Mortalities, amyloidosis and other diseases in free-living red squirrels (Sciurus vulgaris) on Jersey, Channel Islands

Between 2007 and 2014, 337 free-living red squirrels (Sciurus vulgaris) on Jersey, Channel Islands, were examined post mortem as part of a mortality and disease surveillance scheme. Road traffic accidents (RTAs) were attributable for 50.7 per cent (171/337) of the casualties, 34.4 per cent (116/337) succumbed to diseases including fatal exudative dermatitis (FED), 7.1 per cent (24/337) to predation, 6.5 per cent (22/337) to other trauma and 1.2 per cent (4/337) to suspected poisoning. Cat predation accounted for 5 per cent (17/337) of mortalities. Pathologies were diverse and individual animals were often identified with more than one disease process. Squirrelpox virus (SQPV) particles were not detected in selected cases examined by transmission electron microscopy (TEM). Amyloid was identified in 19.3 per cent (65/337) of squirrels, often in conjunction with inflammatory lesions like hepatic capillariasis. A consistent cause of amyloid accumulation was not identified, although there was a significant association of amyloidosis with hepatic capillariasis and FED. In addition to RTAs, amyloidosis and FED have been identified as important causes of squirrel morbidity and mortality on Jersey, while the underlying aetiology and predisposing factors for these two disease complexes are presently unclear. Disease, fragmented woodlands, an increasingly suburban habitat, along with various anthropogenic factors, may jeopardise the long-term viability of this island red squirrel population.