Are Bears Related to Dogs? 8 Things to Know
A bear can look remarkably like a very large dog. There is a real family connection, but it goes back more than 40 million years, and bears have closer relatives that may surprise you.
The long muzzle, the padded paws, the wet black nose, the way a cub wrestles with its brother and then flops over to be scratched. It is easy to see why people look at a bear and wonder whether it is simply a giant dog.
The short answer is that bears and dogs are related, but only as distant cousins. They belong to the same large branch of the mammal family tree, and they share an ancestor that neither of them much resembles. They cannot interbreed, and neither one descends from the other.
The longer answer is more interesting. It takes in a small tree-climbing hunter from the age just after the dinosaurs, a group of extinct giants with a misleading name, and the awkward fact that a bear's nearest living relatives include an animal with flippers.
Here are eight things worth knowing.
Read all the way to the end. We save the panda question for last, and the answer surprises most people.
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The family tree
1. They share a branch
Did you know this?Bears and dogs both belong to the order Carnivora, the group of roughly 280 living mammal species that also includes cats, seals, weasels and hyenas. Membership has nothing to do with eating meat. It is a matter of descent, marked by a shared feature of the teeth that the first members had and some later ones lost.
Early in its history the order divided into two great branches. One is Feliformia, the cat-like carnivores: cats, hyenas, mongooses and civets. The other is Caniformia, the dog-like carnivores. That branch holds the dog family, the bear family, the seals, sea lions and walrus, and the large group made up of weasels, otters, badgers, raccoons, skunks and the red panda.
AdvertisementSo a bear and a dog sit on the same side of that first fork. A hyena, for all that it looks like a dog, sits on the other side with the cats. This means a grizzly is more closely related to a poodle than a hyena is, and more closely related to a poodle than to a lion.
Scientists tell the two branches apart partly by a detail of the skull. The bony capsule that houses the middle ear is built differently in cat-like and dog-like carnivores, and bears and dogs share the dog-like pattern.
AdvertisementIn plain termsBears and dogs are on the same half of the carnivore family tree. Cats and hyenas are on the other half. -
The timing
2. They split more than 40 million years ago
Did you know this?The cat-like and dog-like branches parted company early, more than 50 million years ago. Not long afterward, on the dog-like side, the line leading to wolves, foxes and domestic dogs went its own way. That separation happened well over 40 million years ago, during the Eocene, when the world was much warmer than today and forests reached the Arctic.
AdvertisementThe dog family is therefore the oldest surviving branch of the dog-like carnivores. The earliest known member, a slender, fox-sized animal called Hesperocyon, lived in North America about 40 million years ago, and the family stayed on that continent for most of its history before spreading across the world.
Everything else on the dog-like side, the ancestors of bears, seals, weasels and raccoons, carried on together for several million years before dividing in turn. The first animals that can fairly be called bears appear later still. They were small, and for a long time they were not very bear-like. One early genus, Ursavus, was about the size of a medium dog some 20 million years ago.
AdvertisementTo put that in scale: our own species is about 300,000 years old. Bears and dogs had already been on separate paths more than a hundred times longer than that before the first human walked.
Bears and dogs had been going their separate ways for over 40 million years before the first human being walked the Earth.
In plain termsThe dog line and the bear line have been apart far longer than humans have existed, and longer than there have been open grasslands for a wolf to run on.Advertisement -
The ancestor
3. It was small and lived in trees
Did you know this?The common ancestor of bears and dogs looked like neither. It was one of the miacids, a group of early carnivores that lived in the forests of North America, Europe and Asia from roughly 60 million to 34 million years ago, in the first chapters of the age of mammals.
A typical miacid was the size of a weasel or a marten. It had a long body, a long tail, short legs and flexible ankles and wrists suited to climbing. It hunted insects, lizards, birds and small mammals among the branches, and its brain was small by modern standards.
AdvertisementWhat marked it as a relative of every later dog, bear and cat was its teeth. Miacids had carnassials, a pair of blade-like cheek teeth, one upper and one lower on each side, that slide past each other like scissors to slice flesh. That shearing pair is the signature of the order Carnivora.
Paleontologists now treat the miacids as a loose collection of early forms, not a single tidy family. Some of them lie close to the origin of all modern carnivores. The important point holds: the shared ancestor was a small, agile, tree-climbing predator, and the bulk of a bear and the long running legs of a wolf both came much later.
AdvertisementIn plain termsPicture something like a pine marten. That is closer to the ancestor of bears and dogs than either a bear or a dog is. -
The surprise
4. A bear's closest relatives include seals
Did you know this?Ask which living animals are nearest to bears and the answer is not dogs. Once the dog family had branched off, the remaining dog-like carnivores formed a group that scientists call the arctoids, a name that means bear-like. It has three parts: the bears, the pinnipeds, and the weasel and raccoon group.
AdvertisementThe pinnipeds are the seals, sea lions and the walrus. They descend from bear-like land carnivores that took to the water more than 25 million years ago. Fossils of early forms show an otter-shaped animal with four working legs and webbed feet, halfway between shore and sea.
The weasel and raccoon group is the largest of the three. It holds weasels, otters, badgers, wolverines, skunks, raccoons, coatis and the red panda.
AdvertisementDNA comparisons confirm what anatomy suggested. Bears, pinnipeds and the weasel and raccoon group are all closer to one another than any of them is to a dog. A sea lion barking on a pier is nearer kin to a grizzly than a German shepherd is.
You can see it if you look. A seal's skull is strikingly like a small bear's, and a walrus resting on a beach has much the same heavy, flat-footed build as the bears it is related to.
AdvertisementA sea lion barking on a pier is closer kin to a grizzly bear than any dog is.
