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.
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 won’t eat baking soda on its own, we need to mix it with other ingredients that are appealing to them. Here are three easy recipes which work really well.
Chocolate Cake Mix and Baking Soda Rat Mouse Bait
Rats and mice love chocolate and that includes chocolate cake, but there’s no need to bake them a cake! Just mix equal parts of chocolate cake mix and baking soda and they’ll be just as happy to eat that too.
Ingredients required:
- Chocolate cake mix or chocolate brownie mix
- Baking soda
Materials required:
- Disposable shallow bowl – can be made by cutting the bottom section from a plastic soft drink bottle, milk carton or yoghurt container or can use a deep plastic jar lid.
To make this chocolate cake mix rodent bait:
- Pour equal parts chocolate cake mix and baking soda into a shallow container and mix it well. A few heaped teaspoons of each will make enough bait.
- The mix can be used dry if a source of water is provided, just fill another similar shallow bowl with water. This is necessary as rats and mice need to drink water if their food is dry.
To use the mix in a form that’s wet, add a small amount of water at a time, not all at once, and mix well, and keep adding more water until it turns into a thick paste. - Place the shallow bowl with the bait along walls or between spaces where rats frequent. Leave the bait in the same location for a few days, as rats are shy and may inspect the bait but not eat it until it feels safe to do so.
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:
- Peanut butter
- Baking soda
Materials required:
- Small disposable saucers made from a plastic jar lid, or by cutting down a plastic bottle or milk carton
To make this peanut butter rodent bait:
- 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.
- Spoon two or more heaped teaspoons of the bait mixture onto each small disposable saucer.
- Place the saucers with the bait along walls or between spaces where rats frequent. Leave the bait in the same location for a few days, as rats are shy and may inspect the bait but not eat it until it feels safe for them to do so.
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:
- Flour (any kind)
- Sugar (regular white sugar or finely powdered castor sugar)
- Baking soda
- Chocolate powder or sprinkles (optional but highly recommended)
Materials required:
- Small disposable saucers made from a plastic jar lid, or by cutting down a plastic bottle or milk carton
To make this flour, sugar and chocolate rodent bait:
- 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!
- 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.
- Spoon two or more heaped teaspoons of the bait mixture onto each small disposable saucer.
- Place the saucers with the bait along walls or between spaces where rats frequent. Leave the bait in the same location for a few days, as rats are shy and may inspect the bait but not eat it until it feels safe for them to do so.
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 Can’t Burp or Vomit!
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 to Eliminate Them?
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:
- Sodium bicarbonate LD50 Rat (oral) is 4,220 mg/kg
- Sodium bicarbonate LD50 Mouse (oral) is 3360 mg/kg
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.
How Quickly Does Baking Soda Rat Bait Work?
When dispatching pests, it’s important to do it humanely, so many people ask how quickly a rat bait that uses baking soda (also known as bicarbonate of soda or sodium bicarbonate) works.
After a fair bit of research, all I could find was a video from the US where a rat caught in a live-catch cage trap was given a dry baking soda bait mix and a saucer of water. It was inspected 20 hours later, where it was found to be deceased. This only tells us that it takes less than a day to work but doesn’t provide any more accurate information than that.
Since the chemical reaction of sodium bicarbonate with the rodent stomach acid is very quick, I suspect it is a reasonably rapid process. To test this, drop a half a teaspoon of baking soda into a glass with a centimetre or two of vinegar in it to see fast it fizzes up, froths and expands. Do it in the kitchen sink to avoid a mess!
From my biomedical science background, speculating on the exact mechanism of action, the swelling of the stomach, which happen fairly quickly, would likely press down hard on the diaphragm muscles which control breathing, quickly causing suffocation of the rodent. There are lots of internet claims that baking soda bait kills rodents by rupturing their stomach, but I have doubts that would be the case, and without carrying out an autopsy of the rodents, that claim would be hard to verify. It’s quite an unpleasant subject to consider, which should explain why nobody has tested this by timing the demise of rodents after eating the bait.
Using baking soda rat and mouse bait is far more humane than commercial poison rat baits, which take a week or two to work through slow internal hemorrhage, which is a very prolonged and gruesome way to dispatch them. With baking soda baits, there is also no risk to other wildlife or pets being poisoned if they eat the dead rodents.
