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Columbia Ground Squirrel in Subalpine Forest Openings in Central Idaho Item Type text; Article Authors Lambeth, R.; Hironaka, M. Citation Lambeth, R., & Hironaka, M. (1982). Columbia ground squirrel in subalpine forest openings in central Idaho. Journal of Range Management, 35(4), 493-497. DOI 10.2307/3898613 Publisher Society for Range Management Journal Journal of Range Management Rights Copyright © Society for Range Management. Download date 02/10/2021 06:26:48 Item License http://rightsstatements.org/vocab/InC/1.0/ Version Final published version Link to Item http://hdl.handle.net/10150/645976 Columbia Ground Squirrel in Subalpine Forest Openings in Central Idaho RON LAMBETH AND M. HIRONAKA Abstract Columbia ground squirrels were studied in natural alpine forest Annual precipitation, mostly in the form of snow, ranges from openings. Three sites were selected having the same potential but 635 mm to more than 1400 mm (25 to 55 in.). Sporadic, high presently with different vegetation due to differing levels of past intensity, short duration summer thunderstorms are moderately domestic sheep use. Ground squirrel population was least in the frequent. The growing season is less than 60 days at 1800 m (6000 light-use area and increased with vegetation change induced by ft), while frost may occur any night during the summer. increased sheep use. Juveniles were most plentiful in the medium- The short growing season, the coarse plant material and youth- use site and least in the heavy-use area. Up to a point, ground fulness of the geomorphology have restricted soil development. squirrel population increased with plant retrogression. With con- Entisols and Inceptisols dominate. tinued retrogression the community became less suitable to sup The extreme climatic and elevational gradients are responsible port a healthy population because of less preferred forage species. for the numerous vegetational zones in the Idaho batholith. At the Lupinus sericeus was the most preferred forb. Other species lower elevations, true Palouse bunchgrass occurs. With increasing included Achilles millefolium and Descurania richardsonii, spe- elevation, the vegetational series encountered are ponderosa pine, cies not generally preferred by sheep. The discussion of sheep- Douglas-fir, grand fir, Engelmann spruce-fir, and the subalpine ground squirrel relative impacts also considers metabolic fir-whitebark pine (Daubenmire 1970, Evans and Tisdale 1972, requirement, grazing. period and animal density of both grazers. Steele et al. 1975). Eighty percent of the batholith is coniferous forest. The subalpine fir-whitebark pine zone is relatively small in Natural forest openings in the subalpine zone provide the bulk of total area yet is of primary importance for sheep summer range. the forage on domestic sheep summer range in central Idaho. In Applicability of research findings to other areas of the batholith these openings Columbia ground squirrels (Citehs cohmbianus) was a prime consideration in selection of study area. are readily observed as they forage and sit up near burrow entran- ces, quietly observing their surroundings and darting into the Methods safety of the burrow when alarmed by unfamiliar sound or move- ment. The foraging activity is confined to daylight hours during the The study was conducted in forest openings associated with the growing season. Depending on locality, these animals hibernate subalpine fir-whitebark pine series at about the 2275 m (7500 ft) for 7 or 8 months (Shaw 1926). The adult ground squirrel weighs MSL. Three openings were selected on the basis of known sheep about a pound (450 g), with males outweighing females. grazing histories, i.e., lightly used, heavily used bedding ground Observations suggest that the Columbia ground squirrel com- and a moderately utilized opening. The historic use was not mea- petes for the same forage utilized by domestic sheep on the summer sured, but was determined through communication with U.S. range. Other studies have indicated that ground squirrel popula- Forest Service personnel. In the year of study there was no grazing tions increase with livestock grazing primarily because changes in by sheep. The medium and heavy-use areas generally had been composition and structure of the vegetation provide greater visibil- grazed every year and the light-use area one year in two. All three ity for the small animal (Smith 1940, Howard and Childs 1959). sites were in the same grazing allotment. All sites were southerly Because of the importance of the subalpine forest openings for exposed with slopes ranging from 12 to 38% and with similar domestic sheep grazing and the association of these openings to the granitic parent material. The original vegetation was thus judged Columbia ground squirrel, it is important that the interrelation- to be essentially the same for the three sites. ships are better understood. The purpose of this study was to At each site, two