Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Starvation is the norm for birds and mammals

22.07.2005


It is difficult to find out whether animals in the wild have enough food, but research suggests that they are hungry most of the time, according to a new paper published in the American journal, Science, on Friday 22 July.



Researchers at the University of Reading also argue that this surprising conclusion could provide valuable new insights into animal behaviour.

The researchers undertook an analysis of a huge data base, the Global Population Dynamics Database (1), in which the changes over time in population densities of animals in many different environments are archived.


Using 1,780 of these ‘time series’ of mammals, birds, fish and insects, the Reading scientists have shown that populations are generally more abundant than their environments can support long term. Put together with earlier results that populations of birds and mammals are limited by their food supplies, it follows that these animals are generally short of food.

The first step of the analysis was to calculate the relationships between population’s growth rates and their densities. Natural populations of animals are expected to increase when their densities are less than the environment can support long term, because individuals then have abundant food for reproduction and maintenance. If their densities are higher, however, then population declines become inevitable.

“The precise relationship between a population’s growth rate and its density determines the way population density changes over time,” said Professor Richard Sibly, the lead researcher on the study. “The simplest possibility would be a straight-line relationship. This is not what was found.

“Rates of population growth are high at low population densities, as expected, but contrary to previous predictions, they decline rapidly with increasing population size, and then flatten out, for all four animal groups.

“This produces a strongly concave relationship between a population’s growth rate and its size. It is this that leads to the conclusion that animals will be found living at densities above those the environment can support long term.”

Professor Sibly suggests that such a conclusion could tell us a great deal about the ways animals compete with each other for food.

He said: “We are now investigating two theories. The first theory holds that the principal competition is between juveniles and adults. When population densities are low, reproduction is very successful and many juveniles are added to the population and many of them survive, so the population grows rapidly. On the other hand, when there are more animals than the environment can support, then it is the juveniles that suffer. The adults get what they need but most of the juveniles die. The result is that the population declines slowly as adults die, without any births to replace the deaths.

“The second theory applies when food is dispersed over territories. In the extreme case, the number of territories is fixed. When population densities are low, reproduction is very successful , so the population grows rapidly, as before. When there are more animals than the environment can support, then only some of the animals get territories. Since the number getting territories is fixed, the surplus population dies.”

Craig Hillsley | alfa
Further information:
http://www.reading.ac.uk

More articles from Ecology, The Environment and Conservation:

nachricht International network connects experimental research in European waters
21.03.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

nachricht World Water Day 2017: It doesn’t Always Have to Be Drinking Water – Using Wastewater as a Resource
17.03.2017 | ISOE - Institut für sozial-ökologische Forschung

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>