For more information on rat and mouse control, see the following articles:
- How To Tell If You Have Rats and Mice in Your Home or Garden
- The Best Ways to Trap Rats and Mice That Really Work
More articles on Garden Pests, Diseases and Problems
References
- Government of Western Australia, Department of Health, “Protect your health – keep rats and mice under control”, https://www.healthywa.wa.gov.au/Articles/N_R/Protect-your-health-keep-rats-under-control
- Horn, Charles & Kimball, Bruce & Wang, Hong & Kaus, James & Dienel, Samuel & Nagy, Allysa & Gathright, Gordon & Yates, Bill & Andrews, Paul. (2013). Why Can’t Rodents Vomit? A Comparative Behavioral, Anatomical, and Physiological Study. PLoS One. 8. e60537. 10.1371/journal.pone.0060537.
- Smithsonian Magazine, Smart News, “Why Rodents Can’t Throw Up, In Case You Were Wondering”, https://www.smithsonianmag.com/smart-news/why-rodents-cant-throw-up-in-case-you-were-wondering-25707720/
- National Center for Biotechnology Information (2022). PubChem Compound Summary for CID 516892, Sodium bicarbonate. Retrieved May 16, 2022 from https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-bicarbonate.
- Lewis, R.J. Sr. (ed) Sax’s Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 3233
The flour, sugar and chocolate recipe picture has flour, sugar and baking soda which confused me a bit.
Hi Jennifer, I didn’t want to make the headings too long for all of these baking soda recipes, and left the words ‘baking soda’ out because its the common ingredient to both recipes and the topic of the article. In case the recipe headings are a bit confusing, they’ve been updated to include the baking soda part too! Thanks for letting me know! 🙂
The point was that the flour, sugar and chocolate sprinkles recipe doesn’t have any baking soda listed in the ingredients, so instead of a picture of baking soda, a picture of chocolate sprinkles would make more sense. Or just leave out the baking soda picture. (and amend the title back to what it was before)
Apologies Jennifer, thanks for pointing that out, that’s fixed now, as all recipes listed are baking soda recipes!
Very interesting thank you, but isn’t this more cruel way for them to die than plain old traps? I also worry about where they will die.
Hi Linda, thanks for your question. I value all living things, and pest rodents are intelligent animals, they’re just like pet rats and mice that people keep, but they’re wild and carry lots of diseases and parasites, so it’s unfortunate that they have to be exterminated. The baking soda bait works faster than conventional poison baits, but nothing is faster than a quality trap that is strong enough to work almost instantly. Traps need to be used in a safe way to avoid harming non-target wildlife, and there are optimum ways to use them for maximum effectiveness. I’ll be writing an article soon on the safest and most effective ways to use rat and mouse traps, based on some research and a lot of experience! There are also live-catch traps, which don’t harm the animals, so they can be relocated. Having a choice of options allows us to select the most viable and humane approach for our circumstances.
Thank you, I look forward to more articles. So far have not got any issues with rodents in the house I moved into a few months ago, but like to be prepared just in case!
How quick is quick i.e. how long does the baking soda take to kill a single rat?
How does it work, do they explode after eating the baking soda as it turns into gas in their stomachs?
I have visions of smearing/dolloping peanut butter + baking soda mix on top of my clourbond super sixty six metal fence, resulting in exploded rat guts & blood all down the fence?
The rats in my garden area a severe problem the orange tree attracts them ;(
Hello Angelo, are you able to answer my questions in my above post dated September 16th??? If you could I would be most grateful.
BTW have you actually used & tested the recipe yourself, & witnessed the results???
Read the article. All of it. Properly.
I am assuming this would work for squirrels. Would the same recipe be effective for them? What concentration of baking soda be optimal for them?
Squirrels have been drastically increasing in numbers and I need a effective way to control them.
Great question! Honestly, it’s hard to tell if it will work on squirrels. Despite lots of websites citing the study I referenced, “Horn, Charles & Kimball, et al (2013). Why Can’t Rodents Vomit? A Comparative Behavioral, Anatomical, and Physiological Study“, and concluding that ALL rodents can’t burp, that may not be the case. From my background in science, looking at the results of the research, what we can say that only all the rodent species tested (see image below) could not vomit
Looking at the actual study, from the squirrel-related rodents, which includes the Aplodontidae (mountain beaver) family, Sciuridae (squirrel) family and Myoxidae (dormouse) family, only mountain beavers were tested. Curiously, these critters are not beavers, don’t live in mountains, and look nothing like squirrels.
