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Relative Scarcity: Apes on the Edge

Population Action International (PAI)


A recent study reveals an alarming decline in great ape populations:

  • mountain gorillas and Sumatran orangutans number a few thousand
  • other populations are a fraction of what they were 50 years ago
  • without tougher protection, most species will be extinct in 50 years

February 2000

The Rwanda Mountain Gorilla is critically endangered. Creative Commons: youngrobv

Note: Because some of the information in this article may be outdated, it has been archived.

While our own population is growing steadily, those of our closest biological relatives, the great apes — the non-human members of the family Hominidae — have slid precariously toward extinction. Over the past half-century:

Populations of most of the great apes are 50% less than they were 50 years ago.
  • The population numbers of three out of our four closest relatives — chimpanzees, bonobos and gorillas — have declined by at least half, earning these species an endangered status from the International Union for Conservation of Nature and Natural Resources (IUCN).1
  • The orangutan’s population has slipped between 20 percent and 50 percent over a similar period. Considered vulnerable to extinction in IUCN’s 1996 appraisal, the orangutan is now even worse off — possibly down to half its 1996 numbers — following the past two particularly destructive years of forest fires on the islands of Borneo and Sumatra, and the economic crisis and political unrest that continue to plague Indonesia.10

Population and status of the great apes, 1999

Population sizes of the various species of great apes are tiny fractions of our own.

The decline of bonobos, orangutans, and gorillas is dramatic.
  • Even the most abundant species, the chimpanzee, now numbers well below 200,000 in the wild.6 In the United States alone there are 78 cities with populations greater than that figure.2
  • The other three great apes — the bonobo (a genetically distinct species formerly known as the pygmy chimpanzee), the orangutan and the gorilla — are even less numerous. No more than a few tens of thousands of individuals exist, about the equivalent of human population in a medium-sized town. In fact, the number of human beings born each day — some 350,000 — is greater than the current populations of all other great apes combined.

Species, Scientific Name

Population Size

Degree of Threat

subspecies, scientific name

(~ = approx.)

Pan paniscus

10,000 - 25,0008


Some subspecies of chimps are doing worse and are less stable than others.

Pan troglodytes

100,000 - 150,000
(~2,500 in captivity)


eastern chimpanzee Pan troglodytes schweinfurthi

More than 5,000 in the Democratic Republic of Congo


~8,000 in Uganda, Rwanda, Burundi and Tanzania6


central chimpanzee Pan troglodytes troglodytes

~80,000, chiefly in Gabon and Congo. Parts of habitat still not surveyed.6


western chimpanzee Pan troglodytes verus

No more than 12,0006


The mountain gorilla is in extreme danger of extinction.

Gorilla Gorilla gorilla

40,000 - 65,000


mountain gorilla Gorilla gorilla beringei


Critically Endangered

Grauer’s gorilla Gorilla gorilla grauerii

~17,000 (8,600 - 25,500)8


western lowland gorilla Gorilla gorilla gorilla

30,000 - 40,0007


The population of Sumatran orangutans is critically low.

Homo Sapiens

~6.0 billion

Not Threatened

*estimated before 1997-98 fires; present pop. could be from 25,0009 to as low as 15,00010

Sumatran orangutan Pongo pygmaeus abelii


(subspecies not evaluated)

Borneo orangutan Pongo pygmaeus pygmaeus


(subspecies not evaluated)

Humans continue their overpopulation explosion throughout the world.

Pongo pygmaeus



*estimated before 1997-98 fires; present pop. could be from 25,0009 to as low as 15,00010

Sumatran orangutan Pongo pygmaeus abelii


(subspecies not evaluated)

Borneo orangutan Pongo pygmaeus pygmaeus


(subspecies not evaluated)

Learning from our relatives

Humans are the major threat to the survival of great apes.
Continued killing of great apes for meat could eliminate most of the species.

Much of what science has learned about human physiology and behavior comes from observations of primates, particularly of the apes. This is hardly surprising; more than 98 percent of human DNA is identical to that of chimpanzees and bonobos.3 Yet like selfish big brothers in a dysfunctional family, humans are these animals’ greatest threat. Some experts believe that the growing bushmeat trade — the uncontrolled harvesting of wildlife, and the butchering and marketing of their meat — could eliminate all viable populations of African apes within the next 50 years.4 Despite the acute problem of hunting pressure, the clearing of forest may yet prove the ultimate undoing of efforts to save ape species.

Conclusion: Protection of the great apes is crucial.

