Time Budgets of Wyoming Ground Squirrels, Spermophilus Elegans
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Great Basin Naturalist Volume 41 Number 2 Article 9 6-30-1981 Time budgets of Wyoming ground squirrels, Spermophilus elegans David A. Zegers University of Colorado, Boulder Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Zegers, David A. (1981) "Time budgets of Wyoming ground squirrels, Spermophilus elegans," Great Basin Naturalist: Vol. 41 : No. 2 , Article 9. Available at: https://scholarsarchive.byu.edu/gbn/vol41/iss2/9 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]. TIME BUDGETS OF WYOMING GROUND SQUIRRELS, SPERMOPHILUS ELEGANS David A. Zegers' .\bstract.— Time budget of free-living adult Spermophiltts elegans differed significantly from that of juveniles in the Front Range of the Rockies during 1974-1975. No differences were found between males and females. Hour of day. day since emergence, air temperature, cloud cover, and presence of predators all correlated with the frequency of various components of the time budget. Study of time budgets is important in com- binocular, and a 20X telescope to observe the prehending the roles of animals in ecosystems squirrels from a blind. The animals were as well as understanding their basic patterns marked for individual recognition from a dis- of behavior. Time budgets constructed for a tance using a unique combination of freeze few ground .squirrels [the Columbian ground brands (Hadow 1972) located at one or two squirrel, Spemiophihis columbianus (Betts of the spots on the animal's body. 1976); the thirteen-lined ground squirrel, S. The behavior of these ground squirrels was tridecemlineatus, and the spotted ground divided into 13 categories (i.e., activities) (Ze- .squirrel, S. (Streubel spilosoma 1975); and gers 1977). This classification scheme is sim- Belding ground squirrel, S. belding (Morton ilar to those previously used for this squirrel 1975)] illu.strate the .significant effects exo- (Clark and Denniston 1970) and for the close- genous factors and endogenous have on the ly related Richard.son's ground squirrel, S. time allotted to various activities. My objec- richardsonii (Quanstrom 1968 and 1971). tives were (1) to produce time budgets for These 13 activities and their definitions are the Wyoming ground squirrel, Spennophihis as follows: elegans {sensu Nadler, Hoffmann, and Greer 1. The basic posture is a resting and observation posi- 1971; (2) to document differences in time tion with all four paws on the ground. budgets due to age and sex; (3) to correlate 2. Semi-alert posture is a resting and observation posi- variation in time budget with several envi- tion in which the forepaws are off the ground and ronmental factors: weather, day since emer- the back is arched. gence, hour of day, and presence of pre- 3. The alert position is a resting and observation posi- tion in which the forepaws are off the ground and dators; and (4) to assess the ecological and the back is straight, not arched. evolutionary correlates of these variations in 4. The down feeding posture is a variation of the basic time budget. posture in which the squirrel is eating. Food is ma- nipulated using the teeth and lips without the aid of the forepaws. Methods 5. The upright feeding posture is a variation of either the semi-alert or alert postures in which food is han- A colony of free-ranging Wyoming ground dled with the forepaws. squirrels was observed from 18 May 1974 to 6. Running is a rapid locomotor activity in which the 24 August 1974 and from 20 April 1975 to 20 animal is moving > 1.0 m/s and is not involved in a chase. August 1975 in a montane meadow (2440 m 7. Chasing is running in which the individual is chas- elevation) in the Front Range of the Rocky ing another. Mountains approximately 16 km southwest of 8. Chased is running in which the individual is being Boulder, Colorado (Zegers and Williams chased. 1979). 9. Walking is relatively slow (compared to running) lo- comotion of < 1.0 m/s. Using the technique of Wiens et al. (1970), 10. Hay-gathering involves stuffing herbaceous stems I employed an electronic metronome. and leaves into the mouth without chewing and 'Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder, Colorado 80309. Present address: Department of Biology, Millersville State College, Millersville, Pennsylvania 17551. 221 222 Great Basin Naturalist Vol. 41, No. 2 swallowing. These materials are cut or pulled up by Few time budgets of other sciurids are of the forepaws and teeth and placed in the use available for comparison. Betts (1976) found mouth perpendicular to the sagittal line and then that feeding consumed from 49 to 86 per- deposited somewhere underground. 