Death and dying (zoology)

The life span of all species in the animal kingdom depends upon genetic composition, environmental conditions, and the amount of energy expended throughout their lifetime. The natural lifespan varies from one species to another. Insects generally have the shortest lives. The adult mayfly lives only a few hours, while the fruit fly lives for thirty to fifty days. At the other extreme, the giant tortoise may live up to 177 years, the Greenland shark up to 500 years, and the quahog clam can live over 400 years. Human life expectancy has increased substantially since the beginning of the twentieth century. In 1998, it ranged from seventy-five to eighty years in the United States, Canada, Western Europe, and Australia, compared to fifty-five years in most of Africa. By the early 2020s, the average lifespan in Western developed nations rose to between seventy-seven and eighty-three years, and the average lifespan in African nations was sixty-three years.

Environmental conditions affecting the genetically determined life span and hastening death include the number and ferocity of predators, viral, bacterial, and fungal diseases, poisons and pollutants, changing climate, and the rise of carbon dioxide in the air. Humans have contributed to the annihilation of many species and placed others close to extinction by either deliberately or accidentally destroying animal habitats and over-hunting wildlife. For example, the Pinta Island tortoise was declared extinct in 2015, Hawaii’s poʻouli bird was declared extinct in 2019, and Australia’s Mountain mist frog was declared extinct in 2021. In 1973, the United States Congress passed the Endangered Species Act to protect endangered animals and their habitats. The Environmental Protection Agency (EPA) monitors the fate of endangered species. If pesticide use adversely affects the habitat of an endangered species, the EPA can prohibit it.

Pollutants

Maritime oil spills, which kill huge numbers of marine life and birds, affect wildlife species differently. Birds, especially, are sensitive internally and externally to the effects of crude oil and its refined products. If they become coated with oil and their feathers collapse and mat, the insulating properties of their feathers and down change, making them vulnerable to hypothermia. They become vulnerable to predators and can suffer from dehydration, drowning, and starvation.

Cetaceans, sirenians, and pinnipeds, who depend on air and have amphibious habits, are all susceptible to the effects of oil spills. Like birds, they can suffer from hypothermia. Due to ingesting the oil during grooming and feeding, they suffer from organ dysfunction, congested airways, damaged lungs, gastrointestinal ulceration and hemorrhaging, and eye and skin lesions. Sea turtles are particularly vulnerable during their breeding season, as their nesting sites are on beaches, and their eggs may become contaminated by the oil. Newly hatched turtles must move over the oiled beach to the water. Among the most deadly oil spills was the wreck in Alaska of the supertanker Exxon Valdez in March 1989, which resulted in more than thirty thousand seabirds dying. In April 2010, the largest oil spill in history occurred when the Deepwater Horizon exploded off the coast of the southern United States, devastating the surrounding aquaculture.

Persistent organic pollutants (POPs) have been related to many behavioral problems in birds, marine mammals, and fish, as well as in humans. Studies of humans exposed through food to POPs show a possible relationship to disruptions of the immune system. This finding has been used to explain why more seals and whales are dying and getting stranded. High levels of cancers in fish have been attributed to another class of potential POPs. Environment Canada reported that when POP levels were reduced, population declines in some birds reversed.

Viral and Bacterial Disease

Nonhuman animals, like humans, are vulnerable to viruses. Livestock contract highly contagious and serious diseases. Among the more commonly known are foot and mouth disease, which affects hoofed animals; scrapie, which affects sheep; and bovine spongiform encephalopathy (BSE), also known as mad cow disease, which occurs in cattle. BSE appears to jump species; humans who contract BSE can develop Creutzfeldt-Jacob disease, a fatal brain disorder. Pigs contract swine fever. Capripox occurs in sheep. In Africa, Rift Valley Fever kills livestock and humans. Poultry can contract avian influenza and Newcastle disease, both of which spread rapidly, killing more than 90 percent of infected birds. Other diseases include Enterocytozoon hepatopenaei, which threatens shrimp farms in Asia, Camel pox, which kills around 25 percent of the young camels it infects, and African swine fever, which is highly contagious with nearly a 100 percent mortality rate.

Because rabies is fatal in animals and humans, many countries require a quarantine period for animals entering the country. In wildlife, trapping has been used to prevent the spread of rabies. However, usually, the healthier animals are caught in traps and not the sick, who are less active, symptomatic, and debilitated and are more likely to deviate from their normal behavior.

Organized Animal Fighting, Animal Farming, and Sport Hunting

Humans are voracious predators of other species, killing nonhuman animals for food, clothing, sport, scientific experimentation, and financial gain. Animals meet their death through organized fighting: bullfighting in Spain and Mexico and cock fighting in the United States and several Asian cultures, usually resulting in the death of one or both roosters. Dog fighting, although banned in most of the United States, is still held clandestinely.

Animal agriculture is the largest food industry in the United States. Animals reared for slaughter are frequently housed in crowded conditions in large buildings, which are ideal for disease. Under natural conditions, chickens can live for as long as fifteen to twenty years. In a modern egg factory, hens live about a year and a half. Each year in the United States, about two-thirds of the 125 million pigs raised for slaughter live their lives in a confinement system, as do about half of the ten million milking cows and heifers raised. When birds are debeaked, and calves and pigs are weaned prematurely, they can die from the shock. Slaughtering is sometimes undertaken without safeguards in place to prevent unnecessary pain.

