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Why do big cats exist but not big dogs?

Dogs and cats are the two most popular domesticated animals. Many of us have one or both of them in our home. This can lead you to wonder, why aren’t there big dogs as there are big cats? When it comes to the domesticated versions of these animals, dogs are generally larger than cats. So why are wild cat species larger than wild canine species? 

Why do big cats exist but not big dogs?

There are a few reasons why no big dogs exist today. These include evolution, and a difference in hunting styles.

What Determines Size? 

Both cats and dogs are predators. Predators will evolve to kill nearly any prey in their environment, including large animals. They will grow as large as is necessary to bring down large prey.

Once they reach this size, there’s no reason for them to grow larger. Larger animals are less agile and require more calories than their smaller counterparts, so there’s no evolutionary advantage to becoming larger than needed. 

Specialization is also a factor. It benefits predators to be capable of taking down as many types of animals as possible. This gives them more hunting opportunities. 

An animal that is too large would be limited to hunting the very largest animals. For example, a lion can take down a zebra, but not an elephant. If it were large enough to kill an elephant, it would be limited to elephants as a prey source.

It would be too slow to take down smaller animals, because they would move faster. Small animals wouldn’t provide enough calories to be worth chasing for a huge animal either. 

Calories in vs. calories out is a big consideration for predators in the wild. Each hunt burns calories. The predator must be able to get more calories than they burn during the hunt from the prey. The larger the animal, the more calories it burns. So an extremely large animal would need large prey to consume enough calories. 

Hunting Style

Dogs and cats are different types of hunters, and occupy different roles. Cats are typically solitary hunters. This means they need to be large and muscular enough to take down large prey on their own.

Dogs, on the other hand, hunt in packs. They don’t need to be as large as their prey, because several dogs will attack the prey at the same time. 

The way they chase and kill prey is also different. Cats sprint and pounce, bringing their prey down with sheer force and power. They typically make one attack, and either bring the animal down, or it escapes. 

Dogs, however, will wear their prey down. They will nip, bite, and chase until the prey is exhausted and injured enough to take down. 

Because a cat uses power to overcome it’s prey, it has to be heavy and well muscled. Dogs are built for endurance, so they need to be lighter. 


The claws also play a role in the size of cats and dogs. If you’ve ever had a scratch from a house cat, you are aware that they can be sharp. Cats have retractable claws. This helps them stay sharp, and prevents the cat from accidentally injuring itself or another cat.

Dog’s claws don’t retract. They are in constant contact with the ground, which essentially keeps them filed down. 

 Big cats have razor sharp claws. These claws can be used to hook prey so it can’t escape. They can also be used to disembowel prey or cut its throat. 

Dogs don’t have sharp claws. Their claws are not used as a weapon the way cats’ claws are. Instead, dogs use their teeth and jaws as their weapons. Cats need strong muscular arms to power their claws. Dogs don’t use their claws in this manner, so their limbs don’t need to be as muscular. 

Epicyon Haydeni 

You may have heard of the prehistoric Dire Wolf, which would tower over today’s wolves. However, you probably haven’t heard of Epicyon haydeni. This prehistoric animal was actually bigger than  the Dire Wolf. In fact, it was the size of today’s African Lions. The largest of this species was as big as a grizzly bear. It was the largest dog-like animal that is known to exist. 

Approximately 40 million years ago, there was the family Canidea. The Canidea family had three dog-like species. These were Hesperocyoninae, Borophaginae and Caninae. Today’s dogs come from Caninae. 

Over time, Borophaginae and Hesperocyoninae began to grow larger, while the caninae family stayed the same size. This put the two species in competition for each other for larger prey. Borophaginae was a better, more efficient hunter. The other species died out, because they couldn’t compete with Borophaginae. 

Then, there was Borophaginae and the smaller caninae. Each of these species had its niche. Borophaginae hunted large animals, and caninae hunted small and medium sized animals. The Epicyon haydeni evolved from the Borophaginae. It was so large, it could only hunt the largest prey. This specialization eventually led to its downfall. 

The Epicyon evolved when there were no cats on the Americas. They killed the large prey, and there was no competition for these large animals after the Hesperocyoninae died out, until the cats arrived. 

The big cats were better hunters than the Epicyon, so they eventually out hunted them. The caninae was the only line of canidea left, and they were the smallest branch. This is where today’s wolves, dogs, and coyotes came from. 

