Seabirds' movement patterns tied to what fishermen toss away

Jan 28, 2010

Humans and human activities have clearly altered the Earth's landscape and oceans in countless ways, often to the detriment of other plants and animals. But a new report published online on January 28th in Current Biology shows just what a tangled food web we've woven. Two species of Mediterranean seabirds change their every move based on the activities of local fisheries and, in particular, the fish that people toss away. The seabirds' shifting movement patterns can be seen at the regional scale.

"We show that human activities in the natural environment can promote critical transitions in the spreading properties of foraging animals by locally changing the predictability and availability of their resources," said Frederic Bartumeus of Princeton University and Institut CatalĂ  de Cičncies del Clima in Spain. "Our study suggests an elementary but often disregarded connection between human local resource exploitation and global movement patterns of organisms."

The findings may have important implications for conservation biology and the study of invasive species, the researchers said. The work also provides a solid statistical framework for quantifying movement patterns across ecological scales, which can now be applied to other species and other circumstances.

Bartumeus' team took advantage of existing satellite data on the Cory's shearwater and the Balearic shearwater, which tracked the seabirds' movement over multiple foraging trips. Each trip typically lasts less than two days and covers distances anywhere from 10 to 1000 kilometers. Because the fisheries don't operate on holidays and weekends, the researchers were able to characterize the birds' activities in the presence and in the absence of the fisheries' trawling activities.

When the fisheries don't operate, essentially combine local searching with very large traveling distances, Bartumeus explained. Such a multiscale search pattern generates what he calls superdiffusive movement properties, meaning that the birds spread out from one another at a rate that accelerates over time. "Such a movement pattern allows for efficient explorations when the birds are looking for their natural prey of small fish and squid, which are highly mobile and unpredictably distributed in space and time," he said.

In contrast, when fishermen are discarding fish, seabirds perform local searches around the boats, which act as an "attracting force." As a result of such confined movement, the spreading of scavenging seabirds in the seascape decelerates with time, and movement patterns involve well-defined spatial scales related to the fishery activity.

In a nutshell, says Bartumeus: "Fishery activities impact the foraging ecology of seabirds at much larger spatiotemporal scales than one might expect intuitively. The macroscopic spreading properties of seabirds through the seascape are directly influenced by the presence of fishermen's boats discarding ."

Explore further: The right amount of grazing builds diverse forest ecosystems

Related Stories

Black rat does not bother Mediterranean seabirds

Oct 02, 2009

Human activities have meant invasive species have been able to populate parts of the world to which they are not native and alter biodiversity there over thousands of years. Now, an international team of scientists ...

New study reveals large scale conservation essential

Jun 10, 2008

Scientists were surprised with findings of a recent study that reveals many animal species believed to persist in small contained areas actually need broad, landscape level conservation to survive.

Seabird research tracks ocean health

Feb 22, 2008

Oxford University scientists hope to uncover the secret life of an important British seabird using technology developed with Microsoft Research Cambridge.

Some Ningaloo Reef fish are 'homebodies'

Jun 18, 2009

New research shows that some fish species in Western Australia's Ningaloo Marine Park spend most of their time close to home, staying on the reef rather than travelling significant distances, as was previously thought.

NOAA bans commercial harvesting of krill

Jul 13, 2009

The National Oceanic and Atmospheric Administration (NOAA) today published a final rule in the Federal Register prohibiting the harvesting of krill in the Exclusive Economic Zone (EEZ) off the coasts of California, Oregon, ...

Recommended for you

Seeds keep vital much longer when stored without oxygen

4 hours ago

If seed breeding companies, gene banks and the Svalbard Global Seed Vault on Spitsbergen should store plant seeds under oxygen-poor conditions, it would be possible to store them for much longer while still ...

Native species may be hindering fox control efforts

4 hours ago

Native species interfering with ground distributed baits used to control red foxes in south west Western Australia may mean the baits are not available to the target species, a Murdoch University study has ...

Giant anteaters kill two hunters in Brazil

Jul 26, 2014

Giant anteaters in Brazil have killed two hunters in separate incidents, raising concerns about the animals' loss of habitat and the growing risk of dangerous encounters with people, researchers said.

Study indicates large raptors in Africa used for bushmeat

Jul 24, 2014

Bushmeat, the use of native animal species for food or commercial food sale, has been heavily documented to be a significant factor in the decline of many species of primates and other mammals. However, a new study indicates ...

User comments : 0