Buzz
Both top carnivores in nature, why are dogs significantly smaller than cats? The largest cat, the Siberian tiger, weighs an average of 200 kg and can reach up to 300 kg. The largest existing dog species is the Northwestern wolf, with an average weight ranging from 40 - 50 kg and a maximum of over 70 kg. Why is that so?
The feline family are ambush predators, excelling in silently approaching prey and then using their strength to subdue them. During hunts, they rely on camouflage and individual strength, thus larger body size offers an advantage in prey subjugation.
On the contrary, dogs are pursuit predators, unable to deliver a single killing blow like cats. Instead, they often bite relentlessly at the flanks and legs of their prey to induce bleeding, shock, and exhaustion. Hence, for dog species, speed, endurance, and teamwork are crucial. Overly large size would impact their ability for sustained long-distance hunting.
Thus, we observe that larger felines like lions, tigers, and leopards can swiftly overpower larger prey. Large wild dogs such as wolves and African wild dogs, despite their significantly smaller size, can also bring down large prey through collective strength and long-distance running advantage. Their body structures are highly adapted to their respective lifestyles, representing optimized evolutionary solutions.
But who dictates that cats can only ambush and fangs can only chase? In the extensive evolutionary history of fangs, has there never been a colossal ambush predator like the big cats?
Throughout history, the canine family has been divided into three subfamilies: Borophagus, Hesperocyon, and True Canine. These subfamilies continuously competed to become the top predators in the food chain. However, none of them succeeded in evolving into super predators like those in the feline family.
Dogs first appeared with the Hesperocyon subfamily. The initial members of this subfamily lived in the Western United States 40 million years ago, at the end of the Eocene epoch. They were very small, weighing only 1-2 kg, and primarily preyed on small rodents such as rabbits and mice. Based on fossil distribution, we know they lived in groups, or packs, from this early stage.
It's evident that the canine family lived in groups from the early stages of evolution, relying on pack strength to limit individual development.
Since then, they followed this evolutionary path, growing larger and stronger. Around 21 million years ago, the Austrian dog species, weighing about 20 kg, evolved. This marked the first appearance of such a large dog species in evolutionary history, eventually differentiating into wolf and wild dog breeds.
Comparatively, at the same point in time, the common ancestor of the feline species still roamed the dense forests of Europe. In terms of development, the canine family had a head start over the feline family.
The first subfamily of dogs was supposed to continue evolving and growing stronger. However, they suddenly disappeared 15 million years ago, abruptly ending the initial large-scale formation process. What happened? This directly relates to the second subfamily we'll discuss next.
The second subfamily of the canine family is Borophagus. It can be said that this subfamily is the most successful evolutionary branch in the history of the canine family. They were the largest and most diverse. However, during this period, they were surpassed by the feline family.
This second subfamily first appeared in the early Oligocene 32 million years ago. As the first subfamily had established an advantage by then, to avoid direct competition with their predecessors, the initial members of the second subfamily were all small omnivores weighing a few kilograms, some even less than one kilogram, resembling modern-day bears.
Subsequently, the second subfamily evolved to be larger and more carnivorous, challenging the dominance of the first subfamily. In this escalating arms race, the first subfamily became the losers. In the Miocene epoch 16 million years ago, the second subfamily evolved into species weighing 20-40 kg, completely replacing the first subfamily.
With the extinction of the first subfamily, the second subfamily entered its golden age. At that time, there were 30 dog species living in North America, compared to only 9 dog species in present-day North America.
Starting from 17 million years ago, the feline family began to invade the territory of dogs - North America. Meanwhile, climate change caused a sharp drop in temperature, and forests gradually turned into grasslands. In the changing environment, the canine family and the feline family began fierce competition, leading to the decline and extinction of the second subfamily of the canine family.
In open environments, accessing prey became more difficult, and at this point, the environment favored ambush predators more than ever. Cats are professional ambush predators, with stronger bodies, larger and stronger necks, and sharper claws than dogs. They can quietly approach prey, target vulnerable points, and finish them off quickly.
Under the pressure of cats, the second subfamily of the canine family began to evolve towards bone-eating and carrion, as there were no hyenas in North America, and the niche of bone-eating animals was largely vacant. This evolutionary strategy eventually brought glory to the second subfamily, evolving into the largest dogs in history - Epicyon. Among them, the body size of the Epicyon haydeni genus could exceed 100 kg. However, their competitors at this time were saber-toothed tigers weighing over 300 kg.
However, after the extinction of Epicyon, the last members of the second subfamily evolved to be smaller and primarily carrion eaters, weighing around 20-40 kg and adopting a diet similar to present-day hyenas. However, about 2 million years ago, they also became extinct due to competition from the feline family.
Just as the second subfamily and cats were locked in a life-and-death struggle, the third subfamily of the canine family - True Canine - quietly emerged. The third and second subfamilies almost appeared simultaneously, but the former developed stronger as time went on, while the third subfamily was suppressed and did not develop, thus maintaining sizes of only a few kilograms.
Characteristics of this third subfamily include slender necks and limbs, with the dewclaw regressed, and the remaining four toes more streamlined. Because of these features, paleontologists named them 'slender dogs.' Indeed, modern wild dog species such as wolves, foxes, and jackals also exhibit these characteristics, and all modern wild dog species belong to the True Canine subfamily.
The body structure of this subfamily made them weaker in terms of strength, but also more suitable for running. As the environment became more open and prey evolved faster, these features became important advantages. In the race with prey, the second subfamily with its large, clumsy body failed, while this third subfamily easily triumphed in hunting.
The failure of the second subfamily indicates that a large body size can lead to survival failure. From then on, in the world of giant land predators, dogs could no longer compete with cats, and cats became the largest predators, carnivores on land over 100 kg.
The True Canine subfamily followed a completely different evolutionary path from the previous subfamilies. They no longer attempted to compete in size with the feline family. Instead, they utilized their endurance advantage in long-distance running and ultimately succeeded. It can be observed that wolves and red foxes are the most widely distributed carnivorous species in the world today.
However, in terms of body size, the canine family always loses to the feline family. The third subfamily of dogs reached its maximum size at the end of the Pleistocene - the Dire wolf could weigh up to 80 kg. However, the saber-toothed tigers of the same period could weigh over 400 kg.
However, like the large dog subfamilies before them, the large cat species will ultimately become extinct. At the end of the Pleistocene epoch, 12,000 years ago, the environment underwent significant changes once again. Dominant cat species such as the saber-toothed tiger and the cave lion gradually became extinct. Among the species in the third subfamily, although the Dire wolf became extinct, the modern gray wolf survived and replaced the felines to become the strongest carnivore in North America. Although the wolf is not as strong as the tiger and lion in terms of body size, it can be said that in competition and evolution, the dog species emerged victorious in reclaiming North America.
And perhaps in the 17 million years of conflict between them, the hostility between the canine and feline families has been deeply ingrained in their genes. Today we can easily see domestic dogs and cats often fighting. Tigers and leopards enjoy killing and eating dogs. African wild dogs and wolves will always surround spotted hyenas when they spot them.
