Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Food Fight: Wolves Pack Up to Out-eat Ravens

23.08.2004


New research on the wolves of Isle Royale may shed light on a mystery that has long puzzled biologists: Why do some predators band together to hunt?

"Most species of predators live solitary lives," says John Vucetich, a research assistant professor of wildlife ecology at Michigan Technological University. "Biologists have always wanted to know why the few exceptions live in groups."

In his observations of wolves and ravens, Vucetich may have found the answer: Predators that hunt in groups lose far less meat to scavangers. Earlier, scientists had guessed that wolves hunting in a large pack would bring down more food per wolf, so each individual would get more to eat. However, studies showed that wasn’t the case. "According to their calculations, wolves in big packs got less food," Vucetich said. "It didn’t make sense."



So Vucetich examined the methodology and discovered a problem. Scientists had calculated the amount of food available based on the weight of the prey killed, not on the amount that the wolves actually ate. "Then I thought, ’OK, what you kill isn’t relevant; it’s what you consume,’" he said. "What happens after the kill? Suddenly, scavengers are really important."

For wolves, ravens are the really important scavengers. "You never see wolves without ravens nearby," Vucetich said. "They are ubiquitous at kills." On Isle Royale National Park, located in Lake Superior, five to 15 ravens are found on the carcasses of moose killed by wolves. And on the mainland, the numbers can be far higher: About 100 ravens were once counted around the carcasses of a few wolf-killed deer.

"So we asked the questions: How much can a raven take per day? It can eat and stash about two pounds. How much can a wolf eat? Up to 18 pounds in a few hours," Vucetich said. "We put the pieces together, and we found that in bigger packs, both the pack and the individuals actually get more food, not less."

Ravens are intelligent, fast and agile. It’s useless for wolves to waste energy chasing them away from a carcass because the ravens come right back, so they don’t. Instead, wolves simply out-eat the ravens, and thus the advantage of a large pack becomes clear.

Based on his discovery, Vucetich thinks any predator that hunts large prey has to have some strategy to deal with scavengers. They can make their kills in dense cover, like tigers, or haul the carcass off to a secluded spot, like leopards. Lions usually hunt in groups, which helps when a gang of hyenas shows up.

Solitary hunters can find themselves at a loss when confronted with unexpected scavengers. "A colleague of mine saw a mountain lion kill an elk in the open," Vucetich said. Mountain lions usually hide their large prey after a kill, and their behavior hasn’t adapted to deal with scavanging ravens. "Ravens found the kill, and the mountain lion went nuts trying to chase them away.” "The moral of the story is, if you’re eating something big, you have to have a way to deal with scavengers."

Vucetich’s work is supported by the National Science Foundation, Isle Royale National Park and Earthwatch. His article, “Raven Scavenging Favours Group Foraging in Wolves,” has been published in the June 2004 edition of the journal Animal Behaviour and is posted online at http://dx.doi.org/10.1016/j.anbehav.2003.06.018 The co-authors are Rolf Peterson, of Michigan Technological University, and Thomas Waite, of Ohio State University.

| newswise
Further information:
http://www.mtu.edu

More articles from Life Sciences:

nachricht Discovery of a Key Regulatory Gene in Cardiac Valve Formation
24.05.2017 | Universität Basel

nachricht Carcinogenic soot particles from GDI engines
24.05.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>