Graduation date: 2008The potential for Rocky Mountain mule deer (Odocoileus hemionus hemionus) to host exotic chewing lice (Damalinia (Cervicola) sp.) believed to cause deer hair loss syndrome in Columbian black-tailed deer (Odocoileus hemionus columbianus), was investigated in captive deer held in pens at E.E. Wilson Wildlife Area, Corvallis, Oregon from March 2004 to May 2005. It is believed that the exotic chewing louse causes a hypersensitivity reaction which results in pruritis, excessive grooming and removal of pelage. The potential transmission of D. (Cervicola) sp. from affected black-tailed deer to Rocky Mountain mule deer (Odocoileus hemionus hemionus) was unknown. To answer this question, unaffected mule deer were both experimentally infested (inoculated) with D. (Cervicola) sp., and held in direct contact with (D. (Cervicola) sp.) infested black-tailed deer. Grooming behavior, louse abundance, and clinical signs were monitored and recorded monthly for 14 months. The exotic louse D. (Cervicola) sp. was identified on six mule deer following treatment, and evidence of louse reproduction (eggs, and nymphs) was present. A strong seasonal pattern in louse abundance was observed in all groups and within subspecies, and was correlated with date, with higher louse abundances occurring from April-June 2004, and March- May 2005; lower numbers occurred from August 2004 through February 2005. Eggs, nymphs and adult lice were found on all body regions, and abundances varied by month. Mule deer held in direct contact with infested black-tailed deer showed slight increases in frequency of grooming behavior from January to April 2005 in conjunction with increasing louse abundance and grooming bout duration. Six mule deer developed small localized patches of hair-loss following treatment; two had hair loss throughout much of their sides and rump. Eight black-tailed deer showed signs of recovery at the end of the study. It was concluded that transmission of the exotic louse D. (Cervicola) sp. from infested black-tailed deer to non-infested mule deer is possible when the two species are held in direct contact. In addition, there is a link between the irritations caused by the infestation of D. (Cervicola) sp.; grooming response; and loss of hair in both black-tailed deer and mule deer.