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 New application for acoustics helps estimate marine life populations
16.01.2018 | University of California - San Diego

nachricht Unexpected environmental source of methane discovered
16.01.2018 | University of Washington Health Sciences/UW Medicine

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

White graphene makes ceramics multifunctional

16.01.2018 | Materials Sciences

Breaking bad metals with neutrons

16.01.2018 | Materials Sciences

ISFH-CalTeC is “designated test centre” for the confirmation of solar cell world records

16.01.2018 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>