Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Size does matter when choosing a mate

10.08.2004


The difference in size between males and females of the same species is all down to the battle for a mate, according to a study of shorebirds published by British scientists today (August 9 2004).

The findings, published in the Proceedings of the National Academy of Sciences, are the first explanation for a rule identified over forty years ago by German scientist Bernhard Rensch.

Rensch’s rule, as it has become known, says that the ratio between the sizes of the sexes is related to body size with very few exceptions throughout the animal kingdom - for example, male gorillas are much bigger than female gorillas, whereas male rats are only slightly larger than female rats.



In this new research, scientists from the Universities of Bath, Oxford and East Anglia, carried out complex statistical analyses of the mating behaviour, body size and ecology of more than 100 different shorebird species from around the world.

They found that in larger shorebirds the battle between males for a mate is highly competitive and larger size offers an advantage over other potential suitors as they battle aggressively on the ground. The evolutionary result is that male Ruffs, a large shorebird, are about twice the size of females.

For smaller species, such as Dunlins, battles take place in the air and agility and smallness become more important factors. The result is that Dunlin males are smaller than the females.

Although biologists thought that sexual selection must be playing a role in driving Rensch’s rule, until now nobody had been able to prove exactly how it worked. Although the research was conducted on shorebirds, the researchers are confident that that the same driver is in operation in everything from mites to primates throughout the animal kingdom.

Dr Tamas Szekely from the University of Bath who led the project, said: “We have known about Rensch’s rule for many years but didn’t have a clue what drives it. Many biologists had considered sexual selection to be the most likely answer, but nobody really knew how.”
“Once we started analysing the data the story shaped up perfectly. I believe that sexual selection is the driver behind Rensch’s rule throughout the animal kingdom and we are already finding this is the case in other bird species we are studying such as Bustards,” said Szekely. “There’s no reason why it would not apply in many other animals from gorillas living on the rainforest floor to monkeys living high up in the canopy too.”

Shorebirds, gulls and auks are the ideal group to test theories explaining Rensch’s rule as the body mass of male shorebirds ranges from 59 per cent to 169 per cent of female body mass, encompassing nearly the entire range exhibited by the world’s 9,700 species of birds. Shorebirds also encompass the full range of mating systems including social polygyny (males have more than one female at a time), social monogamy (one partner at a time), and polyandry (females have more than one male at a time). The researchers collected data on body size, mating behaviour, ecology and life histories from existing literature and analysed them with a suite of statistical tools.

The researchers also found that where there is high competition between males, the difference in the ratio between the sizes of the sexes increases, explaining the changing ratios identified by Rensch. In contrast, in species with low intensity of male-male competition, females tend to be the larger of the sexes.

Andrew McLaughlin | alfa
Further information:
http://www.bath.ac.uk

More articles from Life Sciences:

nachricht Kidney tumor: Genetic trigger discovered
18.06.2018 | Julius-Maximilians-Universität Würzburg

nachricht New type of photosynthesis discovered
18.06.2018 | Imperial College London

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

Im Focus: Water is not the same as water

Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.

From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Novel method for investigating pore geometry in rocks

18.06.2018 | Earth Sciences

Diamond watch components

18.06.2018 | Process Engineering

New type of photosynthesis discovered

18.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>