Looking back at my most recent shoots, I think my average for a full day at a good zoo in decent weather is about 500 images. I would normally expect to get at least 20 really good images, by which I mean good enough to post here or on a photography website - although I don't think I have ever posted that many in the Gallery at one go. Incidentally I don't use my walls for hanging my own photos, instead I have reproductions of Julia Margaret Cameron, F H Evans, Art Kane and Man Ray for inspiration.
If I think a photo is going to work I will always take several exposures in fairly quick succession, minor variations in focus and framing and in the animal's pose can make all the difference between a reasonable image and a first rate one; I find that when I look carefully at the set of superficially similar images, there is usually one that clearly stands out.
If I know that there is a particular problem with a shot, such as needing to set an unusually slow shutter speed or to bracket exposures I will take extra shots to compensate for the ones that go wrong. Likewise if an opportunity is unlikely to be repeated, I will deliberately shoot more images because I'd much rather have too many than too few. For example when I went to Hayle in May I took about 100 images of the St Vincent amazon parrot in various poses - it's an old bird and the only one in the UK so I may never get another chance, the light was tricky and I knew that some of the images would be spoiled by shadows, by the wire of the aviary or by unsightly backgrounds, I was also experimenting with a new lens and I wanted to be very careful to use a range of exposure values to be sure of getting some shots with good highlight definition in the white feathers of the forehead.
Likewise on my last visit to Chester I took 77 photos in 7 minutes when the Indian rhino calf 'Komala' and her mother 'Asha' were chasing round their paddock and making the blackbuck herd run around too; in many, many years of zoo visiting I have never seen anything like it - so I took plenty of pictures, knowing that panning on fast moving animals inevitably risks problems with focus, awkward poses and cropped noses and tails. I had examples of all these faults, but no harm was done as I had some good ones too

Of course in the old days, I could only afford a couple of films per zoo visit, 75 images if I were lucky. That made me risk averse. I very rarely took more than 2 pictures of any animal and if the light was poor or the animal was not posing well I just moved on. With hindsight, I wish I had risked a few frames on the small-eared dog at the Jardin des Plantes in 1972 and the Hispaniolan solenodon at Frankfurt in 1973 and the birds of paradise and hummingbirds and Lear's macaws at Len Hill's Birdland and so on (eat your heart out TLD

). In other words, I don't regret taking too many photos, I now regret the ones I didn't even try to take

In those days the only photographers who could shoot hundreds of images in a day were pros whose clients had deep pockets and it's not surprising that their images were much better than the amateurs'. Now we can all shoot like that if we want to, for the price of a single memory card (if we have computer, software etc) consequently our pictures are getting better and photography as a profession is going the way of the dodo.
Alan