Smithsonian National Zoological Park l Friends of the National Zoo



An Apple A Day

The Smithsonian’s National Zoo is one of the few zoos across the country that has a dedicated nutrition department and an enormous comissary to feed all of its animals at Rock Creek and Front Royal.

by Brittany Grayson

Nikki, an Andean bear, (Tremarctos ornatus, also known as the spectacled bear) wakes up every morning around 9 a.m. He lumbers to his feet. He’s not a small bear, at approximately 340 pounds, but he’s an active one. His keepers open his door to let him out into his enclosure where, it seems, someone has left goodies spread all over the yard. He finds an apple behind a rock and munches it thoughtfully as he begins his day at the Smithsonian’s National Zoo.

In the wild, Nikki would be foraging through the Andean forest for berries, bulbs, and bromeliads, and he might spend a significant portion of his day hunting for food—stripping bushes, digging, and walking miles to find what he needs to stay alive and healthy. Being a zoo-dwelling bear, Nikki doesn’t have to worry about what he eats. He has a team of people, from keepers to vets to nutritionists, who determine the best diet for him.

Andean (spectacled) bear
Nikki is an Andean, or spectacled, bear. He lost a whopping 150 pounds, which is his healthiest weight. (Mehgan Murphy/NZP)

The National Zoo is one of the few zoos across the country that has a dedicated nutrition department, which includes two full-time animal nutritionists, a commissary manager, a food specialist, and a staff of nine full-time animal keepers, and an enormous centralized commissary that feeds all of the animals at the Zoo.

Karen Lisi, one of the Zoo’s animal nutritionists, is just one of the people on the front lines who worry about what Nikki does (and doesn’t) eat. Lisi is responsible for making sure that all the animals at the Zoo eat properly, which is quite a challenge, since the Zoo is home to thousands of animals belonging to more than 400 species.

The Zoo’s nutritionists have extensive backgrounds in animal nutrition, but scientists don’t know a lot about the diets of most wild animals. Humans have raised and fed domesticated animals, such as poultry, cattle, horses, dogs, and cats for hundreds of years, though, and Lisi views this knowledge as a good starting point. Many of the animals at the Zoo aren’t well studied, and there are large gaps in our knowledge of what they eat in the wild.

Even in cases where scientists do know what an animal eats in the wild, it’s almost impossible to replicate that diet in a Zoo setting, either because of logistics or because the nutrients in fruits and vegetables vary depending on the climate and soil where they grow. Instead, nutritionists focus on ensuring that animals get all the nutrients they need. They can tell an astonishing amount about what an animal should eat from the anatomy of its gastrointestinal (GI) tract.

“If I know the GI tract of an animal, it really doesn’t matter if it’s covered with scales or fur or feathers. In general I can figure out what to feed it,” Lisi explains. “The important information about the feathers, scales, or fur is the animal’s energy requirements. Birds, reptiles, and mammals have very different metabolic rates. The GI tract may tell me what to feed it, but I also need to figure out how much to feed it.”

The nutrient and calorie content of each diet isn’t just a guess. Lisi uses elaborate mathematical equations to balance out nutrient loads, stomach capacity, and metabolism of the animals to figure out what they need. “You have to enjoy math to enjoy all the equations that go into figuring out nutrient requirements for animals.”

The First Zoo Nutrition Lab in the U.S.

Deb Grupenhoff
Deb Grupenhoff prepares fruits and vegetables for animals at the Zoo. (Jessie Cohen/NZP)

The National Zoo built the country’s first zoo nutrition lab back in 1980, and it’s still a rare feature at zoos today; in fact there are fewer than five nutrition labs at U.S. zoos. Our lab is stocked with ovens for drying samples, centrifuges for separating out ingredients, and a myriad of devices that not only tell scientists what the fat, protein, or carbohydrate content of any food is, but can also determine the amounts of all the useful vitamins and minerals.

This lab, led by Michael Jakubasz, nutrition lab manager, is also well equipped for scientists from the Zoo and from other institutions all over the world to study what animals eat in captivity and in the wild. Currently, Zoo scientists are carefully studying the diets of two dusky titi monkeys (Callicebus moloch) and a two-toed sloth (Choloepus didactylus). They meticulously measure what and how much each animal eats, and then analyze its feces to see how much of it the animal has absorbed. Detailed knowledge like this is rare for even zoo species, and it’s extremely valuable. Scientists share this knowledge throughout the zoo and the scientific community, so that every day, animal care experts know a little bit more about the world than they did the day before.

Creating the Perfect Diet

The nutritionists use all this knowledge to create a diet for each animal in the park. They detail exactly what each animal should eat, in precise quantities on diet sheets.

“They’re almost recipe sheets,” Lisi explains. “They’re very straightforward. Of course, the diets are constantly changing as animals come into the collection, are moved around, we have a birth, or there is a change in health status.”

As a Zoo nutritionist, Lisi is works with dozens of people to implement and monitor the diets of each animal. This collaborative effort includes the veterinary staff and the animal keepers.