In plain termsDogs are family. Seals, sea lions, walruses, weasels and raccoons are closer family. -
The confusion
5. Bear-dogs and dog-bears were two different things
Did you know this?Two extinct groups have names that muddle the question, and they are often mixed up with each other.
The bear-dogs, known formally as the Amphicyonidae, were a separate family of dog-like carnivores. They appeared more than 40 million years ago and lasted until several million years ago, spreading across North America, Europe, Asia and Africa. The early ones were small. The later ones were formidable, with the largest matching a big brown bear in weight. They combined a wolf-like head and teeth with a heavy, bear-like body and a flat-footed walk, which is how they got their name. They were neither bears nor dogs. The whole family died out and left no descendants.
AdvertisementThe dog-bears, the Hemicyonidae, are a different story. They belonged to the bear side of the tree and are usually treated as an early offshoot of the bear family itself. But they did not look the part. Dog-bears such as Hemicyon were long-legged, ran on their toes like a wolf and had teeth built for meat. They lived mainly during the Miocene and also vanished without descendants.
AdvertisementBetween them, the two groups show that the body plans we call dog and bear are not fixed. Evolution produced heavy, bear-shaped relatives of the dog and lean, dog-shaped relatives of the bear, and both designs eventually disappeared.
In plain termsNo living animal is half bear and half dog. Bear-dogs were a separate extinct family, and dog-bears were an extinct running branch of the bears.Advertisement -
The likeness
6. They kept some family traits
Did you know this?The resemblance between a bear and a dog is not an illusion. Much of it is inherited from their shared ancestry among the dog-like carnivores.
Both have a long muzzle. Inside it sits a large set of thin, scrolled bones covered in scent-detecting tissue, and both animals live by their noses. A bear's sense of smell is even keener than a bloodhound's, and a bear can pick up a carcass from miles away.
AdvertisementBoth have claws that cannot be drawn back into sheaths. A cat's claws stay sharp because they are tucked away when not in use. A bear's or a dog's are always out, and wear blunt on the ground, which is why both leave claw marks in their tracks.
Both have the same basic set of teeth. The full count in dogs and in most bears is 42, more than a cat's 30, with large canines in front and broad molars behind. Male bears and male dogs also share a bone in the penis, the baculum, found throughout the dog-like carnivores.
AdvertisementAnd both are flexible feeders. Wolves and coyotes eat fruit, and foxes eat a great deal of it. Bears have simply taken that family habit further than any other member.
In plain termsThe resemblance is real. Long snout, fixed claws, 42 teeth and a superb nose all come from the same distant ancestors. -
The differences
7. Teeth, feet and diet tell them apart
Did you know this?Forty million years of separation show most clearly in three places.
AdvertisementThe first is the feet. Dogs are digitigrade: they stand on their toes, with the heel raised off the ground, which lengthens the leg for running. Bears are plantigrade. They set the whole sole down, heel included, as people do. That gives a bear stability and lets it stand upright, but costs it stamina. A bear can sprint at 30 miles an hour or more over a short distance. A wolf can trot all day.
AdvertisementThe second is the teeth. A dog's carnassials are still sharp blades for slicing meat. In bears those teeth have lost their edge, and the molars behind them have become broad and bumpy, built for crushing and grinding plants, nuts and insects.
The third is diet. Most members of the dog family are primarily hunters. Most bears are omnivores that eat far more vegetation than meat. The polar bear, a seal specialist, is the exception at one end, and the bamboo-eating giant panda is the exception at the other.
AdvertisementThere are quieter differences too. Bears have five toes on every foot, while dogs bear weight on four. Many bears sleep through the winter in a den, something no dog does. Bears and dogs cannot interbreed: a domestic dog has 78 chromosomes, and most bears have 74.
In plain termsLook at the tracks. A dog leaves four toes and no heel. A bear's hind print shows five toes and a long sole, and looks oddly like a human footprint.Advertisement -
The pandas
8. One is a bear and one is not
Did you know this?For more than a century zoologists argued over where the two pandas belong. The giant panda looks like a bear but eats bamboo and has a peculiar thumb-like wrist bone. The red panda is a cat-sized animal with a ringed tail, like a raccoon's. Were they both bears, both raccoons, or a family of their own?
Genetic evidence settled it. The giant panda is a true bear. It is the oldest surviving branch of the bear family, having split from the line leading to the other seven living bear species roughly 20 million years ago. That early departure explains why it looks and behaves a little differently from its relatives.
AdvertisementThe red panda is not a bear at all. It is the only living member of its own family, the Ailuridae, and it sits within the weasel and raccoon group. Its nearest relatives are raccoons, skunks and weasels.
The two pandas share a name, a diet of bamboo and a false thumb, an enlarged wrist bone that helps them grip stems. They evolved that thumb independently. Both are dog-like carnivores, so both are distant cousins of the dog, the giant panda by way of the bears and the red panda by way of the raccoons.
AdvertisementIn plain termsThe giant panda is a real bear. The red panda is its own family, closer to a raccoon than to any bear.
The short version
Bears and dogs are related, but distantly. Both are dog-like carnivores, on the opposite side of the family tree from cats and hyenas. They descend from a small, tree-climbing predator that lived more than 40 million years ago, and the dog line broke away first.
Since then bears have stayed closer to seals, sea lions, walruses, weasels and raccoons than to any dog. The extinct bear-dogs were a separate family, and the extinct dog-bears were a running offshoot of the bears. The giant panda is a true bear. The red panda is not.
What bears and dogs still share, the long snout, the fixed claws, the 42 teeth and the extraordinary nose, is a family inheritance. What divides them, flat feet against toes, grinding molars against slicing blades, is the work of a very long time apart.
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