The Nanaimo branch has a system to track every animal that comes into their system. I was particularly interested in this because another branch just uses loose sheets of paper for surrendering animals, which are not numbered nor is there a bound register of the animals surrendered that I was able to ascertain.
As I recall, Nanaimo uses a book of numbered pages with copies that are left in a Bound Book and each animal is listed when it comes in and the reason (stray, surrender). This number follows the animal through the system whether it goes to foster, adoption, has young, transferred etc.)
I was impressed with the system they used.