Why do cats leave kidneys?

Table of Contents

When a cat catches prey, it wastes no time in feasting on it. However, from observations made by cat owners there is certain peculiar behaviour that raises questions when the cat eats a mouse. For example, a cat may end up leaving some of the vital organs behind such as what we see as ‘kidneys’. In this article, you will learn about the reason for this behavior. 

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Do Cats eat the Whole Mouse?

A cat may practically eat a whole mouse, but in some cases, they leave behind certain parts of the mouse’s body. The parts of a mouse that a cat refuses to eat varies from cat to cat, and it is usually due to the culture that was passed on to the cat by its mother. This also answers the question Why do cats leave kidneys?

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If you are wondering, What organ do cats leave behind? Based on observations, cats may leave the stomach, gall bladder, and tails behind. These organs are what look like ‘kidneys’ to us.  And the reason a cat may leave these parts behind is because these parts may cause the cat harm.  Even the tail can be a problem since it may be too much for the cat’s digestive system to cope with. 


Why do cats leave kidneys
Why do cats leave kidneys

Why do Cats Eat Their Prey?

There’s nothing quite as alarming as watching your beautiful feline shred apart a tiny mouse. It is horrible to see a cat yank off the body parts while the mouse is struggling to breathe.  Cats do not kill before they eat; they eat while the prey is still alive. Cats are natural-born predators, so there’s no way to stop them from expressing these natural traits. 

Cats are carnivores that catch and eat other animals. In terms of body size, mice are the best prey for cats to catch. Small, dry, roaming mice are animals that stimulate the hunting instinct of cats. For stray cats and free-range cats, mice are one of their ideal prey. When cats are hungry, it is natural to regard a mouse as food, chase it, catch it, and eat it.

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Why do cats eat Mice Head First? 

It is common to see a cat start eating a mouse from the head before tearing up the rest of the parts of the body to feast on. This is because the head of mice, just like most other animals, contains the brain and eyes. These two parts of the mouse are very juicy and taste different from the other parts. Furthermore, the brain is rich in phosphorus and other chemical substances that will improve the health and mental state of the cat.

Humans love to keep pets. Our relationship with these creatures is usually symbiotic; for example, we keep dogs for security or companionship; we keep cats to get rid of mice, and so on. For over 6000 years, cats have been domesticated by our human ancestors, and they do a very good job when hunting mice and rats.

According to research, cats were domesticated from wild cat species; thus, deep inside every cat, there is the potential to be a good hunter like the bigger cats in the wild such as the lion, tiger, leopard, etc. Albeit, domestic cats only hunt smaller prey and nothing large such as deer. When you take a cat as a pet, you are responsible, not only for catering to its needs but for its comfort too. A good bed to sleep in, regular grooming (if it is a Persian, for example), toys, and everything else it needs. 

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Is Eating Mice Safe for cats?

It is natural for cats that mice are prey, but when they eat mice, every cat owner needs to pay close attention. The reason for this is that mice can carry various parasites and pathogens, and eating mice can cause cats to become ill and can even lead to food poisoning.

Cats that have food poisoning show symptoms of becoming less energetic and experience bouts of vomiting and diarrhea. Should you believe that your cat has ingested a mouse, immediately consult your veterinarian.

You should also be aware of rodenticide poisoning caused by a cat accidentally eating a mouse that has ingested the poison.

Eating mice can cause various illnesses in cats, but here are three diseases that you should be especially careful with. Two of these diseases can all infect humans through cats. 

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Toxoplasmosis is one of the diseases that cats can get infected with by eating mice. Toxoplasmosis is not only present in mice but also in several raw types of meat, and once a cat ingests the meat, it becomes infected and acts as a vector of the disease.

Toxoplasmosis can also be transmitted to humans through contact with infected cat excrement. 

It is thought that direct transmission from cats to humans is rare because the protozoans that cause the illness in cat stools become infectious after 24 to 72 hours. However, if the insects contained in the stool are left as they are, they will live for several months, so care must be taken when handling cat stools and managing the hygiene of your cat.

Many cats and humans heal spontaneously when infected with toxoplasmosis, but it is important to note that pregnant women are more at risk when they get infected. If a cat is infected with toxoplasmosis, and a person is first infected with toxoplasmosis in early pregnancy, it can lead to miscarriage and serious fetal damage. Cat owners who are pregnant or preparing to become pregnant must ensure they create an environment where their cats do not come into contact with mice and have the right knowledge of how to deal with cats excrement. 

