Many people, myself included, use martingale collars as a training tool with our dogs. For those who don't know what I'm talking about, this is a martingale collar:
These collars are great for training purposes when your dog is on a leash. Unlike "choke chains", there is a limit to how much the martingale collars can tighten so your dog can't "choke out" like with a choke chain. Also, when you give a correction, the collar tightens and then releases immediately, so there is no sustained tension around the dog's neck (and for those of us who have reactive dogs, we know how important it is to avoid tension at all costs!!).
So what's the big deal about wearing a martingale collar at the dog park? What can happen is when dogs are playing and nipping and mouthing at each other's necks like this:
One dog's teeth can get stuck in the chain part of the other dog's martingale collar. When this happens, the dog who's teeth are stuck understandably starts to panic and roll around trying to get loose. If you take the chain of a martingale collar and twist it in circles, the chain can't release and the tension builds and builds and builds. As you can imagine, this creates an incredibly dangerous situation for the dog wearing the collar.
I know a woman who owns a dog daycare in Edmonton and this exact situation happened to her. The problem is that when both dogs are panicking, it's nearly impossible to intervene. In her case, the dog wearing the collar lost consciousness. The staff grabbed scissors and cut the collar off the dog, but by that time the dog had no pulse and wasn't breathing. The owner of the daycare, being a fellow Pet First Aid Instructor, performed CPR and was able to revive the dog (anyone interested in getting certified in Pet First Aid, click here). If she hadn't known how to perform CPR on a dog, the dog would have died all because he was playing with the wrong collar on.
A couple of days after I spoke with this lady about the situation, I almost had the same thing happen to my dog Aspen at the dog park. Luckily Aspen's martingale collar has a buckle (most don't), and she was playing right at my feet, so when the other dog's teeth got stuck in her collar, I was able to just reach down and unclip the buckle and no harm was done. Since that day I no longer allow dogs to wear martingale collars at the dog park when on my walks.
What if the only collar you have for your dog is a martingale? I have flat collars that I can put on your dog when we're at the park, but this isn't an ideal situation as my collars won't have your dog's ID tags on them. You can get a plain old flat collar for very cheap, and I would suggest getting a second pair of ID tags so your dog has ID on him/her regardless of what collar he/she is wearing.