Using ZTL: Meerkats are kept at 125 collections
Chapman's zebra:13
African elephant: 5
Asian elephant: 5
Giraffe: 28
Lion: 37
Tiger: 40
Jackass penguin: 9
Gentoo penguin: 5
Humboldt penguin: 38
King penguin: 2
Macaroni penguin: 2
Magellanic penguin: 1
Northern rockhopper penguin: 3
Little penguin: 1
Western rockhopper penguin: 1
American flamingo: 17
Andean flamingo: 1
Chilean flamingo: 30
Greater flamingo: 14
Lesser flamingo: 3
Puna flamingo: 1
Visitors can see a variety of species of monkeys, flamingos and penguins at UK zoos. There are too many meerkats and zoos could choose whether to have lions or tigers, rather than both.
I understand the problems of gene pools, but, as has been said in other forums, zoos should choose whether to keep genetically pure subspecies of some species and work out how to cut the number of hybrids (perhaps by ceasing breeding them) or to keep hybrids with high genetic variety and cut down the number of varieties. Trying to keep as many individuals as possible of some species impacts on other species, which are worth saving from extinction, even if the average zoo visitor doesn't come to see them.
I've seen sifakas in the wild. I went all the way to Madagascar to see lemurs.
Again, as I've previously mentioned, it would not matter what species of penguin or flamingo for example going off your list to the public. They lump them together as one, just as you have with giraffe, lion and tiger. With Penguins, whether its Humboldt, Rockhopper, King whatever, a penguin to most of the public is a penguin. I've heard people complain about Slimbridge saying all there is is Flamingos, despite all the separate species of Flamingo. This just does not really interest the average member of public.
Meerkats are of such a high number because they are relatively inexpensive to house, they are easy to manage, they are small and therefore do not require a vastly large space that some other species would, they are readily available to source due to the frequent reproduction and litter size and also most people have an idea what Meerkats are due to the adverts on TV. They draw people in and are a great marketing tool as kids lap up soft toys in the gift shop of them as well as providing quite an income for "Meerkat encounters" across zoos.
With Lions and Tigers or possibly more big cats in zoos, this is a great educational tool as you can compare cats, geographical ranges, needs, dietary requirements, social groupings, prey items. The lot. Having a pride of African Lions and then looking round and seeing solitary Snow Leopards or Sumatran Tigers are a huge educational message to the public. You need the animals there to engage most public unfortunately. Signage often doesn't get read, and without a visual, most public don't engage quite as much. Again thats from 17 years of seeing this first hand everyday.
Zoos are constantly working with TAG's and studbooks to source and hold genetically pure animals but unfortunately in this day and age, finding an animal that is above the 95% level of pureness is hard, even more so when a certain species or subspecies may only be held in several collections across the continent. All of these tactics you have stated such as not breeding hybrids do take place already. Yes granted not all are quite as rock solid for example we are still seeing hybrid Giraffe in the system, but with the help of BIAZA, we are working on that still.
The point to me of hybrids with high genetic variety also doesn't make much sense. If its a hybrid, its a hybrid and should not be bred off at all.