Life at the Zoo

by Phillip T. Robinson

  Wild animals must be competent at disguising their diseases. Don’t humans conceal their weaknesses from bullies for similar reasons? It is an essential skill for survival. Imagine, for example, a sick bird perched on a branch. The odds of being the target of a hawk or cat increase appreciably if it displays external signs of illness. After all, predators, by occupation, must be masters at detecting vulnerability. Animals at the familiar African waterhole are usually aware that predators are surveying the herd for a victim. In fact, there seems to be a tacit understanding—a sort of gentlemen’s agreement—that someone among them will be tonight’s supper for the lions, leopards, and hyenas. To me, this is reminiscent, in our society, of the presence of traffic cops apprehending speeders on a highway. The speeders know they are speeding and that the police are around. The patrol officers know that they are going to give out some speeding citations (they may even have an established quota). There is a safety-in-numbers mindset among the speeders, who hope and expect that it will be someone else, not they, who gets the ticket today—and usually it is. Animals also seem to go about their lives with the notion that they, too, will not be the ones on the menu. The placement of eyes on hoofed animals is no accident. Located more laterally on the head, their field of vision—in some cases more than three hundred degrees—is much greater than for most other species, in order to detect the presence of approaching predators.

  Concealing illness has been conditioned as a survival mechanism through many millennia, and it is a hurdle that zoo veterinarians are always looking for ways around. Undetected animal observations are the purest, most valuable ones of all, and, like Dr. Jane, I also often bribed the great apes with small tokens behind the scenes to curry their trust and cooperation.

  Our human medical counterparts who relate most to zoo veterinarians are newborn specialists and pediatricians. Like zoo veterinarians, they labor under many of the same constraints because their patients cannot talk to them. With relatively few exceptions, however, their patients don’t attack and bite, although I recently saw a recruitment ad for a recreation therapist at a mental hospital in which the job description noted under the conditions of employment that “incumbents may be exposed to residents who may be abusive or combative.” At least human patients, mental and otherwise, have family members to fill in some of the information gaps. I wonder how physicians would feel if they had to practice exclusively on illiterate mimes. After all, isn’t that the case in a zoo?

  The presence and interactions of veterinarians and animal keepers have marked effects on the behavior of the zoo animal patient, and they must be constantly placed in context. Making useful patient observations takes planning and coordination with the animal keepers. One of the worst things a keeper can do is to alter the daily routine before the veterinarian arrives to view a sick animal; the presence of a veterinarian will do that soon enough anyway. Animals are quickly alarmed by changes in the familiar. In their eagerness to help, some keepers will change that routine by not feeding animals or by segregating the patient from others. In some cases it is only because of the trust that animals may have in their keepers that a veterinarian is able to get close enough for meaningful observations at all. The keeper/animal bond may also be vital in encouraging individual animals to consume medications that are essential to their recovery. When anything out of the ordinary happens, many captive animals automatically go into a state of apprehension, simply because familiar activities have ceased.

  Stress, like oxygen, has its pros and cons. We can’t live without it, but too much at the wrong time and place is damaging (it’s called oxidation). Stress is one of the most fundamental biological mechanisms that animals and people have to cope with life challenges. It was scientifically described in 1950 by Dr. Hans Selye, a famous Austrian physiologist in his 1956 book Stress of Life, which initiated a focus for the medical profession on a broad new area of physiological research. In the preface, Selye writes, “No one can live without experiencing some degree of stress all the time. You may think that only serious disease or intensive physical or mental injury can cause stress. This is false. Crossing a busy intersection, exposure to a draft, or even sheer joy are enough to activate the body’s stress-mechanism to some extent. Stress is not even necessarily bad for you; it is also the spice of life, for any emotion, any activity causes stress.”

  This field of research had centered on defining the hormonal and chemical events related to various forms of stress. Selye dubbed this remarkable system of alarm and coping mechanisms the “General Adaptation Syndrome” (also called GAS for short). This complex of biological events has also been called the “fight or flight” mechanism, since, in its more dramatic form, it takes place when an animal or person has either to run from an attacker or stand and fight. The accumulation of stress, both good and bad, can lead to physical disorders to the point of producing “distress.” The negative effects of stress have been widely examined in both people and animals. Recently it was reported that actors who were the recipients of Academy Awards outlive their less honored peers by an average of four years, and those receiving multiple Oscars lived an average of seven years longer. Is less stress from achieving long sought-after recognition and the ensuing sense of inner serenity translated into beneficial physiological events that can extend longevity? Possibly so, if this is any measure.

  Since Selye’s original work, thousands of articles have been published on the subject of stress. Pleasure itself is simply a form of stress, technically speaking. People attempt to modify their behavior and lifestyles to reduce unwanted stress (we all seek the pleasurable kind) through transcendental meditation, Tai Chi, biofeedback, vitamin supplements, special diets, colon-cleansing enemas, sabbaticals, vacations, and Covey day planners. Those same dynamics that allow us to adapt to everyday variations in our environments can also lead to our demise when they are excessive. When we remodel zoo exhibits, alter diets, or add new cagemates, we seldom know for certain whether we are increasing or decreasing distress in animals.