Giant Animals and Humans

There were many gigantic animals before humans came on the scene. Megafauna, including the Giant Ground Sloth, the Giant Wombat, and the Hornless Rhino, which was 10 times larger than the modern day variety.

 These animals started disappearing 125,000 years ago. Animals that survived humanity’s appearance are 100 to 1,000 times smaller than those that disappeared. 

In fact, the trend started with the appearance of Homo Erectus, nearly 2 million years ago. Once humans switched from a mostly plant-based diet to hunting meat, the largest mammals were hunted. As early humans spread across the world, the average mass of the animals was halved. 

When they arrived in the America’s the impact was drastic. 15,000 years ago, the average weight of a mammal had dropped from 216 pounds to 17 pounds. 

Do dogs and cats have a common ancestor?

Cats and dogs are both in the Carnivora order, but their last common ancestor lived about 42 million years ago. They share the Carnivora order with other mammals, including bears, skunks, walruses, and seals. Contrary to the name, not all animals in the Carnivora order are carnivores, and not all mammals are included in the order. 

Today’s cats and dogs share the same ancestor, Dormaalocyon latouri. This tree-dwelling mammal was small, and ate smaller mammals and insects. This species is 55-42 million years old.

However, the earliest shared ancestor is the Miacidae family. The Carnivora order diverged from the Miacidae order approximately 42 million years ago. Viverravidae is thought to be the first Carnivoran, which existed as early as 60 million years ago. However, there’s scientific debate as to whether Viverravidae belongs to the carnivoran order. 

Do dogs and cats share a lot of DNA?

Dogs and cats do share some DNA, due to their common ancestor. Surpisingly, humans are more closely related to cats than dogs. We share 90% of our DNA with cats, and only 84% of DNA with dogs. 

Even more surprising, we share nearly 90% of our DNA with mice. This is one reason why mice are used for experiments. 

Are dogs big cats?

No, dogs and big cats are very different species. They are both from the order Carnivora. From there, they are divided into feliforms and caniforms. 

Feliforms include cats, hyenas, and mongooses. Caniforms include dogs, raccoons, bears and walruses. It’s essentially a large family tree. All cats and dogs share a common ancestor along with other members of the carnivora order.

Are Tigers considered dogs?

No, tigers are a member of the feliform group, not the caniform group. Tigers are clearly catlike. They have a carnivorous diet, retractable claws, and sharp cat teeth. In fact, they share 95% of their dna with the domestic cat.

There are a few surprises among the canidae family, however. Hyenas may appear to have a closer resemblance to dogs than to cats, but they are members of the feliform family. Bears, on the other hand, are a member of the Caniformia order, which makes them relatives of the dog. 

Do big cats act like dogs?

There can be some similarities between big cats and dogs. Of course, this depends on your definition of big cat as well. The term can describe large domestic cat breeds, or cats like lions and tigers. 

Domestic Large Breed Cats

Some domestic large breed cats have actually been bred to be more doglike. These are often called puppy cats, and they resemble dogs in more than just size. 

Cats have a reputation for being aloof. They don’t want constant attention from their owners. They do things on their terms, and they lack a dog’s desire to please.

However, some breeds of cat possess traits we often associate with dogs instead of other felines. These cats are known to follow their owners around and seek lots of affection. 

Cats are usually territorial, but puppy cats often enjoy interacting with other felines. They can also be walked with a leash and collar, and enjoy baths as dogs do. 

Canine Species vs Large Cats 

There are some behaviors cats of all sizes have in common with dogs. Both species mark their territory with urine. Cats also use their face to mark, while dogs have scent pads in their paws. 

Both cats and dogs enjoy playing. This includes wild and domesticated species. Young canines and felines play to learn how to hunt. Domesticated cats and dogs continue to play because they don’t hunt. Mature wild cats and dogs will spend their energy hunting. 

Both species use vocalizations to communicate as well. Dogs bark, yip, or howl. Cats meow or roar. They both have a keen sense of smell as well. 

Some big cats are social. Lions live in prides with other lions. Tigers will sometimes socialize with each other, but they are solitary hunters. Not all canines are pack animals. Coyotes tend to be solitary. 

When it comes to hunting style, lions closely resemble wolves or wild dogs. They work together to take down prey, and will often wear the prey down as dogs do. 

Other cats are ambush predators. They will wait for the opportune moment to pounce on their prey, just like your cat will pounce on a toy. 

Hyenas are the closest to dogs in terms of behavior and appearance. Their vocalizations are even similar to dogs, and very unsimilar to the roar of a lion or tiger.