This paper describes the denning behaviour of 24 feral ferrets Mustela furo
on farmland, East Otago, South Island, New Zealand. One hundred and ninety
seven dens were located and radio-collared ferrets were found to share den
s simultaneously with other ferrets on 7.4% of 706 radio-tracking events an
d used dens that had been previously used by other ferrets (sequential den
sharing) on 44.3% of occasions. In this particular study, ferrets were exhi
biting a higher degree of sociality than has been recorded in other solitar
y mustelid species and therefore may not be adhering to the model of intras
exual territoriality thought to apply to other mustelid species. Den sharin
g may be a mechanism by which bovine tuberculosis Mycobacterium bovis is tr
ansmitted within ferret populations. Over 80% of the sequential den sharing
occurred within 14 days, well within the survival span of M. bovis bacilli
. Denning of infected ferrets in haybarns may pose a risk of transmission o
f M. bovis to livestock from hay.