Geology topics

Marsha A. Sovada

Publications and source records attributed to Marsha A. Sovada.

21 records · Page 2Linked to original sources

USGS1999

An improved method for determining the distribution of swift fox in Kansas

During 1997 and 1998 we tested a new method for determining the distribution of swift foxes ( Vulpes velox ) in Kansas. From a sampling frame of 30 counties in western Kansas, we selected a systematic sample of alternate townships in a checkerboard pattern. During September and October 1997 and August 1998, experienced observers delineated suitable swift fox habitat within each sample township and searched it for evidence of occupancy (tracks, dens, and the animals themselves) by swift fox and other furbearers. Each township was searched for a minimum of 30 minutes, with searches continuing until swift foxes were either detected or for 120 minutes. Of the 288 townships selected in 1997, 271 (94.1%) were searched effectively with swift fox detected in 40.5% of the townships. Adverse weather conditions prevented surveys in two northwestern counties of our sample frame. In 1998, 245 township were searched effectively. Swift fox were detected in 27 counties searched to date. We did not detect swift fox in Seward, Meade and Ford counties, where the species is thought to be uncommon or absent. Tracks were difficult to discern in areas with hard or sandy soils and were sometimes obliterated by adverse weather, vehicle traffic, and agricultural activities. To determine how frequently we failed to detect swift foxes that were present, we plan to repeat searches in 1999 in townships where swift foxes were not detected previously. Nevertheless, preliminary results suggest our method to be a practical means for conducting landscape-scale presence/absence surveys of swift fox. Restricting searches to habitat judged best for swift foxes and most favorable for track detection helped control costs and achieve high detection rates.

Kansas↗

USGS1998

Population trends for common prairie pothole carnivores

Since settlement of the prairie pothole region of the northern Great Plains by Europeans in the late 1800’s, carnivore populations have changed considerably—mostly due to habitat alteration and humaninflicted mortality. At least 19 species of carnivorous mammals once occurred in the prairie pothole region (Jones et al. 1983). Presently, only eight are common throughout the region—coyote, red fox, raccoon, American badger, striped skunk, mink, ermine, and long-tailed weasel (Sargeant et al. 1993). Other species that occur locally or intermittently are mountain lion, lynx, bobcat, gray wolf, gray fox, swift fox, spotted skunk, and least weasel. Grizzly bears, wolverines, and river otters once occurred in the region but are now extirpated. Competition among species affects the distribution of coyotes, wolves, and foxes (Carbyn 1982; Rudzinski et al. 1982; Sargeant et al. 1987; Bailey 1992). These larger canids are keystone species that suppress the distribution of smaller canids (Johnson and Sargeant 1977; Dekker 1989; Johnson et al. 1989).

Book chapter↗

USGS1995

Differential effects of coyotes and red foxes on duck nest success

Low recruitment rates prevail among ducks in the Prairie Pothole Region of North America, primarily because of high nest depredation rates. The red fox (Vulpes vulpes) is a major predator of duck eggs, but fox abundance is depressed by coyotes (Canis latrans). We tested the hypothesis that nest success of upland-nesting ducks is higher in areas with coyotes than in areas with red foxes. We conducted the study during 1990-92 in uplands of 36 areas managed for nesting ducks in North Dakota and South Dakota. Overall nest success averaged 32% (95% CI = 25-40) on 17 study areas where coyotes were the principal canid and 17% (CI = 11-25) on 13 study areas where red foxes were the principal canid (P = 0.01). Both canids were common on 6 other areas, where nest success averaged 25% (CI = 13-47). Habitat composition, predator communities with the exception of canids, and species composition of duck nests in coyote and red fox areas were similar overall. Upon examining only nests with greater than or equal to 6 eggs on the last visit prior to hatch or depredation, we determined nests with evidence characteristic of fox predation accounted for 4% of depredated nests in coyote areas and 27% in fox areas (P = 0.001). An expanding coyote population is contributing to higher overall nest success. Management of coyotes may be an effective method for increasing duck nest success.

North Dakota; South Dakota↗