Frankly, I don't quite understand why zoos make such a big thing about the annual stocktake. It's necessary I agree but surely, in the case of most species, the records maintained by the zoo should provide accurate numbers anyway. Most species (fish and invertebrates excepted) are rarely maintained in huge numbers anyway, and the primate keeper (to give just one random example) surely knows how many Ruffed Lemurs he or she is in charge of without entering the enclosure with a clipboard to manually count them. Surely every morning each and every one is checked and accounted for anyway.