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Canidae

life science Maturity 7-9 Next article →

Canidae is a biological family of carnivores that includes many familiar animals. This group is a clade, which means they share a common ancestor. Most people simply call these animals canids or dogs.

Dogs, jackals, wolves, and foxes (Plate X)
Dogs, jackals, wolves, and foxes (Plate X)

The family is divided into three subfamilies. Two of these, the Hesperocyoninae and Borophaginae, are now extinct. The only living subfamily is the Caninae. This group includes wolves, foxes, coyotes, and domestic dogs. Canids are found on every continent except Antarctica. Some reached new lands by traveling alone. Others arrived by accompanying human beings over long periods of time.

Canids share several physical traits that help them survive. Most have long muzzles and upright ears. They possess long legs and bushy tails. Their teeth are specially adapted for slicing flesh and cracking bones.

Hesperocyoninae, Borophaginae & Caninae
Hesperocyoninae, Borophaginae & Caninae

Most canids are digitigrade, meaning they walk on their toes. Their nose tips and foot pads are always naked. Most have five toes on their front feet. The thumb, or pollex, is usually reduced. Most have four toes on their hind feet. Some domestic dogs have a vestigial fifth toe called a dewclaw. These body forms are built for chasing prey.

Many canids are highly social animals. They live in family units or small groups. They often behave cooperatively to survive. Typically, only the dominant pair in a group breeds. They usually rear a single litter of young each year in an underground den. Canids use vocalizations and scent signals to communicate with one another.

The domestic dog is unique because of its symbiotic relationship with humans. This relationship began with Upper Paleolithic humans. Today, it is one of the most widely kept domestic animals.

The history of canids began in North America during the Late Eocene. This was between 37.8 and 33.9 million years ago. The first identifiable member was Prohesperocyon wilsoni. Fossils of this animal were found in southwest Texas. Scientists identify it as a canid by its middle ear structure. It had an enlarged bulla, which is a bony structure protecting the ear. It also lacked the upper third molar. This loss helped create a more shearing bite.

Hesperocyon (white background)
Hesperocyon (white background)

Early canids also had toes that were parallel and closely touching.

As time passed, the family split into three distinct subfamilies. The Hesperocyoninae lived from about 39.74 to 15 million years ago. The Borophaginae appeared between 34 and 32 million years ago.

Aelurodon illustration
Aelurodon illustration

The Caninae subfamily appeared between 34 and 30 million years ago. The success of the Caninae was linked to their teeth. They developed lower carnassials that could both shear meat and perform mastication, or chewing. Around 8 million years ago, a land bridge called Beringia allowed the genus Eucyon to enter Asia. Later, the formation of the Isthmus of Panama about 3 million years ago allowed canids to move into South America.

Canids show incredible variety in size and habitat. They live in deserts, forests, tundras, and savannas. The fennec fox is very small. In contrast, the gray wolf is much larger and can weigh up to 80 kilograms.

Hesperocyoninae, Borophaginae & Caninae
Hesperocyoninae, Borophaginae & Caninae

Some species, like the bush dog, have shorter legs. Others, like the maned wolf, have very long limbs. A few species are even able to climb trees. These include the raccoon dog and the gray fox. This diversity allows them to inhabit almost any temperate or tropical environment.

Evolutionary studies of canids have changed over time. Scientists used to study them through morphology, which is the study of physical forms. Now, they use molecular studies to look at DNA. These studies help map phylogenetic relationships, or how species are related. Genetic studies show that some species have large hybrid zones. This happens because of high levels of gene flow between populations. This modern science helps us understand how the diverse world of canids came to be.

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🖼️ Images & Media (7)
File:Ailurus fulgens - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam -(white background).jpg
Ailurus fulgens - 1700-1880 - Print -...
File:Hesperocyon (white background).png
Hesperocyon (white background).png
File:Aelurodon illustration.png
Aelurodon illustration.png
File:Dogs, jackals, wolves, and foxes (Plate X).jpg
Dogs, jackals, wolves, and foxes (Plate X).jpg
File:Hesperocyoninae, Borophaginae & Caninae.jpg
Hesperocyoninae, Borophaginae & Caninae.jpg
Red_Fox_(Vulpes_vulpes)_(W1CDR0001529_BD12).ogg
File:BedaleHunt2005.jpg
BedaleHunt2005.jpg
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