When an animal dies in a zoo or an aquarium in this era of animal rights activism, the emotional outburst that follows often masks the glaring reality of how little science actually knows about the animal world.
The Feb. 24 death of a young, male Pacific white-sided dolphin at the Shedd Aquarium set off a predictable series of events.
A day after the death, dozens of angry pickets from several area animal rights groups surrounded Shedd with banners and signs. They protested that it is cruel to capture and keep wild animals, charging that the 5-year-old dolphin would still be alive had he not been snatched from the Pacific Ocean in 1993.
Grieving over the abrupt and so far inexplicable loss of a highly intelligent, cherished animal, one to which many trainers felt emotionally bonded, Shedd officials couldn’t offer many answers.
A preliminary animal autopsy, called a “necropsy,” gave no clue as to how or why the dolphin died. A series of sophisticated, time-consuming tests on tissues from its vital organs over the next few weeks may or may not divulge a cause of death.
“There’s a great misunderstanding about what we know about the animal world in general,” said Dr. Brian Joseph, a staff veterinarian at the Minnesota Zoo. “People believe science has this huge body of knowledge, when, in reality, we know very little about the life history of most animals in the world.
“If you take an animal like a Pacific white-sided dolphin, we’ve had about 80 of them in all of history to work with and care for in captivity, probably 35 of them since 1980. What little we do know comes almost entirely from captive studies.
“There have been next to no studies done on the white-sided dolphins in nature, so we know virtually nothing about their natural lives in the wild. We hear animal rights people say they live longer in the wild than in captivity, but nobody has that information on how long they live. It’s a very unknown species.”
It is difficult, but possible, for land-based humans to study and record the natural lifespan of individual land animals, such as gorillas and elephants. With marine mammals like dolphins and whales, which range far and wide in their underwater world, it is physically and technologically impossible.
Perhaps the closest any scientist has come to studying individual wild dolphins is Randy Wells, a marine biologist working for Brookfield Zoo. For 25 years he has been studying bottle-nosed dolphins that reside year-round in shallow coastal water off Sarasota, Fla.
Recent studies show that wild and captive dolphins and whales have roughly the same life expectancies, Wells said, though what kills them may differ dramatically. This further complicates any conclusions about whether the Shedd dolphin would have lived longer here or in the sea.
Because they are often so rare and exotic, zoo and aquarium animals are often at least as intriguing after they die to scientists as they are when they are alive.
“There is a saying in the zoo world,” said Dr. Robyn Barbiers, a Lincoln Park Zoo staff veterinarian, “that goes: Even after death, our animals keep on giving.”
The three major institutions here, Shedd and the Lincoln Park and Brookfield Zoos, make up what is known as the Zoological Pathology Program at Loyola University Medical Center in Maywood. When a zoo or aquarium animal dies, University of Illinois veterinary school pathologists and researchers conduct the necropsy on the carcass at Loyola.
“The pathology program has been wonderful for us, allowing us to characterize disease and mortality issues that may occur in our collection,” said Jeff Boehm, Shedd’s director of research and veterinary services.
“Some of our species are evaluated with a `herd health’ technique, used by ranchers who follow health trends in their herds by testing a few individuals. We might have 100 individuals of a certain fish species, and if two or three die, we can use those individuals to look at the health of the general population.
“With our big marine mammals, like the dolphin or our whales, when they die, the primary concern is to find cause of death through an exhaustive schedule of tests.”
Establishing the cause of death, just as it can happen with humans, sometimes can save the lives of other animals in a collection. It might reveal a dangerous bacteria or virus, allowing keepers to take action to protect other animals, for example.
It might also reveal a hidden injury caused by another animal, alerting keepers to watch for hostile behavior, or a nutritional or dietary problem might emerge. Or, as in the case of two beluga whales that died at Shedd in 1992 after being dosed with a deworming medicine, it might painfully announce that a medicine used safely with one cetacean group is fatal to another.
Dr. Michael Hutchins, director of conservation and science for the American Zoo and Aquarium Association, argued that such post mortem studies on captive animals end up benefiting wild populations.
“We’ve learned a lot about diagnosis and treatment of some wildlife diseases from captive animals,” said Hutchins, “that we sometimes can directly apply to wild populations.
“We have a marine mammal stranding network, for example, where we bring in sick animals that have beached themselves. We can treat them and bring them back to health before releasing them back into the wild. We’ve sent zoo veterinarians to Rwanda, where they’ve treated mountain gorillas in the wild for injuries and disease, using techniques developed on zoo populations.”
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Wild animals are killed by predators and die from diseases that are easily treatable in captivity but fatal in the wild. Captive animals, safe from predators, might die from food contaminants they would not encounter in the wild, or from husbandry accidents.
After wild and captive bottle-nosed dolphins die, Wells determines their age by cutting open their teeth, counting rings just as people age trees. He has found bottle-nosed dolphins that have lived into their 50s, though that is a rare experience.
With no such data for white-sided dolphins, sometimes scientists speculate that their life histories are somewhat similar to the bottle-nosed variety. But, said Brian Joseph, knowing that a few can live to be 50 doesn’t really explain about the natural life of bottle-nosed dolphins, let alone any other species.
“If you look at human life as a bell curve, on the far end you’ll find a few people make it to 105 years old,” he said. “You certainly wouldn’t say that human life expectancy is 105 years. If you’ve ever visited Cook County Hospital, you’ll know that a disturbing number of humans don’t even make it to 1 year old.”
Even after a necropsy has been completed, the carcass of an animal often is used for other scientific and regulatory endeavors, said Barbiers of Lincoln Park Zoo.
“The actual carcass or part of it may be sent to the United States Department of Interior forensics department,” she said. “They like to do DNA testing on such things as rhino horn, so that they can prove that smuggled material coming into the country actually is rhino horn, for example.”
Zoos and aquariums that have endangered species in their collections keep detailed genealogical and medical histories of each animal. That information is made available to all institutions working with those species. When one dies, tissue samples from vital organs are deep-frozen and sent around the world to scientists specializing in those species.
“Often we recover sperm from males that die,” Barbiers said, “with the hope that someday we will have a technique to implant it and impregnate a female.
“We try to save as many tissue samples as we can of endangered species, so that we can eventually go back in the population for genetic work. We would save more if we had space, but unfortunately `ultra-low’ freezers (maintaining a 60-degree below zero temperature) are big and expensive.”
Tissue samples from the two beluga whales that died at Shedd are stored at the University of Chicago.
“There are tissue banks for many animals,” said Boehm, “awaiting technological advances that will allow us to do retroactive studies on the animals many years after their death.”
Eventually, he said, tissues from the young dolphin will be offered to various institutions, as well.