It’s no wonder we describe dogs as “man’s best friend.” As the oldest domesticated animals, dogs are smart and social, just like their wolf ancestors. Dogs and wolves are part of the diverse biological family of animals called Canidae.
But what makes an animal a “canid,” and more importantly, what specifically makes a domestic dog a canid? What characteristics do the different canid species share, and where do our pet dogs fit into it all?
What Defines Canids?
Let’s start with the basics in our family dog’s biological classification, or “taxonomy.” An animal that’s a member of the Canidae family on this taxonomy is called a canid. The Canidae family is further divided into subfamilies: Caninae, Borophaginae, and Hesperocyoninae. These last two subfamilies are extinct, while “Caninae” is where we derive the word “canine” to describe dogs.
We usually use the word “canine” to refer to a domestic dog, but dogs aren’t the only animals that are considered canines (or “canids”). Dr. Bridgett vonHoldt, Associate Professor in Ecology and Evolutionary Biology at Princeton University, explains that these biological families are “composed of dogs, wolves, coyotes, foxes, and jackals, with many more extinct lineages.”
The exact classification of canids is up for debate, but experts generally agree that there are around 35 species within the family. You can find wild canid species on all continents except Antarctica. “The family classification of Canidae is an umbrella term that collects many entities under its broad scope of being a canid following morphology, behavior, and evolutionary relationships,” Dr. vonHoldt explains.
There is also some debate when it comes to classifying domestic dogs. Some experts support dogs as a wolf subspecies (Canis lupus familiaris in Latin), while others categorize them as a separate canid species (Canis familiaris in Latin).
How to Tell Different Canids Apart
Canid Body Shape
When looking more closely at canids, we start with morphology. “Morphology” is the study of the way different organisms of a species are structured. Dr. vonHoldt describes canid morphology as a basic, “dog-like” shape. This dog-like shape typically includes a bushy tail, elongated skull, toe pads, the occasional presence of a dew claw, non-retractable nails, a baculum (penis bone) in males, arrangement of the teeth that makes it possible to cut through muscle and tendon, and a very strong bite force. While body shape is consistently “dog-like,” canids range widely in size. The smallest species, the fennec fox, weighs under 5 lbs, whereas gray wolves can weigh over 100 lbs.
Of course, following millennia of selective breeding, domestic dogs have lots of variation from the typical canid morphology. For example, bushy tails are common amongst spitz breeds (like the Norwegian Elkhound), but other breeds can have curled or short tails. Some dog breeds have drop, rather than erect ears, or shorter skulls. In fact, there’s more variation within domestic dog breeds than all the other species in the Canidae family put together.
The Canid Diet
Many small- to medium-sized canid species are opportunistic omnivores that will eat whatever they can. In contrast, larger canids, like wolves and dholes (a canid native to Asia), are pack-hunting carnivores. Domestic dogs are opportunistic omnivores, too—think about their counter-surfing tendencies—and commercial diets can contain a range of foods like fruit, vegetables, and cereals, as well as meat.
Canid Social Structures and Reproduction
When we think of species like wild dogs and wolves, we associate them with living and working in packs. While some canids are social, other canids—such as foxes and coyotes—are more solitary. Of course, domestic dogs fall into the social category, and that’s one of the things that makes them such exceptional companions.
One thing canids have in common, though, is how they reproduce and care for their young. When dogs mate, specific tissues in the male’s penis expand, and the female dog’s vagina contracts around it, resulting in the two animals becoming locked together for a short period of time, usually end to end. This process, called the “copulatory tie,” is common among canids. (You may surprise a pair of foxes in this situation in your yard one spring, and now you’ll know exactly what’s going on!) Canid matings produce “a litter of offspring with parental care until weaning and dispersal,” Dr. vonHoldt notes.
Domestic dogs share many visual, scent, and vocal communication methods with their wild canid counterparts. When observing dog body language, looking at changes in tail and ear position, facial expressions, eye contact, and various other subtle cues can tell you a lot about how a dog feels. Sniffing and territorial scent marking are common canid behaviors that you’ve no doubt seen your own dog display. And while howls and barks vary in volume, intensity, and style, they, too, are common canid behaviors.
Are Foxes Canines?
Sometimes people question whether foxes are dogs, and some people even ask, “Are foxes cats or dogs?” (Yes, this really is a common search term!) However, Dr. vonHoldt explains, foxes “can be referred to as canids because they are also a member of the Canidae family.” Just because they are canids, however, doesn’t mean that foxes are dogs. Foxes definitely aren’t dogs; foxes are wild animals, and they should only be cared for by qualified wildlife rehabbers when needed.
Are Hyenas Dogs?
Hyenas are often lumped into the canid category because of their behavioral and morphological similarities to dogs. Surprisingly, they are more closely related to cats than dogs! Technically, hyenas are neither canines nor felines, says Dr. Marc Bekoff, Professor Emeritus, Ecology and Evolutionary Biology at the University of Colorado. “They have their own family, the Hyaenidae,” he explains.
Which Canids Are Domestic Dogs Most Closely Related To?
Even though domestic dog breeds vary widely—from tiny Chihuahuas to giant Great Danes—they all come from the same ancestors and share 99.9% of their DNA with the gray wolf. “Dogs were domesticated from a lineage of gray wolves that are extinct,” Dr. vonHoldt says.
Despite dogs and modern gray wolves being cousins, the two canids usually don’t look much alike. This comes from humans selectively breeding dogs “for specific and exaggerated phenotypes,” Dr. vonHoldt notes. Phenotypes are observable traits that animals display, like the way it looks or how playful it is.
Domestic dogs have existed for thousands of years. But they still share their wolf ancestors’ social natures and intelligence: two traits that make them so attractive as companion animals.
Interbreeding Between Domestic Dogs and Wild Canid Species
Domestic dogs can and do interbreed with their wild canid relatives, producing fertile offspring. This could have surprising benefits—and drawbacks—in the future. As Dr. vonHoldt points out, interbreeding amongst non-domesticated canids “could provide a valid option for them to face climate change because the mixing results in a large boost of genetic variation and thus adaptive potential.” However, Dr. Bekoff notes that “it can be a problem because the hybrids can be a nuisance to humans and other animals in the wild.”
The interbreeding of domestic dogs with wolves creates exceptionally challenging (and illegal to own in many U.S. states) wolf-dog hybrids that are absolutely not an animal that the average pet owner should ever consider as a pet for their family. Sticking with recognized dog breeds raised by responsible breeders to avoid these controversial “pets.” And, providing you can offer the right training and enrichment, there are many smart, high-energy, wolf-like dog breeds out there that can be excellent companions for your adventures.