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Another disease to watch out for is echinococcosis. It is a disease known to infect red foxes and dogs, but recently it has been found that it also infects cats. Echinococcosis infects cats after eating mice that are parasitized by echinococcosis. Humans are infected by eating Echinococcus and its eggs contained in cat excrement. If your cat has been infected, you can treat it with anthelmintic drugs, but once it infects a person, it parasitizes the whole body after an incubation period of 5 to 20 years, and if it is not treated, it will lead to death.

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Taenia taeniae

Taenia taeniae is a tapeworm that parasitizes the small intestine of cats and can reach 30-60 centimeters in length. When a mouse eats an egg contained in the stool of an infected cat, it hatches in the body of the mouse, and when a cat eats the mouse it infects other cats. The tapeworm digs deep into the wall of the small intestine, which can cause holes in the intestine.

Symptoms rarely appear when a cat becomes infected, but a cat may do such things as rub its buttocks on the ground.  This is due to the itching caused by these tapeworms that spill out of the cat’s anus.  Since these worms are alive, they move around as they are excreted, which causes the cat to itch.

Also, when many tapeworms parasitize a cat the cat may lose its appetite and energy levels may drop.  The cat may also develop symptoms such as vomiting, diarrhea, and abdominal pain. Treatment is administered using anthelmintic drugs.

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Precautions around infections in cats

  • After emptying and cleaning the cat litter box, wash your hands thoroughly.
  • Avoid excessive contact with the infected cat.
  • If you get scratched by the claws of an infected cat, wash and disinfect the area immediately. 
  • Talk to your veterinarian to get the right advice on how to use the anthelmintic drugs prescribed for these infections.

If you allow your cat to move freely in and out of the house, even if your cat eats a mouse, you may not even know about it. If you keep the cat indoors, the chances of it eating a mouse are low except when the mouse comes into the house. However, finding a mouse does not mean that all cats will eat it. 

The food your cat consumes is essential to its health, hence, you should be knowledgeable regarding the dos and don’ts of the correct diet for your cat.

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Harmful Food for Your Cat

Cats should not be made to eat what humans eat; neither should they be fed with dog food. There are specially prepared foods and delicacies for cats, rich in vitamins and proteins to meet their health needs. 

Here are some types of foods that cats should not be allowed to eat.

Liver: When it is cooked, and the cat eats small quantities of it once in a while, there is no danger. But if your cat eats it often, it can result in vitamin A poisoning. This is a serious condition that can affect your cat’s bones.

Milk and dairy products: Specially prepared milk for cats is available in pet stores. If you give a kitten the milk you consume, it won’t harm it, but the digestive system in adult cats cannot successfully process the same dairy. This can lead to diarrhea and other ailments in the cat. 

Bones: Bones are not recommended as cat food. They can cause choking and even perforation of the intestines. Also, the hardness of the bones can cause fractures in the cat’s teeth.

Raw fish: When cats eat raw fish, it can lead to stomach upsets. Raw fish contains a type of enzyme known as thiaminase, which can also cause neurological problems in cats.

Alcohol: Beer, wine and foods containing alcohol or concentrated alcohol. These are drinks that are harmful not only to human health but also to the health of cats. About 10 mls of whiskey is enough to put an adult cat into a coma.

Chocolate: It may seem strange, but not only dogs love to eat it, but cats also love chocolate. However, chocolate is a forbidden food for cats because it contains a toxic agent called theobromine, which can lead to heart rhythm disorders, tremors, seizures, and even death.

Pasta, soft candies, and some diet foods: Some of these foods are sweetened with Xylitol. This can lead to increased insulin levels or liver failure. Initial symptoms include vomiting, drowsiness, and loss of coordination.

The innate curiosity of cats makes them constantly explore. 

After all, it is never clear what they could find by wandering in open spaces or peeking into all the hiding places in the house. There are many foods and other items in the home and garden, including plants that can be poisonous to your cat. Some of them are well known as poisonous plants, but others may be completely harmless at first glance.

For example, your cat might like your breakfast or the medicine you are taking, but these substances – although not harmful to us – can be poisonous and life-threatening to cats.  

