Most dogs who come through shelters are at least somewhat neglected, socially, physically and spiritually in their previous life.
They may have been stray, living on the streets living off what they could scavenge from trash bins and dumpsters if they were lucky, trying to catch voles, lizards and eating horse poop if they were not.

” Before”
Ellie came in from a rescued scenario and this is how she was living. She will probably always be somewhat shy but after some rehabilitation Ellie is now in her forever home and feels loved, goes on hikes in the Sierras off leash and enjoys playing with friends at the beach
So one of the things you may find is a certain possessiveness over food, toys or treats. This sometimes makes it unwise initially to be using food as a reward in training, you really don’t want to be refreshing those behaviors on a daily basis while the dog is anxious in its new environment. This is especially important if you have other animals or children in the home and food scraps are a factor in your daily life.
As the dog becomes calmer and starts to be sure of its food being available at the same time every day, preferably twice a day, then the neediness will fade in most dogs. It might then be appropriate to undertake a structured and supervised desensitization and counterconditioning program to change the habit. Whatever you do, do NOT start working the dog by teasing it with food too soon in the rehabilitation process. Giving it and taking it away. You might read somewhere that this will make the dog better. What it will do is get you or your children bitten! Food sensitivity is a huge trigger in dog bites and fights, ignore it at your peril.
If they were not scarred when they arrived, many dogs are traumatized by spending a couple of hours, days or weeks in a shelter. It is well known in shelters that the reason we kill so many is that the environment is so toxic most dogs go kennel crazy within three weeks anyway and can be labelled un adoptable.
Please don’t overwhelm the dog!
When your shelter dog arrives the biggest gift you can give is calmness, a loving environment and some rest and recuperation.
A consistent structure , timetable of regular exercise, feeding and settle down time will help the dog heal.
Some simple rules, timing of meals and quality of food will often see the dog looking completely different within a week or three.
Sometimes it takes longer, much longer, but it is imperative that you allow nature to do the healing. Remember that your expectations are not relevant to the process, in fact unrealistic expectations can sabotage the healing process. Healing is what needs to happen first.
If a dog is feeling scared, insecure and emotionally or physically injured, it is really hard for them to behave normally. They may be reactive or closed down.
Most of the behavior issues are anxiety related. Reduce the anxiety first, then wait. The behaviors will probably fade.
If the behavior persists then it may have become a habit. Habits can be modified with appropriate training. However if you try to modify a behavior using training but the behavior is the result of anxiety that is still present, first of all you will probably not be successful. You may see some initial change, the novelty value of the new attention, but the cause of the behavior, the anxiety, is still there and you will almost always get very strong regression as the anxiety re asserts itself.
Most of these behaviors are rewarding for the dog in some way, whether you like it or not or whether you believe it or not.
Future blog: How to teach your dog to say “Timmy is down the well”