i find this thread fascinating.
i have found over the years that...
large animals captivate people
moving animals big or small captivate people and hold their attention
walk-thru environments tend to hold peoples attention for longer periods
any form of interaction...real or perceived holds peoples attention
and immersion exhibits tend to slow down the pace at which visitors move through an exhibit. beautiful buildings/authentic archtecture and realistic plantings hold attention and can be as interesting to people as animals themselves.
older style zoo exhibits, lack of shelter, weather, repetition (rows of aviaries, vivariums/aquariums) and high visitor numbers in confined space, expectations and the pre-conceived views of visitors (is it worth looking for a mountain chicken?) all limit dwel time.
with that in mind i think its so important that zoos create enviroments, not just enclosures. interp hubs are best located under shelters, near seating and in areas where animals are normally in view. or at other points of high interest....for example, an artificial leopard above the chital deer exhibit in Taronga's wild asia always attracts attention leading most people to read the nearby signs. if zoos are to contribute to conservation education obviously they need to maximise dwell time and sustain interest. to do this, animals need to be placed in realistic habitats which extend to visitor areas. the visitors need to be comforable and feel relaxed about spending time there. distractions, whether it be noisy children in acoustically harsh viewing galleries or a food outlet next to a lesser exhibit such as say, deer etc (animals with typically low dwell time) need to be minimised. for this reason, i think immersion exhibits do well because they remove people from main boulevards. reptile houses, in contrast, often channel large numbers of people into squashy indoor areas with long rows of matching terrariums. even within taronga's serpenteria, which has two typical galleries, larger outdoor encloures and what was supposed to be a butterfly habitats. people tend to hang around in the butterfly exhibit which isnt cramped, is well lit and nice enclosures. in the other galleries, the only difference is that instead of a more spacious area its viewing areas are long, straight and narrow. dwell time drops. contrast this with say, Barcelona Zoo's spacious, lush and interesting reptile house and you see major differences in dwell time.
as Bill Conway pointed out in his 'how to exhibit a bullfrog' thesis, any animal can be made into a star. but designing an enclosure with long dwell-time clearly isnt just about even meeting animal welfare; its about designing an environment which engages people with the animals.