Great Basin Naturalist Volume 49 Number 3 Article 14 7-31-1989 Influence of experimental habitat manipulations on a desert rodent population in southern Utah Jiping Zou Brigham Young University Jerran T. Flinders Brigham Young University Hal L. Black Brigham Young University Steven G. Whisenant Texas A&M University Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Zou, Jiping; Flinders, Jerran T.; Black, Hal L.; and Whisenant, Steven G. (1989) "Influence of experimental habitat manipulations on a desert rodent population in southern Utah," Great Basin Naturalist: Vol. 49 : No. 3 , Article 14. Available at: https://scholarsarchive.byu.edu/gbn/vol49/iss3/14 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. INFLUENCE OF EXPERIMENTAL HABITAT MANIPULATIONS ON A DESERT RODENT POPULATION IN SOUTHERN UTAH 1 2 4 JipingZou , JerranT. Flinders . Hal L. Black', and Steven G. Whisenant Abstract. —This paper addresses how habitat manipulations in a black sagebrush (Artemisia nova) -dominated area, John s Valley of southern Utah, affected resident desert rodent populations. Rodents studied included the deer mouse {Peromyscus maniculatus), Great Basin pocket mouse (Perognatkus partus), sagebrush vole (Lagurus curtatus), Ord's kangaroo rat (Dipodomys ordii), and least chipmunk (Eutamias minimus). The experimental design involved analyses of treatment and control (nontreatment) plots rather than pre- and posttreatment of all plots. Habitat manipulations emphasized cutting of shrubs (rotobeating), treatment of plants with a herbicide (2,4-D), and reseeding with a mixture of grasses, forbs, and shrubs. Posttreatment trapping indicated the deer mouse was the most abundant rodent in treatment and control plots. Data indicate the prescribed habitat treatments had no significant negative affects on the deer mouse demes on the control or treatment plots. Habitat treatments may have negatively impacted recruitment in pocket mice. Least chipmunks were not captured in plots treated by rotobeating. Our habitat manipulations may have contributed to interspecific competition in this rodent community through the reduction of both food and cover. Many ecological factors influence the dy- supplies and essential microhabitat (Taylor namics of a cold desert rodent population. 1963, Weckey 1963, Holbrook 1979). Alterna- When aspects of the vegetational habitat are tive conclusions resulting from Parmenter altered for management purposes, subse- and MacMahon's (1983) habitat manipulations quent responses can be expected in rodent within a shrub steppe ecosystem suggest that populations that reflect changes in inter- shrub architecture and other shrub-related specific relationships as well as changes in resources are unimportant to some rodents density, home range, reproduction, disper- (e.g., deer mouse, Peromyscus maniculatus, sal, recruitment, body size, and food habits. It Great Basin pocket mouse, Perognatkus is difficult to relate measured responses to parvus; and northern grasshopper mouse, specific changes of components in the habitat. Onychomys leucogaster). Others have shown Reason suggests an interrelated hierarchy of that the vertical and horizontal complexity of limiting factors operating either individually, foliage do not correlate well with functional in an additive fashion, or synergistically to diversity of small mammals (MacMahon 1976, elicit a series of responses from the impacted Grenat and Serranos 1982). rodent population. Johnson and Hansen (1969) found that Previous studies of critical factors suggest 2,4-D (2,4-dichlorophenoxy acetic acid) her- that bicide treatments did not eliminate cover pro- population density is a consequence of survival, repro- vided by stems and branches of shrubs killed duction, and dispersal of individuals. These processes by the treatment. They observed no signifi- are affected by the capacity to tolerate expressions of the physical environment, the availability of essential cant differences in deer mouse density be- resources and interactions with other individuals of the tween treated and untreated rangelands. same and different species (Brown and Munger 1985). The opportunity to further explore the rela- They have shown that limited food resources tionships between small rodents and distur- as well as interspecific competition within a bances in their habitats came as a companion guild of ecologically similar species play a ma- study of habitat alterations designed to benefit jor role in regulating the density of desert the Utah prairie dog (Cynomys parvidens), a rodent populations. threatened species (U.S. Fish and Wildlife Other studies have indicated that habitat Service, 49CFR2330). This suite of habitat- manipulations adversely affect rodent food disturbing treatments, along with control Department of Botany and Range Science, Brigham Young University, Provo, Utah 84602. Wildlife and Range Resources Laboratory, 407 WIDB, Brigham Young University, Provo, Utah S4602. ^Department of Zoology. 