It was a dramatic demonstration when former Primate Center technician Jennifer Campbell mounded two piles of lemur food -- one large, one much smaller -- on a table a few years ago. Her point: The center had been unknowingly overfeeding its animals.
The larger pile of pounds of food pellets, cabbage and bananas represented a human-sized extrapolation of what the generous technicians had been giving the lemurs -- the equivalent of a pile of Big Macs and fries. And the smaller pile represented the human version of a more reasonably sized diet. Since then, the technicians have monitored more closely the portions they give the lemurs.
And since then, Campbell has gone on to earn a Ph.D. from North Carolina State University by conducting landmark studies of lemur nutrition that are sure to influence the health and reproduction of some of the world's most endangered primates.
Her work has included "adventures" ranging from rising at dawn to collect samples of warm lemur feces, to X-raying lemurs to follow the course of food through their guts.
Formerly a zookeeper and naturalist who worked with elephants, tigers, caribou, moose and whales, Campbell came to the center in 1991 as a technician.
"I instantly got interested in the sifakas -- the leaf eaters -- and started tackling some diet issues they had," recalled Campbell. Sifakas are the amazingly acrobatic lemurs that are among the most popular with visitors, and Campbell's first job was to slim down one fatty named Sabina.
"Since she lived with other sifakas, we put a collar on her that gave her access only to certain "diet" feeding stations, and she ended up losing a lot of weight," said Campbell. "And she actually became reproductively active and started to show other, more normal sifaka behaviors. What we learned from Sabina helped us understand how to better feed all of the sifakas."
Extensive dietary knowledge is crucial to success, not just in maintaining lemurs, but for all captive animals, emphasized Campbell. "The hallmark of keeping an animal healthy and surviving in captivity is to feed it an appropriate diet," she said. "If you don't feed them right they're going to be more susceptible to illness, and they're going to have reproductive problems." And captive maintenance has become critical to zoos, she said.
"It used to be that when a zoo wanted to replenish its collection, it would just go capture more animals and bring them back. But that doesn't happen anymore. So, successful captive breeding is very important, and it is dependent upon diet."
The challenge at the Primate Center -- as with other animal facilities -- is that the animals don't know what's best for them," said Campbell. "When you give animals a variety of foods, just like humans they eat the ones that they like the best, and not necessarily the ones that are the best for them," she said. Unfortunately, said Campbell, nutritional knowledge of most animals -- not just the rare ones such as Duke's lemurs -- is sorely lacking.
"Once you get past cattle, pigs, poultry, horses, dogs and cats, there's just this big no-man's-land of animal nutrition," said Campbell. "We can make a lot of guesses and assumptions based on what they're eating in the wild, even though we can't really quantify the amounts of certain nutrients they're consuming."
Duke's lemurs are a classic example of such challenges, since the different species may be as different in their dietary requirements as cows are from dogs. Various lemur species eat diets as diverse as leaves, fruits, insects, seeds and nuts, she said. One lemur even eats bamboo containing enough natural cyanide to kill a full-grown human.
After a trip to Madagascar in 1993, in which she helped care for newly captured sifakas, Campbell decided to do something about the gaps in knowledge of lemur nutrition. Two of the animals died, one from a too-high level of dietary vitamin D, before the scientists developed the proper diet that enabled the third, named Romeo, to survive and thrive. Conversely, said Campbell, the center's goblin-like aye ayes had problems with vitamin D deficiency.
"That just really fascinated me that here was one group of animals that was getting too much vitamin D, and this other group that wasn't getting enough, and they were both lemurs."
Persuading N.C. State nutrition professor Joan Eisemann to take her as a graduate student, Campbell launched her lemur nutrition studies. Classes at NC State provided Campbell with the necessary background in nutritional science and research, while connections at the Primate Center were essential to her work, she said. With the help and cooperation of Cathy Williams, the center's staff veterinarian and Kelly Glenn, veterinary technician, as well as technician staff members who care for the animals daily, she accomplished a number of nutritional studies.
In one study, she dissected animals that had died of old age or natural causes, to produce perhaps the most thorough description yet of lemur gastrointestinal anatomy. With information on this study, she decided to focus on the differences in how the different lemur species process dietary fiber. While some lemurs are fruit-eaters, others subsist on leaves, and still others eat a mix of vegetation.
Thus, she found herself rising before dawn to enter the animals' cages, waiting for them to wake, stretch and defecate. Collecting the fresh feces was critical so that their natural fiber-digesting microbes would still be viable. Campbell took the samples back to her laboratory and analyzed the microbes -- gaining important clues to how the animals digested fiber.
In yet other digestion studies, Campbell fed different lemur species different types of fiber and compared the fibers' digestibility.
And, in perhaps the most exotic experiment, Campbell and the center veterinary fed lemurs small amounts of polyethylene spheres infused with barium, and took periodic X-rays of their guts to follow the course of their digestion.
The results of all this "basic nuts-and-bolts nutrition information" was not only the awarding of a Ph.D. to Campbell this spring. The center is also using the information to improve its animals' diets. However, emphasizes Campbell, these studies represent only the beginning of nutritional studies for these exotic animals
"Now, we know a little bit about their dietary efficiency and how they process fiber," she said. "We don't know a lot about their vitamin or mineral requirements, or the optimum levels of dietary protein."
Campbell said she would like to continue such studies as a zoo nutritionist, helping all her animal charges to lead healthier lives in captivity.
"Before I started this kind of work, I knew I loved animals, but I didn't realize I loved working with all animals," she said. "So on my first job, I walked into the elephant barn, which was full of elephant manure, and basically I just fell in love."