20 agosto 2009

Checking on Tasmanian Devils' Facebook to Save Them

Well, it is not really Facebook, but analyses of the social network of Tasmanian Devils, a threatened species on the brink of extinction because of an infectious disease, are used to help in their conservation.

The Tasmanian Devil (Sarcophilus harrisii) is the largest extant carnivorous marsupial. Its populations have suffered severe declines due to an infectious cancer, the devil facial tumour disease (DFTD). DFTD is an aggressive non-viral transmittable parasitic cancer. It produces facial tumors that interfere with feeding, and the affected animal starve to death. DFTD has ravaged Tasmania's wild devils, with declines up to 50% of the population.

Determining exactly how the animals interact could improve control efforts, but few studies have managed to reproduce social networks. Rodrigo K. Hamede and colleagues of the School of Zoology of the University of Tasmania, Australia, have just published in Ecology Letters their research on the structure of the contact network between individuals, a key factor on the transmission of infectious disease.

These researchers used a novel technology, proximity sensing radio collars, that detects when two animals came close to each other. These collars were fitted into 27 devils. Results indicate that all studied devils were connected in a single giant component. Since all animals are therefore connected directly or indirectly to every other animal, diseases would easily spread throughout the network from any single infected individual. More male-female contact occurred during mating season, while females interacted more frequently with females during non-mating periods.

These results suggest that there is limited potential to control the disease by targeting highly connected age or sex classes. The team was unable to find one sex or age group that had more connections than others. That information might have allowed control programs to stanch the spread of disease by targeting the most connected class.

Photographs: Wikipedia & author

Access the scientific article: Hamede, R.K. et al. 2009. Contact networks in a wild Tasmanian devil (Sarcophilus harrisii) population: using social network analysis to reveal seasonal variability in social behaviour and its implications for transmission of devil facial tumour disease. Ecology Letters DOI: 10.1111/j.1461-0248.2009.01370.x

See Journal Watch Online Blog Entry: http://journalwatch.conservationmagazine.org/2009/08/20/ties-that-bite/

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