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 Study suggests oysters offer hot spot for reducing nutrient pollution
17.10.2017 | Virginia Institute of Marine Science

nachricht World first for reading digitally encoded synthetic molecules
17.10.2017 | CNRS

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

Im Focus: New nanomaterial can extract hydrogen fuel from seawater

Hybrid material converts more sunlight and can weather seawater's harsh conditions

It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Study suggests oysters offer hot spot for reducing nutrient pollution

17.10.2017 | Life Sciences

Breaking: the first light from two neutron stars merging

17.10.2017 | Physics and Astronomy

World first for reading digitally encoded synthetic molecules

17.10.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>