About 5 percent of the United States population legally hunts animals. Sport hunting of polar bears in areas of Canada eventually led to such a substantial loss of bears that the local government banned hunting in 2002. In 2001, the government of British Columbia placed a moratorium on the hunting of grizzly bears. The whale population initially decreased because of hunting. The blue whale, which once numbered 200,000, was estimated to be between 10,000 and 25,000 in the 2020s. Marine mammals also become accidentally entangled in fishing nets and collide with boats. Dolphins died at a considerable rate due to tuna fishing methods until US legislation prohibited the method, and the number caught in nets was reduced dramatically. Manatees, who move slowly and sometimes sleep near the water's surface, are particularly vulnerable to being fatally hit by motorboats. They were listed as endangered species under the federal Endangered Species Act until 2017, when they were labeled as threatened.

Poaching remains a significant global problem in the twenty-first century. Elephants are killed for their ivory tusks, tigers for their skins, and rhinos for their horns. Other animals are killed in the activities of the exotic pet trade, such as the parents of young orangutans. The most commonly trafficked mammal, the pangolin, is killed for its scales.

Scientific Experimentation

Using animals in scientific experiments has been widely sanctioned worldwide for testing consumer products, disease prevention or progression techniques, the effects of noxious agents, and psychological theories of behavior. An animal rights movement developed in the late 1970s and early 1980s to protest this use of animals, who not only died during and following the experimental procedures but were also subjected to extreme pain and injury. Industrial manufacturers and scientists were urged to find alternate methods of safety testing and conducting experiments. The Johns Hopkins Center for Alternatives to Animal Testing was founded in 1981, while In Defense of Animals (www.idausa.org) grew out of challenges to the University of California’s research. It grew into one of the foremost animal advocacy organizations in the United States. The ethical question raised by animal rights groups is whether nonhuman animals should be treated as independent sentient beings and not as a means to human ends.

Beyond the ethical issues raised by philosophers, such as Tom Regan and Peter Singer, are the questions concerning the emotional life of animals and whether animals experience grief and have a concept of death. Marc Hauser, an animal-cognition researcher, maintained that animals, lacking a capacity for empathy, sympathy, shame, guilt, and loyalty, are without self-awareness or an awareness of what another of their species experiences and therefore are incapable of having a deep understanding of death.

Researcher Cynthia Moss, at the Amboseli Elephant Research Project in southern Kenya, takes a different view. From her field observations, she maintains that elephants have a concept of death. They recognize one of their own carcasses or skeletons, always react to the body of a dead elephant, and have been seen putting dirt on a dead elephant’s body and covering it with branches and palm fronds. Healthy elephant mothers whose young calves have died look lethargic for many days afterward, trailing behind their families.

Wild and domesticated animals have been documented reacting to losing a mate or companion, which can be interpreted as mourning behavior and grief. They often search for their deceased companion or become despondent and stop eating. This is particularly well-documented in animals whose young offspring dies. Giraffes will stay by the body of a deceased giraffe pup for up to several weeks, primates may carry the dead body for an extended period, and researchers have documented wolves burying their young.

Principal Terms

Cetaceans: plant-eating marine mammals, such as whales, dolphins, and porpoises

Marine Mammals: part of the class of mammals that adapted to life in the sea

Myocarditis: inflammation of the heart muscle

Persistent Organic Pollutants (POPs): chemicals that remain in the environment for a very long time and can be found at long distances from where they are used or released; they are nearly all of human origin

Pinnipeds: flipper-footed marine mammals, such as sea lions, fur seals, true seals, walruses

Sirenians: plant-eating dugongs and manatees

Bibliography

Anderson, James R. “Responses to Death and Dying: Primates and Other Mammals.” Primates, 2020, doi.org/10.1007/s10329-019-00786-1.

“Average Life Expectancy by Country.” Worlddata.info, Aug. 2024, www.worlddata.info/life-expectancy.php. Accessed 10 Sept. 2024.

“Deepwater Horizon – BP Gulf of Mexico Oil Spill.” Environmental Protection Agency, 24 July 2024, www.epa.gov/enforcement/deepwater-horizon-bp-gulf-mexico-oil-spill. Accessed 10 Sept. 2024.

De Waal, Frans B. M. Good Natured: The Origins of Right and Wrong in Humans and Other Animals. Harvard UP, 1996.

Frey, Michelle. "Meet the 7 Longest Living Ocean Animals." Ocean Conservancy, 29 Dec. 2021, oceanconservancy.org/blog/2021/12/29/7-longest-living-ocean-animals. Accessed 20 Sept. 2024.

Gould, James L., and Carol Grant Gould. The Animal Mind. Scientific American Library, 1994.

Hauser, Marc D. Wild Minds: What Animals Really Think. Henry Holt, 2000.

Jaworowski, Chris. “The Role of Trapping in Wildlife Disease.” Outdoor Alabama, 16 July 2017, www.outdooralabama.com/node/1826. Accessed 10 Sept. 2024.

Levine, Herbert M. Animal Rights. Austin, Tex.: Steck-Vaughn, 1998.

Mason, Jim, and Peter Singer. Animal Factories. New York: Harmony Books, 1990.

Moussaieff Masson, Jeffrey, and Susan McCarthy. When Elephants Weep: The Emotional Lives of Animals. New York: Delacorte Press, 1995.

Regan, Tom. The Case for Animal Rights. U of California P, 1983.

Rott, Nathan. “Decline In Hunters Threatens how U.S. Pays For Conservation.” NPR, 20 Mar. 2018, www.npr.org/2018/03/20/593001800/decline-in-hunters-threatens-how-u-s-pays-for-conservation. Accessed 5 July 2023.

Singer, Peter. Writings on an Ethical Life. HarperCollins, 2000.

Taylor, Marianne. The Animal Mind: Profiles of Intelligence and Emotion. Abrams, 2024.