  Selye was able to identify important physical and chemical changes that are life-sparing adaptations. These same mechanisms are essential, for zoo animals and people alike, to survive in an ever-changing world. Without these coping mechanisms, it is doubtful that we could survive for long at all. It goes something like this: An organism is subjected to a stressor—it could be a sound, a sight, an emotion, an infection, or a menacing threat. In response to this challenge, neurological and chemical circuits become activated. The initial event is called the “alarm reaction,” wherein the body’s defense mechanisms are marshaled to meet the challenge of the stimulus. This is followed by the “stage of resistance” in which adaptive mechanisms are brought into full, sustained force. Last, if the stressor does not relent, the third stage takes effect, the so-called stage of exhaustion, resulting in either disease or death.

  It is difficult to overstate the importance of Selye’s work to zoo animal medicine. The concept is not limited to things that scare animals, but also encompasses environmental stresses, such as cold, heat, sound, or improper diet. The success of a species in perfecting the flexibility of its “fight or flight” capabilities is a major factor in survival and evolution. Those animals that are most adaptable are more likely to reproduce and continue their evolutionary pathway. The others go the way of the dinosaurs into the fossil archives.

  Once the GAS is activated, more subtle signs of disease are masked in zoo patients, and we are left with the physical part of the medical exam. Or we can persevere and return at a later time when they have achieved a more normal state. In everyday kinds of stress cycles the body gears up for fight or flight, to one degree or another, and returns to normal when the stressor goes away. Over time, when GAS is in full swing, immune mechanisms become suppressed, increasing susceptibility to infectious and metabolic diseases. In other words, too much stress is bad and can eventually kill you. But people seem to have known this long before Selye documented it. During this GAS process, the
body’s intrinsic steroids are released from the brain and the adrenal glands to serve valuable purposes in carrying our bodies through an acute crisis. We all understand from popular medical news reporting that chronic stress causes ulcers, heart disease, stroke, and death; all are indicators that we have failed to cope fully with our life stressors in the context of our genetic makeup and environment. Some animals seem to cope poorly with captivity because of the limitations of their behavioral and adaptive capacities. Many more fail, however, because we have fallen short of understanding and providing for their unique physical and behavioral requirements. This is the overall preventive objective of an animal health program in zoos—the reduction of unwanted stressors.

  Some animal species seem much less malleable in captivity than others, and zoo veterinarians keep little mental lists such as “Animal Species Not Suited for Captivity.” However, our prejudices can change quickly when someone finally figures out what it takes to keep a particular species consistently happy and alive. The list titled “Zoo Animals That Hardly Ever Get Sick” is one of my shortest, but favorite, ones. I would put hippos first on my list, followed by a few other species, but this would probably vary from zoo to zoo. Rhinos, camels, and crocodiles would also probably be highly ranked.

  Koalas moved off of my “not-suited” list after we finally figured out how to care for them properly, and they are a good case study for the management of a novel species in captivity. A cute, but historically challenging, species to maintain in captivity, they illustrate many points about the nuances of animals’ adaptive capabilities for captive living. The techniques for keeping koalas alive and well were pioneered in several Australian fauna parks, but particularly at Lone Pine Koala Sanctuary in Brisbane. People find koalas to be very charming, perhaps somewhat undeservingly so, given their penchant for sleep and general inactivity; and in many ways they depart from the traditional model of choosing exhibit animals. First, they are largely nocturnal (boring to many people, since zoos often exhibit nocturnal animals in daylight exhibits), and most often they present as a furry lump on a branch, offering visitors a view of their hunched-over backsides. Nonetheless, the teddy-bear mystique and cultural affinity people have for them have put koalas in the class of highly desirable, charismatic exhibit species.

  A second koala management anomaly is their highly specialized diet. Most zoos do not have the food supply to support these obligate eucalyptus-leaf eaters. Fortunately for koalas, their diseases are relatively few, since their nursing care options in illness are more limited than average. Koalas don’t appreciate handling, unless conditioned from an early age, and this contact should start as soon as they leave the pouch. Unconditioned koalas run, climb, bite, scratch, and become stressed. Unlike squirrels, monkeys, and other arboreal mammals, koalas can be readily chased down from a tree if you succeed in putting a pole over their heads with a small banner on it. I once accompanied a koala field research trip with Australian researchers and saw this demonstrated. On the ground, however, wild koalas can run like rabbits when motivated.

  Most koalas did not survive life aboard ships during attempts to take them to zoos outside Australia. But all that has changed with advances in husbandry knowledge and rapid transportation options. If you ever observe a koala drinking water, it most likely has a terminal illness and its hours of remaining life are numbered—after all, koala is an Aborigine word that means “doesn’t drink.” They obtain virtually all of their water from their leafy diet, and they soon dehydrate if they stop eating. The only koala that I’ve ever seen consume water from a bowl was one that I gave steroids in its last few days of life in a last-ditch effort to encourage him to eat.

