Introduction
Cats are obligate carnivores that regularly hunt and eat rodents like mice. However, they do not consume every part of their prey.
While cats are adept hunters and will readily catch and kill mice, they are surprisingly selective about which parts of the mouse they actually eat. There are a few key parts of mice that cats tend to avoid or leave behind.
Understanding why cats do not eat certain mouse body parts can provide interesting insights into feline behavior and instincts.
Skeleton
Cats typically avoid eating the bones and skeleton of mice. Their digestive systems are not designed to break down bone. According to Quora, cats don’t eat the bones of mice because “bones can cause complications as they pass through the digestive tract” (source). The Pet Forums also note that while cats are capable of eating bones, their bodies are not optimized for digesting them.
A cat’s teeth are adapted for gripping, tearing flesh, and chewing meat, not crunching bones. Their digestive tracts produce only low levels of the enzyme collagenase which is required to dissolve collagen, the protein that gives bone its structure and strength. Eating the bones could cause obstructions or damage the intestinal lining as they pass through.
So while cats are drawn to the tasty marrow inside bones, they tend to avoid consuming the actual skeletal structure of mice and other prey. Their bodies are designed to extract maximum nutrition from the soft tissues of their catch – the meat, organs and blood – while leaving behind the firmer, bonier parts.
Teeth
When cats hunt and kill mice, they often do not eat the mouse’s teeth. A mouse’s teeth are very small, making them difficult and not worth the effort for a cat to extract when eating its prey. Cats have no use for digesting the tiny teeth of a mouse, so this part is usually discarded or swallowed whole if the cat consumes the entire rodent (Veterinary Emergency Group).
A mouse’s incisors and molars are too diminutive for a cat to bother removing when feeding. Additionally, the mouse’s jaw structure attaches the teeth too securely for easy removal. It takes extra time and effort a cat rarely expends to detach the minute teeth. So a mouse’s dentition often stays intact even as cats devour the rest of the rodent’s body.
In summary, the minuscule size and firmly affixed placement of a mouse’s teeth within its jaws makes these body parts inconvenient and unrewarding for cats to remove during predation. Therefore, a mouse’s teeth are frequently left uneaten or disposed of when cats feed on mice.
Fur/Skin
While cats may nibble on fur or skin, they generally prefer eating the muscle meat of mice. The fur and skin has little nutritional value for cats. Cats evolved as carnivores to get the most calories and nutrients from prey animals like mice and rats by focusing on the protein-rich muscle meat.
According to the Animal Humane Society, the fur and skin contain little nutritional value for cats: “The most nutritious parts of the mouse for a cat to consume are the muscle meats.” The high collagen content in skin and fur may even be difficult for a cat to digest properly.
Cats have no nutritional requirement for the keratin found in fur. Their own bodies produce keratin for hair, nails, etc. Eating the fur provides no benefit. The society explains that cats prefer “meat, bones, and organs — skip the skin and fur.” The skin may just get chewed or tasted briefly during the hunting process.
Overall, while cats may nibble on the fur and skin of mice during play or hunting, they instinctively know that the calories and protein lie in the muscle meat. The indigestible fur and skin contain little of nutritional value, so cats focused on survival quickly eat the nutritious parts.
Organs
Cats tend to avoid eating the organs of mice, like the heart, lungs, kidneys and liver, as they find them unpalatable. According to sources[1], when cats hunt prey like mice, they typically avoid consuming the internal organs. The digestive organs in particular, like the stomach and intestines, are often left uneaten.
One reason proposed for why cats do not eat mouse organs is that they find the taste and texture unpleasant. The liver in particular has a strong flavor that cats may reject[2]. The organs also have a soft, mushy texture that does not appeal to cats.
Another reason is that organs like the stomach and intestines contain partially digested food and waste products that could make a cat sick. Cats seem to instinctively avoid these parts, even though mice themselves have no issue consuming the organs of their prey.
While cats may occasionally take an exploratory bite of organs like the heart, they usually end up leaving them behind. For cats, the muscle meat of mice is the tastiest and most appealing part of their prey.
[1]: https://www.quora.com/What-parts-of-a-mouse-does-a-cat-not-eat
[2]: https://biology.stackexchange.com/questions/19258/which-organs-do-cats-not-eat-on-their-prey
Extremities
A cat is unlikely to eat the paws, tails or other extremities of mice, instead focusing on the muscle meat. These parts have little meat. According to https://www.quora.com/When-cats-eat-mice-why-are-the-tails-not-consumed-and-often-left-behind-Is-it-because-they-are-already-full-by-the-time-they-come-to-the-tail-or-does-the-tail-lack-taste-and-nutritional-appeal, the tail may not provide as much nutritional value compared to other parts of the mouse, such as the organs and muscle tissue.
Intestines
Cats tend to avoid eating the intestines and stomach contents of mice they catch.1 The intestines and stomach have little nutritional value for cats and can potentially cause illness if ingested.2 Specifically, the stomach contains undigested food and bacteria that could upset a cat’s digestive system.3 While a cat may swallow small amounts of stomach contents when eating a mouse, they tend to avoid consuming the main portions of the digestive tract.
In contrast, other parts of a mouse like the muscle meat, liver, and heart are rich sources of protein and fat for cats. This explains why cats meticulously skin and debone mice, while often discarding the intestines and stomach.
Brain
The brain of a mouse has a mushy texture cats tend to dislike. So they often leave the head uneaten. According to one source, “They go for the brain because it is like fried chicken for us. It has a lot of fat” (Why do cats only eat the head of a mouse?). While the brain is high in nutrients, the texture can be unappealing to cats. That’s why cats sometimes leave the head and brain uneaten after killing and partially eating a mouse.
Eyes
A cat will typically avoid eating the eyes of mice and other rodents they catch. The eyes have a jelly-like consistency if punctured that cats find unappealing. Cats have a strong sense of smell and taste and the texture of mouse eyes is unpalatable. According to https://www.ucl.ac.uk/culture-online/case-studies/2022/mar/do-cats-actually-eat-mice-or-do-they-just-see-them-toy, cats have a natural instinct to avoid the eyes during feeding due to their gelatinous interior. The solid outer layer disguises the inner texture, but once punctured the jelly-like consistency is exposed. This triggers the cat’s innate preference to not consume the eyes.
Conclusion
In summary, cats are selective about which parts of a mouse they consume, preferring the muscle meat over bones, organs, extremities, and other unpalatable parts. While mice provide cats with a nutritious and protein-packed meal, cats tend to avoid eating certain parts that are difficult to digest, unappetizing, or potentially harmful if consumed. Cats typically eat the fleshy parts of a mouse like the abdomen and thighs, while leaving behind indigestible bones, as well as the head, tail, feet, brain, and most internal organs. Their selective eating behavior maximizes the nutritional value they obtain from prey while avoiding toxins or obstructions that could come from consuming a mouse whole. So in the end, cats are not indiscriminate mouse eaters, but rather strategic carnivores that know which mouse morsels make for the tastiest, safest, and most beneficial meal.