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Items in the House That are Harmful to a Cat

Maintaining safe conditions in your home and garden is primarily a matter of common sense.  It is good practice not to leave things open and to prevent your cat from accessing what could easily be considered as delicious food. The tips that follow can assist in keeping your cat safe.

Inside the Home

Whether your medicines are over the counter or prescription medicines,  they should be kept out of your cat’s reach, preferably in a closed cupboard. Common examples of drugs used by humans but potentially fatal to cats, even in small amounts; are painkillers, cold and flu medicines, vitamins and diet pills.

Do not allow your cat near where detergents are stored or used. Some of these items can only cause stomach upsets in your cat, but others can act as poisons and cause severe burns to the tongue, mouth, and stomach. In some cases, such preparations can be fatal.

Substances and objects commonly used in the household are poisonous to cats – even if they do not look poisonous. Some of them can be poisonous even in small amounts. It is unnecessary to keep your cat locked alone in a room, but it is good to monitor what objects and substances are located in the place where your cat frequently visits. 

Some dangerous items and substances that the cat may want to play with include:

  • Pennies 
  • Naphthalene
  • Essential oils
  • Wet wipes
  • Dishwashing detergents
  • Batteries 
  • Winter warmers or similar heat sources
  • Cigarettes
  • Ground coffee

It is also good practice to watch out for life-threatening substances around your home, keeping in mind that your cat may decide to play with them. These can be, for example, vapors from household products such as detergents, pesticides, paints, and varnishes, as well as anti-mold and fungicides found in air conditioners, vents, filters, and humidifiers.

Be especially careful when removing lead-based paint and clean debris as quickly and thoroughly as possible. Some other lead-containing items that your cat may notice are lead-based paints, linoleum and resinous compounds.

Watch for signs of illness if your cat may have been in contact with any of these substances. Symptoms of poisoning in cats and signs of ingestion of such substances include vomiting, diarrhea or constipation, loss of appetite, uncoordinated movements, blindness, and seizures. It is always a good idea to consult a veterinarian if you are unsure of the symptoms.

Around the Home

Your cat loves to play in the jungle (which for you is just the garden of the house), but you should never allow your cat in it before the areas are completely dry after you have treated with fertilizers, herbicides, or insecticides. 

If in doubt, you can consult the manufacturer of the relevant products, who should inform you if they are safe for pets. Always keep such products in a safe place, because they can be poisonous to cats.

If you use baits and poisons for mice and rats, baits for ants and cockroaches, or those for snails and slugs, place them out of the reach of cats. You probably wouldn’t want your cat trapping its paw in one of them or eating something that’s trapped. Store in inaccessible places along with consumables for cars such as gasoline, oil, and antifreeze. Even the tiniest amount of antifreeze (containing ethylene glycol) can be fatal to cats.

There may also be some plants in your garden that are not suitable for your cat. 

Consult our list to check how safe the plants in your garden are for your cat.

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Plants that are potentially dangerous to cats

Some houseplants that tempt your cat can be dangerous to your cat’s health, as can certain plants that usually grow in the garden. Watch your cat carefully if you have such plants, and if you consider them an immediate danger, it is better to uproot them. 

These plants include Aloe vera, Apples (seeds), Apricot (stone), Autumn crocuses, Cherries, Yellow daffodil, Easter lily, Elephant ears, English ivy, poison ivy, Thimble, Geranium, Narcissus, Oleander, Oriental lily, Peach, Tomatoes and onions.


Cats are natural hunters, and thus, they prey on smaller animals. Due to their hunting instincts, they may choose to hunt for fun or feast. Usually, some well-fed cats won’t eat mice when they catch them and may leave one as a souvenir for their owner. The parts of the prey that cats do not eat may vary from one cat to another, and it is usually based on what the cat saw its mother do. Some cats will eat a rat kidney, while others will leave it alone. 


Hazel Buckley
Hazel Buckley

About Hazel Buckley
Hazel is an animal enthusiast and educator who grew up on a farm which her parents owned in Ingogo, KwaZulu-Natal, South Africa.  The farm was situated right under the Majuba Mountains - the site where the Anglo-Boer War was fought. 

Disclaimer: Whilst every effort has been made to ensure that the information published on this website is accurate, the author and owners of this website take no responsibility  for any loss or damage suffered as a result of relience upon the information contained therein.  Furthermore the bulk of the information is derived from information in 2018 and use therefore is at your on risk. In addition you should consult professional advice if required.