Great Ape Trust Scientists Dr. Rob Shumaker and Dr. Serge Wich collaborated on a chapter in a book looking at reproductive aging across the primate order.

Menopause isn’t just a human phenomenon

Des Moines, Iowa – September 29, 2008 – Menopause is not just a human phenomenon, but also occurs in other species of primate, according to a new book that includes a chapter written by Great Ape Trust of Iowa scientists Dr. Rob Shumaker and Dr. Serge Wich.

Edited by Dr. Sylvia Atsalis, Susan W. Margulis and Patrick R. Hof, Primate Reproductive Aging: Cross-Taxon Perspectives, is a volume in a series of books on interdisciplinary topics in gerontology published by Swiss publisher S. Karger AG.

Atsalis and Magulis, both of whom are affiliated with the Lincoln Park Zoo in Chicago, were the first to document menopause among female gorillas. In a nationwide zoo-based study, they evaluated the progestogen levels in 30 females, 22 of whom were geriatric. One-third of them showed variable hormone patterns suggestive of perimenopause. Atsalis and Magulis reported that follow-up data on 10 of the perimenopausal females indicated that subjects experienced age-related changes in reproductive functions that mirrored those in humans.

Their findings, and those of experts of other primate groups who were invited to write chapters for the book, run counter to the claims of some evolutionary anthropologists and biologists, who believe that a lengthy post-reproductive lifespan is a uniquely human attribute.

“Experiencing menopause was thought to be an enormous distinction among humans, and this calls all of that into question,” said Shumaker, who along with Wich authored the chapter on orangutans with Lori Perkins, chair of the Orangutan Species Survival Plan and director of animal programs at Zoo Atlanta.

Dr. Rob Shumaker

In their chapter, the three scientists noted that birth rates do not decrease with age among wild female orangutans, but captive female orangutans do have an appreciable post-reproductive life span. Both in the wild and in captivity, females live to about 53 years – a finding that discounts a widely held assumption that captive females live longer than their counterparts in the wild. The chapter by Shumaker, Wich and Perkins reveals that wild female orangutans begin reproducing at a mean age of 15.4 years and have a mean birth interval of 9.3 years.

In the past, it was thought that captive female orangutans should begin reproducing at much younger ages. The two orangutan experts at Great Ape Trust said the new information promotes captive management practices that are much more consistent with orangutan behavior and reproduction in the wild.

The authors note that the age of 40 was previously considered to be “old” for an orangutan, and husbandry and management may have been such that it was considered risky to allow reproduction among females thought to be nearing the end of their lives. The question of menopause in orangutans is still under investigation.

“This information helps us tremendously in terms of the decisions we make about orangutans in captivity,” Shumaker said. “Young orangutans need to be with their mothers for the better part of a decade, at least for six or seven years.”

Dr. Serge Wich

In addition to updating and correcting misconceptions about orangutan reproduction, the chapter emphasizes data on reproduction collected from wild and captive populations of orangutans. “It’s very rare for this kind of collaboration to be happening, particularly with orangutans,” Shumaker said. “I am very, very proud of that, and it begins what I hope will be a number of publications that will expand our knowledge about orangutans.”

Great Ape Trust’s strength in such collaborations comes from its support of international ape conservation initiatives such as the Ketambe Research Center in Sumatra, where Wich has been research co-manager since 1997. Ketambe is one of the longest-running orangutan field study sites in the world, with longitudinal data dating back to 1971.

In the wild, female orangutans have the slowest rate of reproduction of any terrestrial mammals, giving birth every seven to nine years – a distinction that makes them both unique and vulnerable, Shumaker said. Long intervals between orangutan births coupled with habitat loss increase the severity of the threat to the red apes, found only on the islands of Sumatra and Borneo.

All populations of wild orangutans are endangered. “Habitat destruction, habitat conversion – particularly for agriculture – and poaching are major concerns,” Shumaker said. “These can have significant impacts on prospects for long-term survival.”

Wich added that although the situation for orangutans in the wild is dire, there are still opportunities to save this species along with the forests that are essential to them and to the people living nearby.

The book also includes data on lemurs, marmosets, tamarins, cedibae, rhesus macaques, Asian colobines, chimpanzees and humans.

Wild female orangutans begin reproducing at a mean age of 15.4 years and have a mean birth interval of 9.3 years.

BACKGROUND INFORMATION

Great Ape Trust of Iowa is a scientific research facility in Des Moines dedicated to understanding the origins and future of culture, language, tools and intelligence.  When completed, it will be the largest great ape facility in North America and one of the first worldwide to include all four types of great ape – bonobos, chimpanzees, gorillas and orangutans – for noninvasive interdisciplinary studies of their cognitive and communicative capabilities.  Great Ape Trust is dedicated to providing sanctuary and an honorable life for great apes, studying the intelligence of great apes, advancing conservation of great apes and providing a unique educational experience about great apes.