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THERE has been a precipitous decline in red squirrel (Sciurus vulgaris) numbers in Britain over the past 50 or more years and they are now effectively extinct from most counties in England and Wales. The main reason for this is believed to be mortality caused by squirrelpox virus, which is carried asymptomatically by the introduced North American grey squirrel (Sciurus carolinensis). The remaining stronghold of red squirrels in the UK is in Scotland, with fragmented or isolated populations surviving elsewhere, including Brownsea Island, the Isle of Wight (IoW) and Jersey.
Much of the research into red squirrel decline has concentrated on squirrelpox, but a recent study investigated other causes of mortality (Simpson and others 2013b). Four of the 163 squirrels examined – three from the IoW and one from Brownsea Island – had gross, crusty thickening of the pinnae, sometimes with keratinised or wart-like protuberances (Fig 1). One of the IoW cases also had a single, clearly circumscribed wart-like growth on the bridge of the nose and on one flank, similar lesions on …