  The practical solution to keeping captive koalas is their semidomestication. They have an extraordinary capacity for taming if conditioned from the time they emerge from the mother’s pouch, even to the point of tolerating a dog as a mode of transportation. Koalas should be weighed regularly to detect nutritional problems. They also should be examined with experienced hands along their shoulder blades, to identify the loss of muscle mass, which indicates declining health. When trained, koalas will sit on your hand or with their bum at the crook of your elbow, their two hands resting comfortably in yours. They seem to fare best when housed primarily in sheltered cubicles, where their food intake and microenvironment can be closely monitored.

  Once these husbandry measures were implemented in a new koala facility at the San Diego Zoo in the 1970s, the koala population boomed. To assure a bountiful supply of eucalyptus species, their favorite varieties can be readily grown in small plantations in suitable climates. The San Diego Zoo now provides koalas on loan to zoos in snowy latitudes and sends freshly cut eucalyptus boughs via Fed Ex airfreight. Koala medicine is mostly preventive and based on detailed husbandry procedures—a testimony to the fundamental value of this approach in zoo medicine.

  To make the best assessment of their behavior, I have always preferred to view animals when they are unaware of my presence. Binoculars are essential for animal observations in zoo medicine, and video monitoring has become an invaluable tool in special situations in the captive management and reproduction of many species. The San Diego Zoo staff and the world have been able to view giant pandas via the internet on the “Panda Cam” throughout the births and infancies of the two giant panda babies born in 1999 and 2003.

  Young koala jockey and Alsatian at Lone Pine, Australia

  The keeper who knows the normal behavior of animals is the vital link to health clues, breeding, and well-being. Some individuals are masters at reading their animals, while others simply suspect that something is “different” or “abnormal” about their behavior. Mixed exhibits can make observations more difficult, but, if interaction is the norm, these social situations can produce useful information relating to health about animals. My guess is that the future will bring more widespread technology to the monitoring and treatment of animals in zoos, including the selective implantation of telemetry devices that will transmit data on blood pressure, heart rate, blood sugar, adrenal hormones, and other important physiologic factors. The basic electronics are now in development and used in research institutions, and are getting smaller and more versatile. Individuals requiring long-term medications may even be managed with devices that monitor certain physiological parameters related to blood chemistries, cardiac performance, and blood pressure. Perhaps one of the most interesting applications could be the use of implanted drug delivery devices to medicate or sedate an animal gently without the stress of physical handling and tranquilizer darts.

  Before a zoo opens up to the public each day, many animals are acutely conscious of people who are in the public spaces, but they relax when the familiar crowd starts to stir. If you step over a barrier where the public does not normally tread, most animals become alarmed. Great apes are perhaps the most amusing in their interaction with visitors and zoo personnel; they can pick a zoo veterinarian from a crowd of hundreds in front of their exhibit. After viewing animals from a distance, it is usually necessary to move up for a closer look, often when they are closely confined. I have always found this to be uncomfortable, since many animals find it so. They feel a sense of vulnerability and know that your gaze is different than the average observer, and they seem relieved as you depart, as if you were a predator cruising their neighborhood for food. Imagine how you would feel if someone stopped his car, walked into your yard, and stared at you with binoculars as you reclined on your front porch.

  The bush dogs are near the top of a zoo veterinarian’s animals-not-suited-for-captivity list. These small South American wild canines are an example of the zoo animals from hell. Nervous, busy, stressed-out little creatures, they are fond of running in circles. Skin problems, fighting, diarrhea, foot sores, and stereotyped behavior—you name the problem, and the bush dogs have it, again. They keep everyone forever busy with medical issues until their eventual departure to bush dog heaven or another naive zoo. Someone needs to do for bush dog medicin
e and husbandry what Australian fauna parks did for koalas and platypus—figure out what they need. If perseverance counts for anything, I am sure bush dogs are very competent doing what they do in the wild, since nothing will deter them from their chosen task, however self-destructive. For now, and for most zoos, they are still too tightly wound for captivity.

  “I shouldn’t, but I’m going to have the garbage.”

  11. FEEDING THE ARK

  The Nutritional Wisdom of Animals

  The cells of a Komodo dragon, elephant, and hummingbird require essentially the same nutrients for metabolic chemical reactions necessary for growth and maintenance. It is the myriad ways by which nutrients make their way into those body cells that provide many of the challenges and much of the fascination of comparative nutrition. What is food for one animal may be as nutritionally inert as a rock for another. At one extreme, termites eat and digest woody plant materials, whereas most creatures only build their homes and nests with such materials. The ways in which living creatures obtain, mechanically alter, digest, and assimilate foods vary in relationship to the environments within which they evolved.