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 Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.

nachricht 100 % Organic Farming in Bhutan – a Realistic Target?
15.06.2018 | Humboldt-Universität zu Berlin

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: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

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...

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

Graphene assembled film shows higher thermal conductivity than graphite film

22.06.2018 | Materials Sciences

Fast rising bedrock below West Antarctica reveals an extremely fluid Earth mantle

22.06.2018 | Earth Sciences

Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>