Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nevada researcher re-ignites mammal reproduction debate

23.08.2004


Zebra Mare and Foal. Photo by Elissa Cameron


Study findings could have major impact on wildlife control and agriculture production

One of the most debated hypotheses in evolutionary biology received new support today, thanks to a study by a scientist at the University of Nevada, Reno. Elissa Cameron, a mammal ecologist in the Department of Natural Resources and Environmental Science, has helped to disprove critics of a scientific theory developed in 1973.


At that time, ecologist Bob Trivers and mathematician Dan Willard said that large healthy mammals produce more male offspring when living in good conditions, such as areas where there is an ample food supply. Conversely, female mammals living in less desirable conditions would tend to have female offspring.

According to Cameron, the hypothesis demonstrated the idea that having more male offspring leads to greater evolutionary success for mammal parents, if living conditions support larger populations. Should conditions be less desirable, having female offspring would be a better investment for mammal parents.

"Male zebras can father more than a hundred offspring in a lifetime, whereas female zebras are constrained to minimal reproductive rates--about one a year," Cameron said. "Sons, therefore, offer higher breeding rates to zebra parents, while female offspring are a lower-risk investment.

"Therefore, if the animal’s living conditions aren’t suitable, giving birth to a female would better ensure the animal’s genetic success in the long term. Daughters of less healthy mothers would out-reproduce sons in poorer conditions because males that are unsuccessful in having mates have few offspring while most females breed throughout their lifetime."

The problem with this idea is that, until now, only about 30-percent of studies have supported the hypothesis, which has been debated because there have been so many studies that have attempted to test the idea. The results have been contradictory--some find support for the hypothesis, some do not, Cameron said.

But in a journal article published today in the "Proceedings of The Royal Society of London: B," a journal of the independent scientific academy in the United Kingdom, Cameron asserts that there’s a good reason to support the hypothesis.

It could all boil down to the amount of glucose, or blood sugar, in a female mammal’s body around the time of conception, Cameron said.

She conducted an analysis of 1,000 studies that examined the Trivers-Willard hypothesis and sex ratios in mammals. Her study found that female mammals that were in better body condition during the early stages of conception were more likely have male offspring. Body fat and diet can affect levels of glucose circulating in a mammal’s body, and Cameron suggests that the levels of glucose around the time of conception could be influencing the sex of the animal’s offspring.

"A high-fat diet can result in higher levels of glucose, thereby supporting the hypothesis that glucose may be contributing to the sex of the mammal’s offspring," Cameron said.

This finding is key to the Trivers-Willard debate, and if supported in future studies, Cameron’s theory could have dramatic influence on wildlife control and animal production.

"If you can get dairy cows to have more female calves, it would have huge implications for the dairy industry," she said.

Cameron said she would like to test her hypothesis by reducing the amount of glucose in selected populations of wild mammals. An injected steroid can block glucose circulation, and potentially increase the number of female offspring, while in the long term the same result may be accomplished through diet.

Such a study would be able to show whether mammal populations in different regions could be increased or decreased, based on the needs of those areas, she said. In eastern Nevada, for example, declining populations of mule deer could be better researched by taking into account Cameron’s contribution to the decades-old scientific controversy.

Though her analysis has rekindled debate of the Trivers-Willard hypothesis, and its implications for mammal ecology, Cameron said that she hopes her broader accomplishment would be to generate further inquiry.

"Right or wrong, the journal article will spark research to confirm or deny my theory about the role of glucose in determining gender in reproduction," she said. "The idea is that it will hopefully encourage more research."

Bob Conrad | EurekAlert!
Further information:
http://www.unr.edu

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling 'fast fashion' to reduce waste and pollution
03.04.2017 | American Chemical Society

nachricht Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Scientist invents way to trigger artificial photosynthesis to clean air

26.04.2017 | Materials Sciences

Ammonium nitrogen input increases the synthesis of anticarcinogenic compounds in broccoli

26.04.2017 | Agricultural and Forestry Science

SwRI-led team discovers lull in Mars' giant impact history

26.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>