Introduction
Carnivores are animals that eat primarily meat, while omnivores eat both plant and animal material. House cats (Felis catus) have long been considered obligate carnivores, meaning they require certain nutrients found only in animal flesh to survive. However, the true extent to which domestic cats rely on meat remains a topic of debate among researchers. On one hand, cats are descendants of desert-dwelling wildcats that subsisted on small prey and had little access to edible plants. On the other hand, many house cats seem able and even eager to ingest small amounts of cat-safe fruits, vegetables, and grains. This article explores the evidence regarding cats’ status as carnivores versus omnivores through an analysis of their anatomy, natural diet, nutrient requirements, and feeding behavior.
Anatomical Evidence
Cats have several anatomical features that suggest they are optimized for eating meat. First, their teeth are adapted for catching, killing, and tearing animal prey. They have long, pointed canine teeth to seize prey as well as sharp incisors and carnassial teeth to slice meat into smaller pieces (Purina, n.d.). Dogs and bears have similar dental structures since they are also carnivores or omnivores.
In addition, cats have a relatively short digestive tract compared to omnivores and herbivores. Their small intestines are only about 3-4 times the length of their body, whereas an herbivorous sheep’s intestines are 15-25 times its body length. The shorter intestine allows cats to rapidly digest and absorb nutrients from animal flesh before it putrefies. Plant matter takes much longer to break down, so a shorter tract is less adapted to a vegetarian diet (Chatham’s Small Animal Hospital, 2020).
Dietary Preferences
Studies have demonstrated that cats have a strong preference for meat over plant foods. Free-ranging and feral cats show a preference for consuming approximately 90-95% meat-based prey, such as small rodents. An analysis of dietary samples from free-roaming feral cats by Plantinga et al found that 95% of their diet was composed of moderate to high protein animal-based foods like rodents, birds, insects and eggs (Plantinga et al.). Cats require high protein intake, approximately 2-3 times more dietary protein than humans. Their bodies are adapted for deriving the majority of their energy and nutrients from protein and fat, rather than carbohydrates.
Ability to Digest Plants
Cats have a limited ability to digest and metabolize plant matter due to the structure of their gastrointestinal tract. According to a study by the National Center for Biotechnology Information, cats lack some key metabolic pathways that allow for the breakdown of plant material (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7143243/). Their stomachs also have a lower pH than dogs and humans, making it difficult to break down cellulose and extract nutrients from plants. While cats may chew on and ingest small amounts of grass or other plant matter, they lack the enzymes needed to properly digest it. Plant proteins especially tend to pass through their system undigested.
Essential Nutrient Requirements
Cats have an obligate carnivore nutritional profile, meaning they require high levels of certain nutrients found primarily in animal-based proteins. According to CatHarmony, cats cannot synthesize certain key nutrients themselves and must obtain them through their diet. The most critical of these is taurine, an amino acid essential for eye and heart health that is only found naturally in meat. Cats who do not get enough taurine can develop serious vision and cardiac issues. Other nutrients cats need at high levels include arginine, methionine, and vitamin A. Since these are not found in adequate amounts in plant sources, cats fed exclusively plant-based diets may develop deficiencies over time.
Commercial Cat Food
Most commercial cat foods are formulated to mimic the nutritional needs of obligate carnivores. According to The optimum meat ratio in cat food, cat food with a meat content of 80% or higher is recommended to meet a cat’s protein requirements. This means the majority of the food originates from animal sources, with only about 20% from plant materials.
As noted on Commercial Cat Foods – CatInfo.org, many experts suggest sticking with poultry, rabbit and other meats as the bulk of a cat’s diet. Most commercial dry foods contain around 90-95% meat, according to responses on What percentage/amount of meat is used for dog and cat …. This high meat content shows how cat foods are formulated to match the carnivorous requirements of felines.
Health Impacts of Plant-Based Diet
Feeding cats a plant-based diet can have multiple negative health impacts compared to a diet based on animal products. Cats are obligate carnivores, meaning their bodies are designed to obtain nutrients primarily from meat sources. Forcing them to follow a vegan or vegetarian diet increases their risk of developing serious nutritional deficiencies over time.
