A Comparison of Methods for Studying Life History in Columbian Ground Squirrels

1986 ◽  
Vol 67 (1) ◽  
pp. 154-158 ◽  
Author(s):  
F. S. Dobson ◽  
R. M. Zammuto ◽  
J. O. Murie
Keyword(s):  
Life History ◽  
Ground Squirrels ◽  
Comparison Of Methods ◽  
Columbian Ground Squirrels

The influence of food resources on life history in Columbian ground squirrels

1985 ◽  
Vol 63 (9) ◽  
pp. 2105-2109 ◽  
Author(s):  
F. Stephen Dobson ◽  
Julia D. Kjelgaard
Keyword(s):  
Body Weight ◽  
Life History ◽  
Litter Size ◽  
Life History Theory ◽  
Experimental Manipulation ◽  
Food Resources ◽  
Ground Squirrels ◽  
Life History Characteristics ◽  
Columbian Ground Squirrels ◽  
Two Populations

Life history characteristics were studied experimentally in Columbian ground squirrels (Spermophilus columbianus) at two elevations in the Rocky Mountains of southwestern Alberta, Canada, from 1981 to 1984. In two populations with supplemented food resources, survival of young increased, age at maturity of females decreased, litter size increased, and spring body weight increased in comparison with an initial unmanipulated period and with two populations monitored for reference. For individual ground squirrels, litter size and spring body weight increased under supplementation. Thus, life history characteristics exhibited phenotypically plastic responses to experimental manipulation of food resources. Life history patterns changed among natural ground squirrel populations at different elevations and these changes were likely due to changes in food resources. A general prediction of life history theory that reproductive effort should be highest in years favorable for juvenile survivorship was supported by the experimental results. The results did not support predictions from interspecific studies of changes in life history characteristics that scale to body weight.

scholarly journals Increasing returns in the life history of Columbian ground squirrels

1999 ◽  
Vol 68 (1) ◽  
pp. 73-86 ◽  
Author(s):  
F. Stephen Dobson ◽  
Thomas S. Risch ◽  
Jan O. Murie
Keyword(s):  
Life History ◽  
Ground Squirrels ◽  
Increasing Returns ◽  
History Of ◽  
Columbian Ground Squirrels

scholarly journals Subtle short-term physiological costs of an experimental augmentation of fleas in wild Columbian ground squirrels

2019 ◽  
Vol 222 (12) ◽  
pp. jeb203588
Author(s):  
Jeffrey D. Roth ◽  
F. Stephen Dobson ◽  
François Criscuolo ◽  
Pierre Uhlrich ◽  
Alexandre Zahariev ◽  
...  
Keyword(s):  
Ground Squirrels ◽  
Short Term ◽  
Columbian Ground Squirrels

Effect of climatic conditions on the annual activity and hibernation cycle of Richardson's ground squirrels and Columbian ground squirrels

1977 ◽  
Vol 55 (4) ◽  
pp. 693-703 ◽  
Author(s):  
Gail R. Michener
Keyword(s):  
Rocky Mountains ◽  
Climatic Conditions ◽  
Ground Squirrels ◽  
Active Season ◽  
Southern Alberta ◽  
Annual Activity ◽  
The Times ◽  
Columbian Ground Squirrels ◽  
Spring Emergence ◽  
Species Ecology

In 1975 and 1976 the times of spring emergence, breeding, and entry into hibernation were compared for Spermophilus richardsonii and S. columbianus in an area of sympatry in the foothills of the southern Alberta Rocky Mountains. Both species emerged earlier in 1976, which had a warmer than normal spring, than in 1975, which had a cooler than normal spring. In both years S. richardsonii emerged earlier than S. columbianus and remained active longer. Juvenile S. richardsonii entered hibernation when 17–20 weeks old whereas juvenile S. columbianus were 10–11 weeks old. Yearling S. richardsonii bred, whereas yearling S. columbianus did not. Breeding success affected the time of entry into hibernation but not the time of emergence from hibernation in the next spring. A possible relationship between the periodic arousals during hibernation and the emergence pattern of squirrels in spring is discussed. The significance of flexibility of spring emergence, length of the active season, and age at breeding to survival and species ecology is considered.

The effects of capital on an income breeder: evidence from female Columbian ground squirrels

2005 ◽  
Vol 83 (4) ◽  
pp. 546-552 ◽  
Author(s):  
David R Broussard ◽  
F Stephen Dobson ◽  
J O Murie
Keyword(s):  
Path Analysis ◽  
Observational Data ◽  
Life Histories ◽  
Reproductive Investment ◽  
Ground Squirrels ◽  
Initial Capital ◽  
Spermophilus Columbianus ◽  
Live Trapping ◽  
Investment In Reproduction ◽  
Columbian Ground Squirrels

To maximize fitness, organisms must optimally allocate resources to reproduction, daily metabolic maintenance, and survival. We examined multiple years of live-trapping and observational data from a known-aged population of female Columbian ground squirrels, Spermophilus columbianus (Ord, 1815), to determine the influences of stored resources and daily resource income on the reproductive investments of females. We predicted that because yearling females were not fully grown structurally while producing their first litter, they would rely exclusively on income for reproduction, while reproductive investment in older females (≥2 years of age) would be influenced by both stored resources (capital) and daily income. Results from path analysis indicated that both yearlings and older females were income breeders. However, initial capital indirectly influenced investment in reproduction of yearling and older females. Females with the greatest initial capital maintained high body masses while investing relatively more income in reproduction. By considering influences of both capital and income, important relationships can be revealed between these resources and their influence on life histories.

Variation in reproductive success of male and female Columbian ground squirrels (Urocitellus columbianus)

2012 ◽  
Vol 90 (6) ◽  
pp. 736-743 ◽  
Author(s):  
Philip H. Jones ◽  
Jeffrey L. Van Zant ◽  
F. Stephen Dobson
Keyword(s):  
Reproductive Success ◽  
Mating System ◽  
Multiple Paternity ◽  
Ground Squirrels ◽  
Male Reproductive Success ◽  
Offspring Production ◽  
Bateman Gradient ◽  
Coefficients Of Variation ◽  
Males And Females ◽  
Columbian Ground Squirrels

The imbalanced reproductive success of polygynous mammals results in sexual selection on male traits like body size. Males and females might have more balanced reproductive success under polygynandry, where both sexes mate multiply. Using 4 years of microsatellite DNA analyses of paternity and known maternity, we investigated variation in reproductive success of Columbian ground squirrels, Urocitellus columbianus (Ord, 1815); a species with multiple mating by both sexes and multiple paternity of litters. We asked whether male reproductive success was more variable than that of females under this mating system. The overall percentage of confirmed paternity was 61.4% of 339 offspring. The mean rate of multiple paternity in litters with known fathers was 72.4% (n = 29 litters). Estimated mean reproductive success of males (10.27 offspring) was about thrice that of females (3.11 offspring). Even after this difference was taken into account statistically, males were about three times as variable in reproductive success as females (coefficients of variation = 77.84% and 26.74%, respectively). The Bateman gradient (regression slope of offspring production on number of successful mates) was significantly greater for males (βM = 1.44) than females (βF = 0.28). Thus, under a polygynandrous mating system, males exhibited greater variation in reproductive success than females.

Sign in / Sign up

Export Citation Format

Share Document