Patterns of seasonal activity and host-parasite relationships for fleas associated with Richardson's ground squirrels, Spermophilus richardsonii, in southern Manitoba, Canada

Abstract

The host-parasite relationships between several flea species and their host, Richardson's ground squirrel, Spermophilus richardsonii (Sabine), were evaluated at three localities in Manitoba during a three year study. Ground sguirrels captured near Darlingford, Manitoba were infested with Neopsylla inopina (Rothschild), Opisocrostis bruneri (Baker), Oropsylla rupestris (Jordan) and Rhadinopsylla fraterna (Baker). Opisocrostis bruneri was the only one of these species infesting squirrels at the two sites near Winnipeg, Manitoba (designated Perimeter and St. Norbert). Adult ground squirrels emerged during late March and early April, males approximately seven days before females. Juveniles first appeared above ground in late May and early June. Adult male sguirrels immerged to hibernate from mid-June to early July; adult females from late July to mid-August; female juveniles before male juveniles. The last juveniles were captured in early September to mid-October. AT Darlingford, 268 individual squirrels were captured 2308 times during 1987-1989. At the two sites near Winnipeg, 184 individuals were captured 1689 times during the same period. Juvenile squirrels constituted 64.7% to 92.9% of the total captures and were the most frequently recaptured stage in 1987 and 1988. At Darlingford, 1,446 N. inopina, 4,657 O. bruneri, 12,506 O. rupestris and 379 R. fraterna were taken from S. richardsonii during 1987-1989. At the two sites near Winnipeg, 6,212 O. bruneri were collected from squirrels during the same period. Female fleas were usually collected more often than males for all flea species and the observed biweekly sex ratio (M/F) generally favoured females for all flea species. With the exception of two weeks in April, N. inopina was present on less than 50% of the squirrels. There was one peak in observed mean intensity in April during 1988 and 1989. There were two peaks of prevalence and mean intensity for O. bruneri during May and August at Darlingford and near Winnipeg. During early April, early July and September there were peaks in the prevalence and mean intensity of O. rupestris. The prevalence of R. fraterna adults on Richardson's ground squirrels was generally below 10% and squirrels were rarely infested with more than one or two R. fraterna adults, except during early April and from mid-August to the end of the trapping season...