11. Grooming includes self- and allogrooming as well as cent, and "alertness" occupied from 6 to 26 dusting, in which a squirrel rolls from side to side percent of the total time above ground of while prostrate in the dirt of an entrance mound. Spermophilus cohimbianus. Tamiasciunis, 12. Digging is the behavior in which a squirrel removes the red squirrel, spent approximately .35 per- soil from a tunnel entrance by using either or both hind limbs and forelimbs. cent of its total time above ground feeding, 13. Fighting is similar to fighting among other rodents, although this percentage ranged from 9 to 60 and involves rolling, biting, clawing, and yelping. percent (Smith 1968). Streubel (1975) found Spermophilus tridecemlineotiis spent 42.4 Other data were collected for each of 1125 percent and S. spilosoma spent 45.6 percent observation periods, which lasted from 5 to of its time feeding, but only 11.6 percent and 15 minutes. These data included date, time of 15 percent, respectively, in some alert pos- observations, animal identification number, tures. Sexual and agonistic behavior com information about predators (i.e., whether or prised less than 5 percent of the total budget not a predator was visible, and, if so, its spe- for these species. When above ground, cies), and weather conditions. Air temper- Wyoming ground squirrels spent a smaller ature was measured at 0.5 m above ground proportion of their time feeding, and more every half hour. Sky cover was divided into time in sedentary observation than these four cloud categories: clear (no clouds), part- other species. This may be due to a greater ly cloudy (less than 50 percent of sky cov- predators, or to prevailing habi- ered), mostly cloudy (more than 50 percent threat from differences in so- of sky covered) and overca,st (complete cloud tat conditions resulting in cover). cial system or foraging strategy. Differences in time budget due to age and These differences in time budget also re- sex were tested via chi-square analysis. The flect differences in territorial maintenance relationship between five environmental fac- strategy. For example, Tamiasciunis, a squir- tors and the components of time budget were rel that defends a food supply, uses a strategy analyzed by multiple regression. Air temper- that spends little time on actual territorial ature, day since emergence, hours of day, sky defense (0.25 to 1.85 percent of active time. conditions, and presence of predators served Smith 1968). Complete defense is probably as independent variables, and the frequencies difficult if not impossible in the spatial com- of each of the 13 activities for each of the ob- plexity of the coniferous forest. It appears to servation periods were the dependent be energetically adaptive to use warning calls variables. and to tolerate some intrusion rather than to spend considerable time and energy chasing other squirrels. Spermophilus spilosoma and FIesults and Discussion S. tridecemlineatus do not defend food sup- plies. Their territoriality can be described as Although the behavior of S. elegans has core monopolization (Streubel 1975), in been studied (Clark 1970a, Clark and Dennis- which individual distance and the tendency ton 1970, Pfeifer 1980), a time budget has to remain near the home burrow spaces indi- never before been constructed. Aboveground viduals. No cooperative or extended familiar time budget for all individuals is shown in behavior and little agonistic behavior occur Figure 1. Note that the two feeding activities (Streubel 1975). In contrast, S. richardsonii were the most protracted, combining to con- and S. elegans do not defend food territories sume 39.3 percent of all time spent above but do defend reproductive territories. Dur- ground. The three sedentary but watchful po- ing mating individual males occupy terri- sitions (basic, semi-alert, and alert) were the tories that contain the home ranges of several next most frequent, followed by the five pos- females (Yeaton 1972). These are succeeded tures labeled "individual maintenance." Note by female territories during gestation and that the three agonistic activities were the lactation (Quanstrom 1968, Yeaton 1972). My least frequent. observation of female territories for S. June 1981 Zegers: Wyoming Ground Squirrels 223 35r 30 25 oUJ z K 20 (T O o I- z 15 oUl cr UJ a. 10 i i i m. ^ t^ i M UJ CD CD £C Z I- CD q: h- O o o I- o UJ ^ z o ILJ K o X UJ X 5 CO CD 3 < UJ Q. S2 CO o q: < < i 5 < CD < Q. X CD < CD o cr GQ X I a: O UJ 3 o Li_ ^ UJ O o CD X o I- X o zCD << o <UJZ UJ UJ QZ OiijUJ> POSTURE Fig. 1. Time budget of a population of Wyoming ground squirrels during the summers of 1974 and 1975.