Sally, I lost my cat one summer and it was heartbreaking to know if the pound picked her up, they
only hold the animal for 3 days before they adopt them out. My cat was not microchipped and I went every 3 days to two different places (of course the county and the city don't work together). I had tickets to go on vacation in a month and had to finally decide to 1. cancel my trip to keep looking or 2. take the trip. I went on the trip but it kills me to think they may have found my cat while I was gone. (They refused to answer questions about incoming animals. I had to be there in person to check.)
Long story short, all those animals may not be abandoned.
On the flip side, I heard because of the downturn in the economy tons of horses are being abandoned. I assume other animals are as well.