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Curse of the Cannibal Ferrets

Ferrets have a more interactive social life than previously recognised and this, combined with the recently discovered fact that ferrets will scavenge dead ferrets, means a greater risk of the spread of tuberculosis in New Zealand.

That's the initial findings of a six-month study by Otago University student Justine Ragg, who is studying ferrets and their role in tuberculosis infection through an AgResearch PhD award.

Ferrets carry Tb and have been implicated in the wildlife transmission of tuberculosis to stock. Although New Zealand has the largest population of feral ferrets in the world we know little about them, and even less about the dynamics of Tb infection in their population.

Ragg has been studying a population of ferrets on three farms in Palmerston, East Otago. This has included radio-tracking 23 ferrets to study their movements and denning habits. The initial data she's built up has already shown some interesting details of ferret social behaviour. It was thought ferrets were solitary and territorial animals like other mustelid species, but the study found that individual home ranges overlapped considerably and that den sharing was common, particularly in woolsheds and haysheds.

These results indicate that ferrets are interacting with one another much more than previously thought and this may have some bearing on the transmission of disease through their population.

Analysis of the implications of this study is continuing, with Ragg now examining the ferrets' diet. Previous research found that more males were infected with Tb than females and this could be related to dietary differences between the sexes.

Night surveillance using night vision time-lapse videos was also used to study the scavenging behaviour of ferrets, clearly showing them eating a variety of carrion including dead ferrets.

While it is accepted that ferrets may be a possible vector, there is much scientific debate about whether ferrets can infect one another and so maintain the disease in their own population. The preliminary results of this study present some explanation of how Tb could be maintained and spread within ferret populations.

Ragg suggests the large number of ferrets denning around haysheds may also have implications in the spread of Tb to cattle.