Great Basin Naturalist


We samp led both subspecies of the Idaho ground squirrel (Spermophilus brunneus) to document the larger ectoparasites of this rare endemic. S. b. brunneus was host (+ = new host record, * = new Idaho record) to 4 flea species (Neopsylla inopina+, Oropsylla idahoensis+, O. tuberculata, and Thrassis pandorae+), 1 tick (Ixodes sculptus+), and an eyeworm (Nematoda: Rhabditis orbitalis*+, also 1st records from Seiuridae); S. b. endemicus was host to a louse species (Neohaematopinus laeviusculus+), 5 flea taxa (Rhadinopsylla sp.+, O. t. tuberculata, Thrassis f. francisi+, T. f. barnest+, and T. f. rockwoodi), and a mite (Androlaelaps fahrenholzi+). Spermophilus brunneus had fewer known ectoparasite species than other congeners. Although all of their parasites had many other hosts, S. b. endemicus and S. b. brunneus shared only a single parasite species in common, whereas all but one of their ectoparasites also occurred on the closely related Townsend's ground squirrel (S. townsendii). The proportion of parasitized individuals and the parasite loads per individual were significantly lower in S. b. brunneus, which lives in small, isolated populations, than in S. b. endemicus, which has larger, less fragmented populations, suggesting a relationship between host population structure, parasite loads, and parasite species diversity. All but one of the flea species have been linked to plague transmission.