Lungworm Infections, Reproduction and Summer Habitat Use of Bighorn Sheep in Custer State Park, South Dakota

Bighorn sheep (Ovis canadensis) were once indigenous to the Black Hills and Badlands of South Dakota. When European settlers moved into this region during the late 1800\u27 s, market hunting, loss of habitat, and introduction of animal diseases and parasites caused the subspecies of the region, the Audubon\u27s bighorn sheep (O. c. auduboni), to become extinct by 1916 (Buechner 1960). To reestablish bighorn sheep in the Black Hills, 8 Rocky Mountain bighorn sheep (O. c. canadensis) were introduced into the former range of the Audubon\u27s sheep in 1922. Finding the habitat to be very suitable, this small population increased to about 150 animals. A suspected waterborn disease (leptospirosis?) decimated this population, causing it to decline to 1 animal by 1959 (W. Winter, Custer State Park, pers. comm.). A second reintroduction of Rocky Mountain bighorn sheep was made in Custer State Park in 1964. Again the population increased, reaching a level of 100-150 animals by 1975 (Trefethen 1975). The population in the park has failed to increase above this 1975 level, having at present an estimated population of 120 animals. Two possible factors are limiting the expansion of the herd: 1) mortality induced by a lungworm-pneumonia complex (Spraker 1981, Hibler et al. 1972, Forrester 1971), and/or 2) carrying capacity restricted by some habitat factor. Previous studies have indicated that the Custer State Park bighorn herd is infected with the lungworm Muellerius capillaris (Pybus and Shave 1984). However, very little is known of the reproductive success of the herd or of the behavior and habitat use of the sheep. To ascertain whether parasitic influence and/or habitat availability are instrumental in negating population growth, close examination of the level of lungworm infection, reproductive success, and habitat use of the bighorn sheep in the park was necessary. Only with this information can Custer State Park meet the management objective of maintaining a healthy bighorn sheep herd for both the viewing and sporting public

Bed Site Selection of Fawn Pronghorn in Custer State Park, South Dakota

We evaluated pronghorn (Antilocapra americana) fawn bedding site characteristics on a prairie and ponderosa pine (Pinus ponderosa) landscape interface in Custer State Park, South Dakota. We radio-marked 16 adult female pronghorn and collected bed site information from their fawns during 2007~2008. We compared bed site selection with random sites (n = 74) during 2 periods; the early hiding phase when fawns were 1 ~28 days of age (n = 23 bed sites) and the later group phase when fawns were 29~60 days of age (n = 52 bed sites). During the hiding phase fawns selected dry prairie-seminatural mixed grassland at the course-scale level; group phase fawns selected prairie dog (Cynomys ludoviciana) dominated grasslands and dry prairie-seminatural mixed grassland at the course-scale. Evaluation at the fine-scale indicated fawns during the group phase period selected bed sites that had greater forb cover and overs tory canopy cover of ponderosa pine trees compared to random sites. Management activities that promote a dynamic grassland ecosystem with patches of forb cover may enhance resources selected as bedding habitat by pronghorn fawns during the group phase period