Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Female monkeys more dominant in groups with relatively more males

22.07.2008
Female monkeys are more dominant when they live in groups with a higher percentage of males.

This is caused by self-organisation. This surprising discovery was made by researchers at the University of Groningen. What makes the study particularly interesting is that the researchers used a computer model which can simulate interaction between monkeys. Their findings are published in the journal Plos One.

Many animals living in groups have a social hierarchy, a so-called ‘pecking order’. Monkeys, too, have a social hierarchy. Highest in the pecking order is the most dominant monkey, who consistently wins aggressive interactions (such as biting) with other group members. At the bottom of the hierarchy is the lowest ranking monkey, who consistently loses interactions with other members of the group. Monkeys have to fight for their place in this hierarchy every day.

Simulation

The position of females in the hierarchy varies among different monkey species. In most species females are ranking below the males. This is no wonder, because they are usually much smaller than males. However, in the case of the Lemur species of Madagascar the females are dominant, in bonobos, males and females roughly equal each other in dominance, and among a lot of other species (macaques and the grivet, for instance) females are weakly dominant (this means that the most dominant females rank above approximately a third of the males).

‘Until now, it was unknown how this female dominance develops’, says Charlotte Hemelrijk, theoretical biologist at the University of Groningen and the first author of the article which she wrote together with Dr. Jan Wantia and a Swiss anthropologist, Dr. Karin Isler. Researchers in Groningen therefore created a virtual world, Domworld, with which they could simulate the interactions between monkeys.

Large amount of literature

Surprisingly, the computer model predicted females to be more dominant in a group with a relatively large number of males. To verify this prediction, the researchers analyzed data of aggression of a large amount of literature in which primate behaviour is described in order to calculate for the first time female-dominance among many different groups and monkey species. Their analysis showed the predictions of the computer model to be accurate. ‘This is an interesting way of conducting research’, says Hemelrijk. ‘You discover something unexpected in the virtual world and then you test your findings in the real world.’

Inborn or self-organisation?

So why are females more dominant in groups with a higher percentage of males? Two competing theories about the development of dominance exist, explains Hemelrijk. ‘According to the first theory, dominance is inborn. A monkey with good genes is bigger and will therefore win aggressive interactions more easily. The second theory states that dominance develops through self-organisation. An individual monkey wins an aggressive interaction by chance. As a consequence, the monkey’s self-confidence grows and it also wins other aggressive interactions. It’s a self-reinforcing effect,’ says Hemelrijk.

More complex than thought

If the first theory were correct, one would expect dominant females to be relatively bigger in size compared to male members of their species than less dominant females of other species. The researchers found this not to be the case. Instead, the second theory turns out to perfectly explain female dominance, as the relation between female dominance and the percentage of males can only be found among monkey species living in groups with aggressive behaviour that is sufficiently intense and frequent.

‘Male aggression is more intense than that of females. In groups with more males, males are more often defeated by other males. Consequently, high-ranking females may be victorious over these losers. Furthermore, the presence of more males in the group leads to more interactions between males and females, causing more chance winnings by females. Through a self-reinforcing effect, these females will go on to win more frequently in later interactions and grow more dominant’, says Hemelrijk.

Human interaction

According to the researcher, the study casts new light on monkeys. ‘The assumption was always that the degree of female dominance over males -or male dominance over females- was static, but it turns out to be much more dynamic and complex than expected.’ Dominance also plays a factor of importance in human interaction, says Hemelrijk. ‘It would not surprise me if self-organisation would prove to play a role in the development of dominance between the sexes among human beings too.’

| alfa
Further information:
http://www.rug.nl
http://www.rug.nl/Corporate/nieuws/archief/archief2008/persberichten/087_08

Further reports about: Hemelrijk Interaction dominance hierarchy relatively self-organisation

More articles from Life Sciences:

nachricht Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care

nachricht Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>