Wolves and dogs are strikingly similar.  Long thought of as the ancestor of the domestic dog, they are now believed to be cousins, both descended from a common wolf-like ancestor.  They share so many physical and behavioural traits that, historically, behaviourists have drawn conclusions about dogs from studying wolves. The period of domestication, selection and evolution has led to some significant differences too.

There are some obvious behavioural differences between wolves and dogs; wolves kill their own food and tend to avoid people. Dogs, by contrast, look for humans to provide food.  In turn, this means that they eat differently; dogs are scavenging omnivores whereas wolves are carnivorous predators.

Socially there are differences too, wolves are highly territorial whereas dogs either share their territory with humans or live on the periphery of human settlements.  Dogs tend to bark as adults whereas adult wolves rarely bark as adults.  Wolves use a range of howling sounds to communicate which dogs do not.

Dogs are more social with humans, but wolves are brighter.  Well really both are highly social, however, domestic dogs have an innate ability to understand humans more easily than their wild cousins.  Several studies do show that even hand-reared wolf pups do not show the same kinds of attention seeking and affectionate behaviour that domestic dog breeds show.  The corollary to this is that dogs perform worse than wolves in independent problem-solving tasks; they have evolved highly specific social skills for working with humans and as a consequence of this lost some of their cognitive skills.   It is our hyper-social behaviour which may have linked our two species.

Physically wolves are larger, with a larger head in comparison to its body.  Their jaws and teeth are larger, with a higher crush strength!   Wolves have chests and hips which are narrower and their ears always erect, whereas many domestic dogs have at least partly floppy ears.  Eye colours in dogs vary over a wide range, however, wolves eyes are always shades of yellow or amber.   Dogs reach sexual maturity earlier, usually at 6 to 9 months whereas wolves reach sexual maturity at 18 to 24 months. 

They are strikingly similar; they have interbred both in the wild and now, domestically too.  But the biological and behavioural difference make them more dissimilar than two different dog breeds, in ways that are significant given how domestic dogs now live in mixed species groups with humans.   Would you want a wolf-dog as a pet?