Every dog needs a collar, chiefly because they need something on which to hang their leash, license, ID and rabies vaccination tag.
There are so many styles of collar out there that it's easy to get one that reflects your dog's (or your) personality—but collars serve purposes beyond identification and decoration and not all kinds of collars are appropriate for all, or even any, dogs.
This is the standard collar for dogs. It has a buckle or plastic snap ("quick-release") closure and a ring for attaching identification tags and leash and is available in many colors and designs. A flat collar should fit comfortably on your dog's neck; it should not be so tight as to choke your dog nor so loose that they can slip out of it. The rule of thumb says you should be able to get two fingers underneath the collar.
The martingale collar is also known as a limited-slip collar. This collar is designed for dogs with narrow heads such as Greyhounds, Salukis, Whippets and other sighthounds. It is also useful for a dog of any breed who is adept at slipping out of their collar or for fearful dogs who may try to retreat while out on a walk. A martingale collar is a must-have for anxious and fearful dogs.
The martingale consists of a length of material with a metal ring at each end. A separate loop of material passes through the two rings. The leash attaches to a ring on this loop. When your dog tries to back out of the martingale, the collar tightens around their neck. If the collar is properly adjusted, it will tighten just to the size of your dog's neck, without choking them. This is the most humane collar option for dogs who may slip out of their collars.
The head collar is similar in principle to a horse's halter. One strap of the collar fits around your dog's neck and sits high on the head, just behind the ears. The other strap forms a loop around your dog's muzzle. The leash attaches to the ring at the bottom of the muzzle loop.
The head collar is good for strong, energetic dogs who may jump and/or pull. Because the halter is around your dog's muzzle, instead of their neck, your dog loses a great deal of leverage and they are unable to pull on the leash with the full weight of their body.
To be effective, the head collar must be properly fitted. As with any training equipment, the head halter is not intended to be used in a jerking or yanking fashion but rather to gently steer your dog in the direction you need them to go. Some manufacturers include instructions and a DVD with the collar. Otherwise, ask your dog trainer or a knowledgeable sales clerk for assistance with fitting. Proper fit and use should minimize the risk of injury to your dog.
It may take some time, patience and lots of treats to get your dog accustomed to wearing a head collar. Put it on them for short periods while giving your dog lots of high-value treats until your dog is comfortable in the collar. Then they should only wear it when you are taking them out on a leash. Don't leave the head collar on your dog all the time; eventually they will manage to pull off the muzzle loop and use it as their chew toy!
Aversive collars, or collars that rely on physical discomfort or even pain to teach a dog what not to do, are not a humane option. While they may suppress the unwanted behavior, they don't teach the dog what the proper behavior is and they can create anxiety and fear, which can lead to aggression. Positive reinforcement training methods—ones that use rewards—are more effective and strengthen the relationship between you and your dog.
Choke chain collars
As the name implies, this collar is made of metal links and is designed to control your dog by tightening around your dog's neck, an often painful and inhumane training tool. Unlike the martingale collar, there is no way to control how much the choke chain tightens, so it's possible to choke or strangle your dog. It can also cause other problems, such as injuries to the trachea and esophagus, injuries to blood vessels in the eyes, neck sprains, nerve damage, fainting, transient paralysis and even death. It is very easy to misuse choke chains and with all the humane, effective collars on the market, choke chains are unnecessary and should not be used.
Prong or pinch collars
The prong or pinch collar is similar in design to the martingale. However, the control loop that the leash is attached to is made of chain. The loop that fits around your dog's neck is made of a series of fang-shaped metal links, or prongs, with blunted points. When the control loop is pulled, the prongs pinch the loose skin of your dog's neck. Similar to choke chains, these collars can be easily misused and should not be used.
Shock collars use electric current passing through metal contact points on the collar to give your dog an electric signal. This electric signal can range from a mild tickling sensation to a painful shock. Shock collars may be sold as training devices, although more and more companies are pulling them from the shelves. They are also used with pet containment (electronic fencing) systems. Shock collars are often misused and can create fear, anxiety and aggression in your dog toward you or other animals. While they may suppress unwanted behavior, they do not teach a dog what you would like them to do instead and therefore should not be used.
Electronic fencing uses shock collars to deliver a shock when the dog approaches the boundaries of the "fenced" area. Typically, the shock is preceded by a tone to warn the dog they are about to get shocked. While the dog will be shocked if they run out through the electronic fence, they will also be shocked when they re-enter, leading to dogs who are unlikely to return home.