Today Homo sapiens is the greatest of the great apes. Humans share the greatest responsibility for these species’ demise, and can reap the greatest benefits for conserving them. But unless we fully understand this greatness, a day may come when — beyond the walls of zoological parks and laboratories — we are the only living member of our Hominid family. Editor’s Note: The bushmeat trade is the greatest threat facing great apes. According to Peter Walsh of the Wildlife Conservation Society, “we’re not talking about starving villagers needing meat. This is heavily organized commercial poaching where money is the motivation.”1 A 1998 report, by the Ape Alliance, based on several field studies over a decade, shows that:2

  • bushmeat is a worldwide activity, affecting great apes and other protected species in Asia, South/Central America, and Africa
  • the bushmeat trade is prevalent in Africa, e.g., 5% to 7% of chimpanzee and gorilla populations are killed each year in the Republic of Congo
  • several thousand apes are killed, by some estimates, in west and central Africa
  • one conservationist’s study estimated that 1 metric ton of smoked bushmeat was unloaded every day at a railway station in Cameroon

1) Friend, Tim. 2002. “Warfare on gorillas.” USA Today, July 8.
2) Ape Alliance. 1998. “African Bushmeat Trade — A recipe for extinction.” Available online at

Population Action International (PAI) is dedicated to advancing policies and programs that slow population growth in order to enhance the quality of life for all people. To these ends, PAI seeks to increase global political and financial support for effective population policies and programs grounded in individual rights. Under the guidance of a distinguished and actively involved board, PAI’s staff work in four areas: policy research, population and environment, political affairs, and international advocacy.

Relative Scarcity: Apes on the Edge

The great apes

Links to sites about the great apes, their behavior, and conservation.

Red list of threatened species

The IUCN publishes an online list and information about threatened species.

Revised Great Apes family tree

In this scheme, only two families are recognised with all the Great Apes (including humans) placed into the same family.

Bushmeat Crisis Task Force (BCTF)

The BCTF has created a comprehensive series of documents describing key aspects of the bushmeat crisis as part of their goal to raise awareness concerning this important conservation issue.

Great Ape Trust

Great Ape Trust is a scientific research facility in Des Moines, Iowa, dedicated to understanding the origins and future of culture, language, tools and intelligence, and to the preservation of endangered great apes in their natural habitats.

Bushmeat project

Stop the slaughter of great apes and ensure their survival. Click on “Bushmeat Action” to find out how you can help.

Be a part of the solution

Population Action International offers several ways in which you can get involved in population-related issues.

Ape Alliance

Select your interest in events, travel, volunteering, or fundraising and click on the world map to find out how you can help in your region to protect great apes throughout the world.

International Primate Protection League (IPPL)

You can support the IPPL or scroll through the extensive list of sites of other like-minded organizations to find the one that best suits your involvement interests. original lesson

This lesson has been written by a science educator to specifically accompany the above article. It includes article content and extension questions, as well as activity handouts for different grade levels.

Lesson Title: Great Apes: Getting to Know the Family
Levels: middle school - high school
Summary: This lesson examines population distribution, habitat, and other aspects of the various great apes. Students can produce a “save the apes” campaign, map the distribution of great apes, create a computer simulation for an ideal ecosystem for an ape species… and more!

Download/view lesson. (To open the lesson’s PDF file, you need Adobe Acrobat Reader free software.)

Useful links for student research

In addition to the links in the “learn more” section above:

  1. IUCN Red List of Threatened Animals (Gland: IUCN, 1996).
  2. UN Statistics Division, “Demographic Yearbook” (New York: United Nations, 1998).
  3. M.C. King and A.C. Wilson, Science 188 (1975): 107-116.
  4. A.L. Rose, African Primates, Winter (1998); G. Streiker, “Poachers Killing Gorillas, Chimps for Bush Meat Delicacy: Activists Blame Logging Companies for Problem,” CNN Interactive, Dec. 30, 1998.
  5. F. de Waal and F. Lanting, Bonobo: the Forgotten Ape (Berkeley: Univ. of California Press, 1997), p. 172.
  6. J. F. Oates, “African Primates,” Status Survey and Conservation Action Plan (Gland: IUCN/SSC Primate Specialist Group, 1996).
  7. S. Saunter, World Conservation Society, personal communications, May 1998.
  8. J.S. Hall and others, Oryx 32, 2 (1998): 122-130.
  9. C. Yeager, Conservation International, personal communications, May 1999.
  10. G. Streiker, “Asian Economic Crisis Could Spell End for Orangutans,” CNN Interactive, March 5, 1999.
  11. H.D. Rijksen and others, Our Vanishing Relative? The Status of Wild Orangutans at the Close of the Twentieth Century (Wageningen: Tropenbos, 1998); C.P. van Schaik, Duke Univ., personal communications, May 1998.


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