I agree with both of the above posts EXCEPT cute healthy puppies of small breeds are never there after 30 days, they are snatched up immediately and most shelters even have waiting lists for small breed dogs, even adults. I also do rescue and while I agree, most people should spay and neuter, I am not going to tell them, what in this area and most places I have heard of, would be a lie.
I am under no illusions what happens at shelters and an old friend was mad at me when I told her frankly what happened to her old 11 year old, not housebroken, walked with a limp from an old injury after getting hit by a car, now had arthritis and was cranky with young dogs and kids, family dog they had taken to the pound because he got snippy with the new dachund puppy they got. Who, by the way, was still not house trained 2 years later, but was she was allowed to live in the house because she was so cute. The old dog had been left in the back yard when he couldn't be house trained, hmmm, seeing a pattern here, maybe it was the owners, not the dog??? Anyway, I couldn't believe they took him to the pound. Why not take him to the vet and have him humanely euthanized if you have to? Instead of dumping him in a scary place when it was going to happen anyway and he was left alone and terrified, feeling abandoned. She honestly thought they would find him a home!! I let her know that he was probably put down, if not immediately, than within days of her dumping him. She was not happy with me, but I am not the one that dumped my dog.
I know of a family here that found a stray kitten, decided they couldn't keep it. Took it to the pound, signed it over. There daughter was crying, very concerned, they staff promised to find it a home, etc. They walked out, the little girl continued to sob, the parents finally relented, walked back in 10 minutes later to reclaim the kitten and because they had turned it in, they consider it an owner surrender, they were overfull and put it down immediately. So I know it happens, strays they have to hold, not surrenders.