This precise formula becomes very important when animal care staff are trying to change an animal’s weight. Take Nikki, for instance. When he came to the Zoo, he was accustomed to eating all sorts of sweets, and he was grossly overweight. Keepers and vets work together to determine an animal’s body condition. With Nikki, they had a hard time feeling their way through the fat to even find his bones. But, just like humans, animals can’t lose weight too rapidly, so Lisi worked with the vets and keepers to lay out a very slow, but steady, weight loss plan for him. They set a target weight based on historical records of what a male Andean bear should weigh. As they slowly inched his weight downward, everyone kept a close eye on how he looked and how he behaved. As he lost weight, he became more active, climbing over the trees and logs in his yard and acting much like an Andean bear would in the wild.

It took more than a year, but Nikki lost a whopping 150 pounds and is finally at what the vets and nutritionists deem his healthiest weight. In fact, Nikki is now too active. He didn’t put on as much weight as his keepers would have liked during winter months, and so Lisi had to experiment with his diet, adding different items and amounts, until he was brought to a weight everyone was comfortable with.

The nutritionists, the keepers, and the vet staff do this sort of juggling all the time with each of the animals at the Zoo. “I’m probably changing something in the diet prep books at least daily and often several times a day,” Lisi says. “There’s a lot of maintenance work to make sure the food is what it’s supposed to be and to make sure it’s in the right place at the right time.”

The Commissary

The logistics are handled by a commissary manager, a food specialist, an administrative assistant, and a team of keepers dedicated to feeding the animals. They’re housed in an enormous facility most Zoo visitors don’t even know is there. Stretched under parking lot C is the building that comprises the Zoo’s commissary. This is where all the food for the animals is received, stored, and prepared.

This gargantuan facility is as clean and organized as the kitchen in any human restaurant, and operates the same way. Many of the keepers even have cooking or restaurant experience. Deb Grupenhoff, the food specialist at the commissary, used to manage a restaurant for humans.

“We have the same food safety as you’d find in a restaurant. We have the same worries about temperature, sanitation and knives, and keeping meat separate from the veggies,” she explains.

Of course, their jobs not only include the sanitary preparation of diets for over three-quarters of the Zoo’s residents, but also for acquiring the more than one ton of woody browse (the woody material, including bamboo, provided to the animals in the park) and bamboo required for the herbivores of the park weekly (1,400 pounds of which is for pandas alone). The daily harvest of browse and bamboo is a concrete reminder that the Department of Nutrition is responsible for every aspect of feeding and nutrition for the animals at the Zoo (see sidebar “75,000 Pounds of Bamboo” ).

Enough Food For Three Months

Tyrone Savoy
Tyrone Savoy weighs and measures diets for the primates.(Jessie Cohen/NZP)

The Zoo’s commissary is much larger than almost any human restaurant, and according to Mike Maslanka, senior nutritionist and head of the Nutrition Department, there is enough food stored in the commissary to feed the entire Zoo animal population for at least three months.

“Everyone might not be happy with what they get,” he explains, referring to the animals as well as the keepers, and stressing that the animals wouldn’t get all the food variety they’re used to. “Some animals might gain weight and some might lose weight. But we’d be able to keep them all alive.”

This cache of food protects the Zoo against any sort of meteorological or political crisis that might prevent food deliveries from getting to the Zoo. They have an even bigger stash of some foods, though. For instance, Maslanka prefers to order fish once a year. The fish are frozen right after they’re caught and sent immediately to the Zoo. This way they’re fresh, and the Zoo knows that they’ve been frozen and maintained properly.

To house everything, the commissary has two enormous room-size freezers, as well as two even larger refrigerators. A room with humidity control is devoted to ripening bananas. And a room that smells warmly reminiscent of a barn houses all the dry food and biscuits the animals need. The Zoo works with dry food distributors to create just the right kind of food for some animals. But some of it, Grupenhoff explains, like dry dog food for the maned wolves, “We buy off the shelf just like everyone else.”

In addition to all of the stored food in the commissary, the Department of Nutrition also stores more than 450 tons of hay in the barns at its campus in Front Royal, Virginia. This, in itself, may not be noteworthy among zoos, aside from the fact that Maslanka is responsible for managing all of the hay which is produced on the grounds of that facility, located in the western Virginia mountains. “Being able to grow all of our own hay is a great fail-safe in the case of a drought year or several drought years in a row,” he explains.

Sunrise Deliveries

All of this food is carefully prepared into meals, and placed in bins for each individual exhibit. The commissary keepers then place the bins in bigger plastic totes and deliver them to each animal house every morning, 365 days a year. The keepers start early, often before the sun is up, so that they can be sure the animal keepers have the food when they need it.

In the pre-dawn dark, commissary keepers drive a small fleet of trucks and carts, and drop off totes at each animal house. This includes fresh food, but may also include hay from the hay barn (which some animals, such as elephants and cattle, eat, and others, such as gorillas and orangutans, use as bedding), live fish and worms, and browse. The staff clears away the old totes, and takes them back to the kitchen to be cleaned for use the next day. As soon as the keepers get back, they start all over again—preparing diets for the day, and the one after that.

As keeper Sharyn Hood explains, “Regardless of what happens, everyone has to get fed. We do as much as we can get done in one day. And when we have free time, we start on the work for tomorrow. The pandas don’t take a holiday on July 4th. They still want to eat.”


BRITTANY GRAYSON is a web content editor and science writer for Friends of the National Zoo.


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Smithsonian Zoogoer 38(6) 2009. Copyright 2009 Friends of the National Zoo. All rights reserved.