It鈥檚 no wonder we describe dogs as 鈥渕an鈥檚 best friend.鈥� 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 鈥渃anid,鈥� 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鈥檚 start with the basics in our family dog鈥檚 biological classification, or 鈥渢axonomy.鈥� An animal that鈥檚 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 鈥�Caninae鈥� is where we derive the word 鈥渃anine鈥� to describe dogs.
We usually use the word 鈥渃anine鈥� to refer to a domestic dog, but dogs aren鈥檛 the only animals that are considered canines (or 鈥渃anids鈥�). Associate Professor in Ecology and Evolutionary Biology at Princeton University, explains that these biological families are 鈥渃omposed of dogs, wolves, coyotes, foxes, and jackals, with many more extinct lineages.鈥�
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. 鈥淭he 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,鈥� 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. 鈥淢orphology鈥� is the study of the way different organisms of a species are structured. Dr. vonHoldt describes canid morphology as a basic, 鈥渄og-like鈥� 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 鈥渄og-like,鈥� 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鈥檚 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鈥攖hink about their counter-surfing tendencies鈥攁nd 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鈥攕uch as foxes and coyotes鈥攁re more solitary. Of course, domestic dogs fall into the social category, and that鈥檚 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鈥檚 penis expand, and the female dog鈥檚 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 鈥渃opulatory tie,鈥� is common among canids. (You may surprise a pair of foxes in this situation in your yard one spring, and now you鈥檒l know exactly what鈥檚 going on!) Canid matings produce 鈥渁 litter of offspring with parental care until weaning and dispersal,鈥� Dr. vonHoldt notes.
Canid Communication
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鈥檝e 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, 鈥淎re foxes cats or dogs?鈥� (Yes, this really is a common search term!) However, Dr. vonHoldt explains, foxes 鈥渃an be referred to as canids because they are also a member of the Canidae family.鈥� Just because they are canids, however, doesn鈥檛 mean that foxes are dogs. Foxes definitely aren鈥檛 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 , Professor Emeritus, Ecology and Evolutionary Biology at the University of Colorado. 鈥淭hey have their own family, the Hyaenidae,鈥� he explains.
Which Canids Are Domestic Dogs Most Closely Related To?
Even though domestic dog breeds vary widely鈥攆rom tiny Chihuahuas to giant Great Danes鈥攖hey all come from the same ancestors and share 99.9% of their DNA with the gray wolf. 鈥淒ogs were domesticated from a lineage of gray wolves that are extinct,鈥� Dr. vonHoldt says.
Despite dogs and modern gray wolves being cousins, the two canids usually don鈥檛 look much alike. This comes from humans selectively breeding dogs 鈥渇or specific and exaggerated phenotypes,鈥� 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鈥� 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鈥攁nd drawbacks鈥攊n the future. As Dr. vonHoldt points out, interbreeding amongst non-domesticated canids 鈥渃ould 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.鈥� However, Dr. Bekoff notes that 鈥渋t can be a problem because the hybrids can be a nuisance to humans and other animals in the wild.鈥�
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 鈥減ets.鈥� 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.