From February 1998 to July 1999, 65 western gray squirrels (Sciurus griseus
griseus) were trapped at three sites in Klickitat County, Washington (USA)
as part of a home range and habitat use study. No squirrels (0/9) with man
ge lesions were identified in the initial trapping session (February and Ma
rch 1998) During all subsequent trapping sessions (August 1998 through July
1999), squirrels with lessions consistent with notoedric mange, caused by
the mite Notoedres centrifera (douglasi), were captured or recaptured at al
l three study sites. The diagnosis was confirmed by histopathology and exam
ination of mites obtained from skin scrapings from two affected squirrels.
Of the 56 squirrels captured from August 19 July 1999, 33 (59%) had charact
eristic mange lesions, and 14 (42%) affected squirrels died directly of man
ge or of secondary complications of mange. Only four breeding females of 22
radio-collared animals (males and females in the study population were kno
wn to have survived the mange outbreak (12 died, 6 missing). Factors potent
ially contributing to this mange outbreak include a mast crop failure in th
e fall of 1998 and transmission of mites from animal to animal during trapp
ing and processing sessions.