contiguous 50 X 50 m (165 X 165 ft) plots were determine the diet of the Columbia ground squirrel, its effect(s) on delineated. One of the two plots was randomly selected for inten- sive vegetation sampling. The other was used for live trapping of plant communities and population response in relation to domestic sheep grazing. ground squirrels. Vegetation Sampling Area of Study Vegetation was sampled for foliage cover by species as deter- mined by a vertical IO-point frame (Goodall 1952) with 50 random The study was conducted in the Idaho batholith portion of the placements at each of the three sites. Sampling was done in July at Payette National Forest in central Idaho. This batholith is the the peak flowering of the most species. Yield was determined by largest granitic intrusion in the United States and occupies nearly individual species in ten .lOm* (.96 ft2) randomly located plots. 16,000 square miles. The terrain is extremely rugged, with uplifting Yield is reported as oven-dried (7OOC). and faulting and mountain glaciation determining the land con- Ground Squirrel Sampling tour. Long, steep-flanked ridges with occasional peaks character- Columbia ground squirrel population data were gathered from ize this mountainous area. Elevational extremes range from 550 m 10 X 10 X 40 cm (4 X 4 X 16 in.) live traps placed in a grid pattern of (1800 ft) MSL to peaks of 2725 m (9000 ft) MSL (Thompson 1973). 3 across the plot by 4 down, making 12 traps per plot. Traps were R. Lambeth is presently with the Bureau of Land Management, Grand Junction, operated for a 24-hour period before removal to another site. The Colorado. same site was resampled every third day. The traps were checked This paper is published with the approval of the Director, Forest, Wildlife, and Range Experiment Station, University of Idaho, Moscow 83843, as Contribution No. twice daily, noon and sunset. All capture points were mapped. 236. This study was supported in part from M&tire-Stennis funds. Manuscript received November 17. 1980. JOURNAL OF RANGE MANAGEMENT 35(4), July 1982 493 Captured squirrels were removed to a handling cone, sexed, Lightly Used Medially Used Heavily Used weighed, marked with black hair dye on adults and 5% picric acid solution on juveniles(young of the year), and then released. Recap- tured animals were weighed and, if needed, the markings were refreshed before release. Fecal pellets in traps were collected and -: 36 species 39 species ::. 34 Sp.Cle‘ salted for preservation. Fecal samples of adults were composited H - 3.95 Ii = 319 b’.’ Ii = 2.35 358 k!j/ho 389 kg/ha .:.:: 369 kg/ho daily by site; those of juveniles constituted a separate sample. At ., the end of the population sampling, ten individuals were sacrificed for stomach and colon content comparison. This was to test the reliability of the microscopic fecal analysis that was to be made later. The trapping period was from July 17 to August 21 and again on September 7. Reference plant material for microscopic fecal analysis was collected. Dietary Analysis :,:: The microscopic technique of diet analysis is well known 7 (Brusven and Mulkern 1960, Storr 1961, Sanders et al. 1980). Microscopic slides were prepared from identified reference plants I:‘: in the manner described by Cavender and Hansen (1970). <I -10 2498 <I Cl 4-10 24-46 The Wiley mill was used to grind fecal and stomach samples to l-3 ‘I l-23 ;49-97 l-3 I l-23 4997 l-3 II-23 49-97 be analyzed. Reference plant materials were also ground in the Cover 1%) class Intervals Cover P/J class mtervols Cover (%I close intervals Wiley mill to make them of uniform particle size with that in the fecal and stomach samples. From this material 8 mgaliquants were Fig. 1. Number of species present in different cover classes (increasing by Log:), total yield and Shannon- Weaver Diversity Index (IY) of 3 subal- taken for quantitative reference slides. For each of these reference pine forest opening communities with dlyferent past levels of domestic plant species there was a known weight of material spread over a sheep use. The number of grass and grasslike species are given in the standard area the size of the cover of glass. Quantitative reference stippled area of the columns; the number forbs are presented in the slides were made separately for the floral and leaf parts of most unstippled area. species. The type of epidermal tissue fragment selected as diagnostic for lightly grazed and the heavily grazed sites, placing them at each species appeared on the respective quantitative reference extremes to each other. Following the descending diversity indices slides in the frequency range of 45-75 percent of the observed for the plant communities, the three sites move down the succes- microscope tields. Frequencies were converted to density values sional gradient from the lightly grazed to the medially grazed to the expected under random conditions according to Fracker and Bri- heavily grazed field.

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