Tasmanian Devils’ Cancer Tackled Through Social Networks Study

By Alex Morales

Aug. 19 (Bloomberg) -- Tasmanian devils, fighting a deadly facial cancer that threatens to wipe out the species, could be saved by radio collars and an analysis of their social network.

A study of 27 of the usually solitary carnivores in Tasmania’s Narawntapu National Park showed all were connected to each other directly or through other individuals, with one male holding a central role within the network, according to a study that appeared today in the Ecology Letters journal.

The Tasmanian marsupial’s population fell by 60 percent in a decade from a fatal cancer called Devil Infectious Tumor Disease, the International Union for Conservation of Nature said. The Swiss-based group last year listed the devil as “endangered,” the second-highest degree of extinction threat.

“Understanding networks of contacts is crucial because it is usually the case that a small number of highly connected individuals, or ‘super spreaders,’ are responsible for the majority of disease transmission,” said Rodrigo Hamede, the paper’s lead author and a zoologist at the University of Tasmania. “Once these individuals are identified, actions such as targeted treatment or culling may control the disease.”

The facial cancer is spread through biting, and previous studies revealed transmission is more common during the February-March mating season, the paper said. Because mating occurs in underground burrows, past observations have been “sparse,” Hamede’s team said.

Devil Interactions

The researchers fitted 23 female devils and 23 males with radio collars that logged “contact” when they came within 30 centimeters (12 inches) of another tagged animal from February through June 2006. Usable data was recovered from 27 of the animals. The scientists’ focus was on interactions between individuals rather than incidence and transmission of the tumor.

The scientists found that during the mating season, contact between individual devils was more likely to be between males and females while outside the breeding period, female-female encounters were more common. At all times, interactions between males were “relatively uncommon.”

As few as 10,000 mature adult devils remain, confined to the Australian island-state of Tasmania, according to the IUCN. The tumor is found across 60 percent of the devil’s territory, with the group predicting a further decline in the animals’ population of 70 percent over the next decade.

While the studied population revealed one male who was a hub between many individuals, the researchers were unable to determine a specific age or sex-group that is more likely to interact with other devils.

“Our results suggest that there is limited potential to control the disease by targeting highly connected age or sex classes,” the researchers wrote. Because all the devils were connected, “The disease is capable of spreading to each individual in the population once one individual is infected.”

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