Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The rule of the game

25.03.2002


Every kilogram of predator needs a fixed amount of prey.



Every kilogram of meat-eating mammal needs 111 kilograms of prey to sustain it, say two ecologists. The rule holds from weasels to bears.

With many species of carnivore endangered, the discovery could help conservationists work out how to maintain a species’ resource base.


Chris Carbone, of the Institute of Zoology, London, and John Gittleman, of the University of Virginia, found the rule when they compared the population densities of 25 species of carnivore with the population densities of their prey1.

The relationship between the mass of predator and prey holds regardless of the animals’ diet or habitat. It covers European badgers, which eat mainly worms, and big cats, for example. The smallest carnivore analysed was the 140-gram least weasel, the biggest the 310-kilogram polar bear.

"To see this rule emerging across a wide range of carnivores was a real surprise to me, and I think it’ll surprise a lot of ecologists," says Carbone. He expects similar rules to hold for other predatory groups, such as reptiles.

"Most models [of carnivore populations] have assumed that resources aren’t limiting, but that the rate of their acquisition is," says ecologist Pablo Marquet of the Catholic University of Chile, Santiago. "This shows that what really matters is the resources you have."

The result means that global biological patterns may only become apparent by looking at detailed local information, such as diet and population number, Marquet adds. "Some researchers ignore local knowledge in the hope that it will average out and you’ll keep the big picture," he says.

Rule tool

The rule will be "a very useful ballpark figure" for conservationists, says Carbone. They could use it to predict the population densities of species not included in the analysis.

Carbone intends to apply it to the conservation of the Sumatran tiger. These tigers live around oil-palm plantations, and eat mainly wild pigs. Estimating the weight of the pig population will give an idea of how many tigers an area can sustain.

And where a carnivore-to-prey ratio falls much below 1/111, it could be a clue that something else, such as inbreeding, is keeping its numbers down.

The new rule is one of several general patterns to emerge recently from studies of how organisms’ biology varies with their size. Last month, for example, researchers announced that the ratio of above- to below-ground tissue is constant across a wide range of plants2.

References
  1. Carbone, C. & Gittleman, J.L. A common rule for the scaling of carnivore density. Science, 295, 2273 - 2276, (2002).
  2. Enquist, B.J. & Niklas, K.J. Global allocation rules for patterns of biomass partitioning in seed plants. Science, 295, 1517 - 1520, (2002).


JOHN WHITFIELD | © Nature News Service

More articles from Life Sciences:

nachricht During HIV infection, antibody can block B cells from fighting pathogens
14.08.2018 | NIH/National Institute of Allergy and Infectious Diseases

nachricht First study on physical properties of giant cancer cells may inform new treatments
14.08.2018 | Brown University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

Im Focus: World record: Fastest 3-D tomographic images at BESSY II

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

'Building up' stretchable electronics to be as multipurpose as your smartphone

14.08.2018 | Information Technology

During HIV infection, antibody can block B cells from fighting pathogens

14.08.2018 | Life Sciences

First study on physical properties of giant cancer cells may inform new treatments

14.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>