food or drinking water contaminated via rat urine, droppings , saliva, hair, as well as by breathing dust contaminated with their urine and droppings.

How to Make Rat and Mouse Bait With Baking Soda

When rodents eat baking soda (bicarbonate of soda), it reacts with their stomach acid to foam up and release carbon dioxide gas, which has nowhere to go because they cant burp! That’s how it works.

Sodium bicarbonate, also known as bicarbonate of soda or baking soda (NaHCO3) is an odorless white crystalline powder or granules. It has a saline (salty) and slightly alkaline (bitter) taste. It is alkaline with a pH of 8-9, and decomposes around 50 °C (122 °F). It is non-toxic, and is typically used as a leavening agent, which means it is used to help baked goods rise.

Since rats and mice wont eat baking soda on its own, we need to mix it with other ingredients that are appealing to them. Here are two recipes which work well.

Peanut Butter and Baking Soda Rat Mouse Bait

Peanut butter is really attractive to rodents, perhaps because it’s such a rich food. It’s sweet, contains fats and oils, protein, and has a strong smell!

Ingredients required:

To make this peanut butter rodent bait:

  1. Pour equal parts peanut butter and baking soda into a small container, and mix it well. A few heaped teaspoons of each will make enough bait.
  2. Spoon the mixture onto a small disposable saucer such as a plastic jar lid, cut down plastic bottle or milk carton.
  3. Place the bait along walls or between spaces where rats frequent, and leave the baits in the same location for a few days, as rats are shy and may inspect the bait but not it it until it feels it is safe.

Flour Sugar Chocolate and Baking Soda Rat Mouse Bait

This rat and mouse bait recipe uses a mix of ingredients to form a dough that is attractive to them.

Ingredients required:

To make this flour, sugar and chocolate rodent bait:

  1. Pour equal parts sugar (either white sugar of castor sugar), flour, and baking soda into a small container, add a little chocolate powder or chocolate sprinkles for extra flavour, and mix it well. The chocolate is optional, but it makes the bait far more enticing!
  2. Add a very small amount of water into the mixture, and stir it in, adding a little at a time until a fairly firm dough is created.
  3. Spoon the mixture onto a small disposable saucer such as a plastic jar lid, cut down plastic bottle or milk carton.
  4. Place the bait along walls or between spaces where rats frequent, and leave the baits in the same location for a few days, as rats are shy and may inspect the bait but not it it until it feels it is safe.

Where to Place the Rat and Mouse Baits and How to Handle Them

Rats and mice have poor vision, but they’re very cautious, so they tend to move from place to place along walls or other runs, away from wide-open areas. It’s best to place two or more baits around 2m apart along these ‘rodent runs’.

They have excellent smell though, and will reject anything that has human scent on it! Wear gloves when handling containers for baits, baits and traps, and wash the containers first to get rid of any human smell.

Why Rats and Mice Cant Burp or Vomit!

Say again, I can’t do what???

Vomiting is a protective reflex to rid the body of ingested toxins. Rodents (such as rats, mice, rabbits and guinea pigs) can’t vomit, due to a combination of factors related to their physiology and neurology, which prevents them from doing so.

The physiological (bodily constraints) that limit vomiting include a reduced muscularity of the diaphragm (the thin sheet of muscle underneath the lungs), and a stomach that is not structured well for moving its contents back up the throat.

Specific neural circuits are involved in the reflex of vomiting. It is believed that vomiting is controlled by two distinct brain centres, the vomiting centre and the chemoreceptor trigger zone (CTZ), both of which are located in the medulla oblongata. The medulla oblongata is part of the autonomous central nervous system that directly connects the brainstem with the spinal cord, and is located at the base of the brainstem.

When researchers investigated the brainstems of lab mice and rats, and gave them vomit-inducing drugs, compounds that normally trigger nausea in other animals, the researchers saw less nerve, mouth, throat and shoulder activity normally associated with vomiting, suggesting that rodents lack the brain circuits for throwing up.

This is the reason why rat and mouse poisons works so well, once they ingest the toxic bait, they can’t vomit it back up to expel it from their bodies.

Rodents have evolved alternate ways to avoid ingesting or absorbing toxins though. They respond to the taste of what they’re eating to avoid toxins that can make them sick or kill them. If they’ve ingested something and are feeling unwell, they will eat clay to absorb the toxins, preventing their bodies from absorbing them. Pica, the eating of non-nutritive substances such as kaolin (clay), is an illness-response behavior in rats that is analogous to vomiting in other species, which may be mediated by the same mechanisms as vomiting in humans.

How Much Baking Soda Do Rats and Mice Need to Eat?

The LD50 (which stands for Lethal Dose 50%) is a measure of acute toxicity, and refers to the amount of a poisonous substance needed to be lethal to half of the test population.

From Sax’s Dangerous Properties of Industrial Materials. 11th Edition, we can find out how much baking soda will be lethal to 50% of a group of rats or mice from the figures below:

If we consider that the body weight of a mouse ranges from 17-25g, at 3,360 mg/kg or 3.36 mg/g of body weight, it would take between 57-84mg of baking soda to eliminate half of the mice tested, and much more to eliminate all of them.

Rats are much larger, the body weight of a rat ranges from 200-500g, at 4,220 mg/kg or 4.22 mg/g of body weight, it would take between 72-105mg of baking soda to eliminate half of the rats tested, and much more to eliminate all of them.

In the recipes, the baking soda is either 1/2 or 1/3 of total ingredients, so the pest would need to eat 2 to 3 times that weight of prepared bait respectively for a 50% mortality rate.

The highest quantity that would need to be ingested for the largest rats would be around 200-300mg of bait depending on the formulation to eliminate 50% of the rats. If we double it for greater mortality rates, we’re looking at 400-600mg, or 0.4-0.6g, which is not much to eat at all, when we consider that a teaspoon of water weighs close to 5.0g, or ten times as much.

For more information on rat and mouse control, see the following articles:

More articles on Garden Pests, Diseases and Problems


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