It's What's For Dinner...

"... not for some years yet was any gorilla to be kept alive for more than a matter of months in captivity.  No doubt the diet tried out on some of these vegetarians - the daily ration at one zoo consisted of two sausages and a pint of beer in the morning, followed later in the day by cheese sandwiches, boiled potatoes and mutton, and more beer - contributed substantially to the premature decease of several of them."'

-Wilfrid Blunt. The Ark in the Park: The Zoo in the Nineteenth Century

A giant anteater may consumer 30,000 ants or termites in one day.  That, not to belabor the obvious, is a lot.

This begs the question, of course - where do you get that many ants and termites to feed a zoo anteater, especially in winter with a foot of snow on the ground?  The answer is simple.  You don't.

One of the major challenges of caring for zoo animals, especially in the early years, was what to feed them.  For some species, this is due to the fact that nobody really knows what they eat in the wild.  In cases such as these, the common practice was to guess, feeding the animals a diet that was deemed appropriate for a similar, known animal.  Sometimes this worked.  Sometimes it didn't.  Maned wolves, for instance, look like wolves, but whereas the later are primarily carnivores, the former eat a lot of plant matter.  Diseases caused by an excess of protein in the diet were one of the major early hurdles to the diet.  Or, for that matter, consider the case of the gorilla in the quote above.

If you do know what the animal eats in the wild, then it's simple... feed it that!  Well, not always "simple", exactly.  First of all, the wild food might not be available.  The keeping of koalas in US zoos, for instance, is still pretty much limited to those zoos who can get the eucalyptus for them.

Besides, what we think of as "the same thing" might not, in fact, be "the same thing" to the animal that eats it.

A parrot eats figs in the wild, so we feed it figs... but the figs we get at the grocery store are cultivated for human consumption, so they have a different nutritional content (usually higher in sugar) than wild figs.

A pelican eats fish in the wild, so we feed it fish... but unless we're in a position to get fresh fish daily, the ones we feed it are frozen first, which cause it to lose some of its nutritional value.

A python eats a rat in the wild, so we feed it a rabbit... but the rat we feed out was raised on a farm, so it's been eating a commercial lab diet, not a wild rodent diet.

And so on.

There are also going to regional differences.  Fruit and vegetables available to a zoo in California are going to be different (even if they're ostensibly the same kind) from those in Massachusetts.   Meat raised on two different farms may be entirely different.  You can try making a substitute - going back to anteaters, zoos used to feed minced meat, beaten with eggs and milk.  But how do you know then if you're getting it right?

In an effort to create uniformity, many zoos have turned to commercially prepared diets from companies such as Purina, Mazuri, and Zupreem.  Anteaters and aardvarks eat Insectivore Chow, made of ant-sized pellets.  There is Parrot Chow, Monkey Chow, Crane Chow, Rodent Chow, and a whole host of other chows, some of which you would never expect.  I remember standing if front of three hungry Nile crocodiles, the largest of them 14 feet long, looking at the nugget of Mazuri Crocodilian Diet in my hand.  It looked like charcoal, it smelled foul, it felt gritty, and I thought "There is no way that they'll eat this."  They loved it, showing an enthusiasm for it that I'd never seen them show towards fish, rabbits, guinea pigs,or other more "natural" diets.  And according to the vet, it was healthier.  Who'd a thought...

Zupreem Parrot Maintenance... "Taste the Rainbow"

There is a lot to be said for chow.  It's uniformity makes it a lot easier to know exactly what you are putting into your animals' bodies, and that different zoos know they'll be feeding the same diet.  It's easier to transfer and store, and doesn't spoil (I mean, it will eventually go bad, but not in the timeline that any zookeeper really needs to worry about).   It's a lot easier to quantify how much an animal is being given and how much it is eating, since dry chow is a lot easier to weigh and measure than fruit, vegetable, and meat.  Incidentally, it's also cheaper in the long run...

There has recently been something of a push-back against the kibble movement.  What the old-fashioned diets lack in exact nutritional perfection, they do make up for with enrichment value and encouraging natural behaviors.  Some animals, especially herbivores, spend most of their waking hours feeding.  If you give them a super-nutrient-rich diet that lets them get all of their caloric intake in half an hour, what will they do for the rest of the day?  Sure, you can give them enrichment and puzzle feeders and training and all that, but what better enrichment than letting them do what they would be doing naturally, anyway?  Some zoos have gone so far as to put their animals on the Paleo-Diet: if the wild animal wouldn't recognize it as food, they zoo animal shouldn't either.

Most zoos strike a balance between these two viewpoints, and ours is no exception.  We feed dry chows, but also feed a variety of fruits and vegetables, meats and fish, eggs and insects and nuts.  A parrot may get all of the nutritional value it feeds from the Zupreem Parrot Maintenance (which looks a lot like Trix cereal), but it can also still peel a section of banana, or crack a Brazil nut with its beak.

In the end, zoo animal nutrition has at least one thing in common with human nutrition - it's a balancing act.  We'll probably never agree on what is 100% the healthiest possible diet.  We just have to look at health, behavior, and other clues to see how we can do they best that we can.