Everyone is familiar with the idea of zoos being referred to as ‘modern-day Noah’s arks’. Normally, the comparison is a favourable one, highlighting the work of zoos in saving species from extinction. But another parallel can be drawn which reveals zoos in a somewhat less favourable light.
In the numerous representations of the ark story, from mediaeval manuscripts through to modern children’s books and toys, almost all of the animals depicted generally come from a limited range of large and easily-recognised mammals such as lions, elephants, giraffes, zebras, bears, camels – precisely the sort of species sometimes rather disparagingly referred to by zoo people as ‘Noah’s ark animals’. Most good zoos, of course, try to include as many species as possible from outside this narrow range: there are probably very few collections in which the average visitor could immediately recognise and name all the species exhibited. How far, though, do any zoos go towards presenting a really balanced picture of the world’s biodiversity? The answer has to be that they don’t even try.
Almost all zoo collections are heavily biased towards the megavertebrates – in other words, towards a minority within a tiny minority of the world’s animal species. Take mammals, for example. Bearing in mind the enormous number of bat and rodent species, anything down to the size of a rabbit should be regarded as a relatively large mammal: how many small mammal species, then, can be seen in the average zoo? Again, the passerines outnumber all the other bird orders put together, yet make up perhaps 20% of the bird species held in zoos (by my very rough estimate, based on the breeding statistics in one volume of the International Zoo Yearbook). For reptiles, amphibians and fishes, zoo holdings are certain to be even less representative. And when we come to the ‘invertebrates’ – more precisely, the animals belonging to the 30 or so phyla other than the Cordata – the imbalance takes an exponential leap. Admittedly, hundreds of these species can be viewed in captivity, but again they are a greatly skewed sample – at a guess, maybe half of them are butterflies. Only six invertebrate phyla are included in ISIS listings: presumably none of the others have any significant presence in zoos. And one of the listed phyla, the Porifera (sponges), has just 11 of its c. 5,000 species held in a total of only nine ISIS-subscribing collections.
Does this matter? I think perhaps it does (though I admit it may be some way down the average zoo director’s list of priorities). It is instructive to picture an imaginary zoo displaying a representative cross-section of the million-plus described animal species. If it had a thousand species in all, these would include about 750 insects (300 of them beetles), 100 molluscs, eight birds and four mammals, making the collection as a whole, in film jargon, ‘very poor box-office’. This is of course a reductio ad absurdum: but some relatively small changes to the current distorted holdings might help zoos to give their visitors a slightly clearer picture of the animal kingdom – for example, by showing at least a few species from lesser-known phyla. (The Tardigrada or ‘water bears’ might be one good choice, being both weird and curiously endearing in appearance: they are minute, but the largest ones could be viewed under magnification in the way successfully used for, e.g., leaf-cutter ants.) With good explanatory material, such exhibits could enhance zoos’ educational role by helping people to realise that biodiversity isn’t just about Noah’s ark animals.