An international team of scientists has overturned an ecological study on how some animals search for food. Previously it was believed that wandering albatrosses and other species forage using a Lévy flight strategy - a cluster of short moves connected by infrequent longer ones. Published this week in the journal Nature, the team discovered that further analyses and new data tell a different story for the albatrosses and possibly for other species too.
Biologists and physicists identified 'Lévy flights', named after the French mathematician Paul Lévy, as an efficient way for animals to search for sparse food. They have been attributed to a wide range of organisms, including zooplankton, grey seals, spider monkeys and even Peruvian fisherman.
The first attempt to demonstrate their existence in a natural biological system suggested that wandering albatrosses perform Lévy flights when searching for prey on the ocean surface - a finding followed by similar inferences about the search strategies of deer and bumblebees. However, this research shows this is not the case. Based on new high-resolution data collected from loggers attached to the legs of wandering albatrosses on the sub-Antarctic island of South Georgia, the team show that the previous claims about the Lévy flight behaviour were unfounded. They also re-analysed the existing data sets for deer and bumblebees using new statistical methods, again finding that none exhibits evidence of Lévy flights.
"It now seems the albatrosses come across food at simpler random intervals", says lead author Dr Andrew Edwards from British Antarctic Survey (now at Fisheries and Oceans Canada). "Our work also questions whether other animals thought to exhibit Lévy flights really do all forage in the same way."
This research improves scientists' understanding of the foraging behaviour of the wandering albatross - an endangered species. It may also help develop a new theory for how animals forage - an essential piece in the wider ecological jigsaw puzzle.
Issued by the British Antarctic Survey Press Office.
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Notes for Editors
Still images and video (DV-cam) are available of albatrosses at British Antarctic Survey's Bird Island Research Station. Please contact the BAS press office as above.
Revisiting Lévy flight search patterns of wandering albatrosses, bumblebees and deer by Andrew M. Edwards, Richard A. Phillips, Nicholas W. Watkins, Mervyn P. Freeman, Eugene J. Murphy, Vsevolod Afanasyev, Sergey V. Buldyrev, M.G.E da Luz, E. P. Raposo, H. Eugene Stanley, Gandhi M. Viswanathan is published in the journal Nature on Thursday 25 October 2007.
Organisations involved in this research: British Antarctic Survey, Boston University (US), Yeshiva University (US), Universidade Federal do Parana (Brazil), Universidade Federal de Pernambuco (Brazil), Universidade Federal de Alagoas (Brazil).
A Lévy flight is named after the French mathematician Paul Pierre Lévy and is a type of random walk in which increments are distributed according to a probability distribution with a heavy power law tail.
The work at BAS forms part of the COMPLEXITY and DISCOVERY 2010 science programmes at BAS. NATURAL COMPLEXITY provides a new perspective on, and understanding of, complicated natural phenomena including biological food webs, animal foraging and iceberg calving. DISCOVERY 2010 is investigating and describing the response of an ocean ecosystem to climate variability, climate change and commercial exploitation.
The original study was published in Nature in 1996 based on albatross data collected from Bird Island Research Station in 1992. Another Nature paper in 1999 developed this idea further using data from bumblebees and deer and using computer simulation.
The wandering albatrosses inhabit Bird Island, a 5km-long rocky island off South Georgia in the South Atlantic Ocean. With no food to be found on the island, the birds undertake long foraging trips, flying close to the ocean surface to spot and feed on squid. Loggers attached to the birds' legs tell ecologists how often the birds land on the water to feed.
Estimates suggest that 300,000 seabirds are killed annually in the world's long-line fisheries, many of which are albatrosses. Since 2001, by-catch rates in well-regulated fisheries have decreased substantially, remained stable in less well-regulated ones and probably increased in pirate fisheries, for which no real data exist. 19 of the 21 species of albatross are threatened with extinction.
British Antarctic Survey is a world leader in research into global issues in an Antarctic context. It is the UK's national operator and is a component of the Natural Environment Research Council (www.nerc.ac.uk). It has an annual budget of around £40 million, runs nine research programmes and operates five research stations, two Royal Research Ships and five aircraft in and around Antarctica. More information about the work of the Survey can be found at: www.antarctica.ac.uk
Fisheries and Oceans Canada
Fisheries and Oceans Canada is the lead federal government department responsible for developing and implementing policies and programs in support of Canada's economic, ecological and scientific interests in oceans and inland waters.
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