167 WIDB, Brigham Young University, Provo, Utah 84602. ^Department of Range Science, Texas A&M University, College Station, Texas 77843. 435 436 Great Basin Naturalist Vol. 49, No. 3 200 cd c o 00 -100 2 o Q. Q. O E CD H Fig. 1. Climatic diagram representing weather variables (temperature, C; precipitation, mm) measured at Bryce Canyon, Utah, during 1986. areas, allowed examination and testing of the tional cold desert shrubland. Dispersion of following hypotheses relating to small mam- vegetation varies from open grassy areas to mals (excluding C. parvidens): stands of closely or widely spaced shrubs. 1. Population densities of small rodents on treated plots Dominant shrubs in this area are black sage- would be reduced by a combination of factors includ- brush {Artemisia nova), fringed sagebrush ing depressed reproduction, increased dispersal, and (Artemisia frigida), carpet phlox (Phlox increased mortality. hoodii), dwarf rabbitbrush (Chrysothamnus 2. The size of home ranges of the various rodent species depressus), rubber rabbitbrush (Chryso- would generally increase on treated areas. thamnus nauseosus), winterfat (Ceratoides 3. indicator of body condi- Body weights of rodents, as an lanata), and broom snakeweed (Gutierrezia tion, would be proportionately less on treated plots. sarothrae). Dominant grasses are western 4. species would decrease in rela- Diversity of rodent wheatgrass (Agropyron smithii) and squirrel- tionship to vegetational treatments; interspecific tail (Elymus elymoides). Prominent forbs are dominance by one or more species may be evidenced. pretty rockcress (Arahis pulchra), vernal 5. The effects of vegetational treatments can be quantita- daisy (Erigeron pumilus), and longleaf phlox tively measured and expressed in ways meaningful to resident rodent populations. (Phlox longifolia). Scientific names of plants are after Welsh et al.(1987). Average monthly precipitation was 39 in 1986 but is highly Study Area and Methods mm variable (0 to 130 mm) from month to month. The study site (2.56 square km) is just west The wettest months of the year are from July of Widtsoe Junction, Garfield County, near to September. Mean monthly temperatures Bryce Canyon National Park. It was estab- range from —2 C in January to 17 C in July lished on lands administered by the state of (Fig. 1). Utah in what is known as John's Valley. The Studies were conducted on 12 plots, average elevation at the study site is 2,290 m, each 165 x 165 m and located at least 0. 16 km and, although the terrain is relatively flat, the from adjacent plots. The experimental design northeast corner is dissected by a dry water- represented a randomized complete block course. Vegetation is primarily upper eleva- with three replications. Three treatments July 1989 Zou etal.: Rodent Habitat Manipulations 437 Fig. 2. The location of the study site in southern Utah and the spatial relationship of the treatment and control plots. (September and October 1985) included (1) Each plot contained a 10 x 10 station trap- mechanical shredding (rotobeating) followed ping grid with each trap 10 m apart; thus, 100 by reseeding; (2) spraying with 3.3 kg/ha live-capture traps (38 x 11 x 11 cm) were 2,4-D (2,4-dichlorophenoxy acetic acid) per monitored in every plot each day of trapping. plot; and (3) spraying with 3.3 kg/ha 2,4-D per Trap stations were permanently marked with plot followed by reseeding (Fig. 2). The 12 a numbered stake. Traps were set on each plot study plots were divided into three blocks for five consecutive nights during three trap- with three treatment plots and one control ping periods (5-23 May, 23 June-11 July, plot in each block. All treated plots were en- 4-22 August 1986). Traps were baited with a closed with electrical wire fencing in May grain mixture after 6 p.m. and checked before 1986 to prevent grazing by livestock. 9 a.m. the next morning. This time interval 438 Great Basin Naturalist Vol. 49, No. 3 allowed capture of diurnal as well as nocturnal Population dynamics of the deer mouse, rodents. Trapped mammals were identified pocket mouse, and other rodents were inves- and checked for sex, age (adult or juvenile), tigated between May and August 1986. Home weight, reproductive condition, and station range