While it may be tempting to infer from the sample of rodent species tested that squirrels will be the same, without actual objective evidence, it’s not scientific to make that claim, as there may be exceptions due to the differences in the anatomy of the digestive systems between different rodents. No actual squirrels were tested. Until someone can show evidence that a bicarbonate of soda bait has worked on squirrels, the most scientific thing to say here is that we’re not really sure!
Use a .22 LR rifle and eat the squirrels. They are delicious.
Could you use washing soda that has a higher Ph? What about using Apple cider vinegar in the water?
Hi Mark, washing soda, which is sodium carbonate (Na₂CO₃), while baking soda or bicarbonate of soda, is sodium bicarbonate NaHCO₃. There are two reasons why we don’t use washing soda for this purpose:
Reason 1 – bicarbonate of soda is preferred to washing soda is that the same amount produces more carbon dioxide gas than washing soda, and I’ve explained the chemistry below for anyone who is interested.
Looking at some basic chemistry:
The molecular weight of sodium carbonate (Na₂CO₃) is approximately 105.99 g/mol (grams per mole)
the molecular weight of sodium bicarbonate (NaHCO₃) is approximately 84.01 g/mol (grams per mole)
In chemistry, one mole of a substance is defined as an amount of that substance that contains approximately 6.02214076 x 10^23 particles. This number is known as Avogadro’s number and is a unit of measurement that allows chemists to count a very large number atoms or molecules in a practical and manageable way.
The molecular weight tells us that 6.02214076 x 10^23 molecules of sodium carbonate will weigh 105.99 g, while that same number of sodium bicarbonate molecules will weigh much less at 84.01 g. Looking at the chemical formulas for each sodium carbonate (Na₂CO₃) and sodium bicarbonate (NaHCO₃), we can see that they both have one carbonate ion (CO₃-) which will produce one carbon dioxide (CO₂).
Now, to calculate how much carbon dioxide (CO2) will be produced when 1 gram of each substance reacts with an acid, we need to consider the chemical reactions involved.
Sodium Carbonate (Na2CO3):
When sodium carbonate reacts with an acid (e.g., hydrochloric acid, HCl in the stomach), the following reaction occurs:
Na2CO3 + 2HCl -> 2NaCl + H2O + CO2
From the balanced chemical equation, you can see that 1 mole of sodium carbonate (105.99 g) produces 1 mole of CO2. So, 1 gram of sodium carbonate will produce 1/105.99 or 0.0094 moles of CO2.
Sodium Bicarbonate (NaHCO3):
When sodium bicarbonate reacts with an acid (e.g., hydrochloric acid, HCl in the stomach), the following reaction occurs:
NaHCO3 + HCl -> NaCl + H2O + CO2
From the balanced chemical equation, you can see that 1 mole of sodium bicarbonate (84.01 g) produces 1 mole of CO2. So, 1 gram of sodium bicarbonate will produce 1/84.01 or 0.0119 moles of CO2.
The actual amount of CO2 produced in grams, we can multiply the molar mass of CO2 (approximately 44.01 g/mol) by the moles of CO2.
1 gram of sodium carbonate (Na₂CO₃) when reacting with an acid will produce 44.04 g/mol x 0.0094 moles of CO2 = 0.42g of CO2
1 gram of sodium bicarbonate (NaHCO₃) when reacting with an acid will produce 44.04 g/mol x 0.0119 moles of CO2 = 0.52g of CO2, or 24% more CO2
Reason 2 – bicarbonate of soda is both palatable and edible, while sodium carbonate is not, and animals will avoid it.
Sodium carbonate is strongly alkaline, with a pH around 11-12.
Sodium bicarbonate, by comparison, is slightly alkaline and has a pH around 8.3-8.4, which is closer to neutral pH of 7.0 compared to sodium carbonate.
Animals can detect the taste of alkaline foods to avoid them because of the toxicity of high pH and choose neutral foods instead. This was demonstrated in studies using fruit flies, which enabled scientists to identify a previously unknown chloride ion channel, which they named alkaliphile (Alka), as a taste receptor for alkaline pH.
In fruit flies lacking the taste receptor for alkaline pH, they lost their ability to discriminate against alkaline food when presented with it, and after fruit eating food with high pH, their lifespans were shortened. If the pH of a food is too high it can be harmful to animals causing health concerns such as muscle spasms, nausea, and numbness, so animals have evolved the capacity to avoid such foods.
Reference: Monell Chemical Senses Center. “Molecular basis for alkaline taste.” ScienceDaily. ScienceDaily, 20 March 2023..