One of the biggest concerns is that plant-based diets do not provide enough high-quality protein for cats. Unlike dogs, cats have a higher protein requirement and cannot thrive on plant proteins alone. Taurine and arginine are two essential amino acids found naturally in animal products that cats cannot synthesize enough of on their own. Deficiencies in these amino acids will lead to heart, eye, and reproductive problems.
There is also a lack of vitamin A and B vitamins like vitamin B12 in vegan cat food. Vitamin A is critical for eye and immune health. B12 is needed for proper nerve function and red blood cell formation. Symptoms of B12 deficiency include weight loss, lethargy, and anemia. Supplementing these nutrients does not provide the same health benefits as obtaining them from meat sources.
In addition to deficiencies, there are concerns about carbohydrate sensitivities in cats. Vegetarian and vegan cat foods often have higher proportions of grains, legumes, fruits and vegetables. Cats tend to have a low tolerance for carbohydrates, increasing their risk for obesity and diabetes when fed a grain-heavy diet long-term. Unlike dogs, most cats have not evolved the ability to efficiently digest plant matter.
Finally, taste and texture are a major barrier when it comes to getting cats to accept plant-based foods. Cats generally prefer animal-based proteins and fats when given the choice. They often refuse foods made from plant ingredients, leading to malnutrition. Overall, carnivorous cats do best on meat-based diets they are designed to eat.
Sources:
https://thepets.net/cat-diet-nutrition/
Behavioral Evidence
Cats have strong hunting instincts and meat-seeking behaviors that provide evidence that they are obligate carnivores. Even domesticated house cats exhibit hunting behaviors, like stalking, pouncing, and playing with prey, indicating their evolutionary drive to seek animal protein (Crowley, 2019). Studies show over 30% of pet cats successfully catch prey, primarily small mammals and birds, at least once per month. This is likely an underestimate since owners do not always witness the hunting (Crowley, 2019).
Experts attribute this to cats being natural hunters that are still driven by instinct to exhibit hunting behaviors, despite not needing to hunt to survive with owners providing food. It is an innate predatory response when cats see movement or prey animals (Purina, 2021). Their play mimics hunting techniques they would use to catch prey in the wild. The hunting provides cats cognitive stimulation and allows them to act on natural instincts (Icatcare, 2019).
Overall, the persistent hunting behaviors of domestic cats, even when fed an adequate diet, demonstrate their evolutionary adaption as obligate carnivores dependent on animal protein.
Classification Among Zoologists
Zoologists classify cats as obligate carnivores, meaning they rely on nutrients found only in animal flesh for their dietary requirements (https://www.scientificamerican.com/article/veggie-cat-food/). Cats are similar to other carnivores like lions, tigers, and leopards in this way.
Obligate carnivores have a higher requirement for proteins and fats found in animal sources than omnivores or herbivores do. They also lack specific metabolic adaptations required to utilize plant sources efficiently. As a result, obligate carnivores like cats thrive best on a meat-based diet (https://vetmed.tamu.edu/news/pet-talk/cats-are-carnivores-so-they-should-eat-like-one/).
Conclusion
In summary, the evidence overwhelmingly shows that house cats are true carnivores optimized for a meat-based diet. Their anatomy, physiology, behavior, and nutritional requirements all point to obligate carnivory. Cats have sharp teeth and claws suited for hunting prey, require high levels of protein and fat from animal sources, and thrive best on meat-based commercial diets or raw food diets that mimic whole prey composition. While cats may nibble on grass or other plants, they lack the ability to properly digest and extract sufficient nutrition from plant matter alone. Attempting to sustain cats on a vegan or vegetarian diet would be extremely detrimental to their health and quality of life.
The optimal diet for cats is one high in quality animal proteins and fats. Commercial meat-based cat foods or balanced homemade raw diets are recommended to provide complete and balanced nutrition. Cats also require adequate hydration from wet food or additional water. Owners should provide proper enrichment through toys, scratching posts, and opportunities to exhibit natural hunting behaviors. With a species-appropriate carnivorous diet and proper care, cats can lead long, healthy, and enriched lives.
