It's All In the Mix

Mixed-species exhibits are becoming increasingly popular in zoos around the world.  A major challenge for zoo directors seeking to attract crowds is to create new and exciting ways of displaying their animals.  Creating panoramas of mixed-species exhibits is a popular method of doing this.  Many successful combinations have been created - giant anteater and maned wolf, white rhino and plains zebra, binturong and small-clawed otter.

Other attempts have failed - polar bears were attempted with Arctic foxes at one zoo.  It worked out great for a while, with the foxes easily staying out of reach of the bigger, slower bears... until a fox slept in late one day in a spot that the bears could reach.

So what does it take to make a mixed-species exhibit successful?  Here are some tips:

1.) Don't mix predator and prey - seems obvious enough.  Shark and crocodilian exhibits tend to be the exception, with lots of fish sharing space with the predators, but these fish are often too small and too quick for the predators to seriously pursue.  Other than that, don't place an animal in an exhibit with animals it may want to eat.  Even if it never tries to go after an exhibit-mate, the stress it will put its roommates through will be severe.

2.) Build with both species in mind - don't create an exhibit for one animal and then attempt to squeeze in a second as an afterthought.  Each species has its own specific needs in captivity, and the exhibit should be made to accommodate the needs of every animal it houses.  Above all, the exhibit should be large enough to accommodate both species - even the most placid animals can get edgy in close-quarters.  The exhibit should allow all species present to be housed in socially-appropriate (ideally breeding) groups.  Tall African storks, like the marabou and the saddle-billed stork, don't usually breed when displayed in open exhibits with antelope and other ungulates - they probably, then, shouldn't be kept in these conditions.

3.) Reduce competition with multiple niches - Combine an arboreal species with a terrestrial one, or a terrestrial one with an aquatic one.  Try pairing a diurnal animal with a nocturnal one.  By placing animals with dissimilar habitats together, you reduce competition and make for more efficient use of the exhibit space (i.e., animals using different levels).  If you do have animals of the same niche - such as two diurnal grazing mammals - consider animals of differing sizes.

4.) Avoid closely related species, especially ones that look like one another - they will either view each other as rivals and fight, or will interbreed.  With some species this can work out fine - many zoos and aquariums display mixed-species flocks of flamingos, or penguins, or example, which are intensely social and unlikely to fight with members of a closely related species.  If these cases, it can work fine if you make sure that all species present are in appropriate social groups, including breeding opportunities.  Given the option, most species will take a mate true to their type.

5.) Beware of aggressive species - some animal are just aggressive.  Zebras, for instance, can be vicious towards small antelope.  I've seen a breeding male guanaco (wild llama) pick up a deer fawn in its mouth and throw it, for no apparent reason.  Primates tend to be a problem, as their curiosity leads them to harass other animals (not that there haven't been successful mixed-exhibits with primates).  Sometimes, a small aggressive animal can be successfully displayed with a larger, more placid species.  Some European zoos, for instance, display even-tempered Andean bears with small, pushy coati.  Always make sure that smaller species have a place to go where larger species can't follow (an example would be a separate section of the exhibit with a small doorway that only smaller animals could pass through).

6.) Remember that circumstances change - the success of your exhibit isn't just about species, it's about individuals, and the circumstances of individuals.  Each change, whether in the composition of the group or in the exhibit itself has the potential to alter the equilibrium of the display.  Whenever changes - new animals, births, removal of animals, etc - occur, make sure to monitor the display vigilantly.  

7.) Let there be a reason - other than just saving space.  Are animals being displayed together for educational purposes?  Then let there be a message, whether geographic (and please let the animals actually be ones that would live near each other in the wild... not just "African") or ecological (nocturnal display, desert display, etc).  The National Zoo's Small Mammal House features Malagasy lemurs, Asian deer, and South American birds in an exhibit together... no real reason, it seems, other than they could be housed together safely.  I suppose I could design an exhibit that would be suitable for African elephants and wolverines... but that wouldn't make sense as an exhibit.  So I don't...

Mixed-species displays can be a wonderful addition to a zoo.  They can also be a disaster.  As in most things, the difference comes down to planning.