Territoriality and dominance in male Columbian ground squirrels (Spermophilus columbianus)

1978 ◽  
Vol 56 (11) ◽  
pp. 2402-2412 ◽  
Author(s):  
J. O. Murie ◽  
M. A. Harris
Keyword(s):  
Aggressive Behavior ◽  
Ground Squirrels ◽  
Adult Males ◽  
Length Of Residence ◽  
Visual Contact ◽  
Habitat Features ◽  
Spermophilus Columbianus ◽  
Core Areas ◽  
Columbian Ground Squirrels ◽  
Spacing System

We describe the spacing system and associated aggressive behavior of male Columbian ground squirrels in southwestern Alberta for the 2 months following emergence from hibernation. Adult males (> 2 years old) were classified as dominant if they chased other males more than they were chased by them within their core areas and subordinate if the reverse was true. For dominant males, the proportion of interactions in which they were chased was much less within their core areas than outside them, and defended boundaries between some pairs of adjacent males were apparent from locations of chases and chase reversals. We consider these males to maintain spatiotemporal territories. For subordinate males, the proportion of interactions in which they were chased was similar inside and outside their core areas; they were subordinate in most interactions with any territorial male. Status (dominant–territorial or subordinate) was related to age. Most 2- and 3-year-old males were subordinate; all males of 4 years or older were territorial. Among different groups of male Columbian ground squirrels, variation in expression of the spacing system may depend on habitat features that affect visual contact among squirrels and age and length of residence of the males in the area.

The proximate causes of male-biased natal emigration in Columbian ground squirrels

1993 ◽  
Vol 71 (1) ◽  
pp. 204-218 ◽  
Author(s):  
Darwin R. Wiggett ◽  
David A. Boag
Keyword(s):  
Ground Squirrels ◽  
Home Ranges ◽  
Adult Males ◽  
Spermophilus Columbianus ◽  
Adult Females ◽  
Study Support ◽  
Proximate Causes ◽  
Natal Home ◽  
And Behavior ◽  
Columbian Ground Squirrels

The results of this study support the hypothesis that male-biased emigration of yearling male Columbian ground squirrels (Spermophilus columbianus) is socially induced. The likelihood of emigration from both the natal site and the natal colony was correlated with parameters of social structure and behavior. Agonism by the mother and (or) neighboring adult females, in association with parturition and lactation, apparently caused the initial shifts of yearling males away from their natal home ranges. After these shifts, yearling males that lived in areas where the number of neighboring males (both adult and yearling) was high relative to the number of females emigrated to areas within the natal colony that were more female-biased (intracolony emigration), or emigrated from the natal colony (intercolony emigration). Reduced numbers of adult males apparently resulted in lower rates of emigration by yearling males. Among the latter, emigrants appeared to be subordinate to non-emigrants. We discuss these findings in light of current hypotheses concerning the proximate and ultimate causes of emigration in ground-dwelling sciurids.

scholarly journals Mortality in relation to season, age, sex, and reproduction in Columbian ground squirrels (Spermophilus columbianus)

2001 ◽  
Vol 79 (3) ◽  
pp. 465-470 ◽  
Author(s):  
P Neuhaus ◽  
N Pelletier
Keyword(s):  
Ground Squirrels ◽  
Reproductive Status ◽  
Adult Males ◽  
Active Season ◽  
Life History Data ◽  
Spermophilus Columbianus ◽  
Trade Offs ◽  
Maternal Survival ◽  
Mortality Increase ◽  
Columbian Ground Squirrels

We investigated the timing of and age at mortality in Columbian ground squirrels (Spermophilus columbianus) in relation to sex and reproductive status. Life-history data were collected from 1994 to 1999 in the foothills of the Rocky Mountains, Alberta, Canada. We predicted increased mortality for males during mating and for females during lactation. Further, we expected reproductively successful females to have higher mortality than females that did not reproduce successfully. Finally we assumed that at some age reproductive success of females would decrease and mortality increase because of old age. For both sexes, survival over winter was high (ca. 90%) for adults. While there was a significant increase in mortality of adult males during the mating season, females did not have higher mortality during lactation than during the rest of the active season. Reproductive status influenced mortality in females: non-reproducing females had a higher chance of surviving than reproducing females. Females that weaned young were more likely to die after the weaning period than females that lost their litter during lactation. There was a positive correlation between maternal survival and survival of offspring to yearling age. Our results showed evidence of trade-offs between reproduction and survival of male and female Columbian ground squirrels.

Food and space: resources defended by territorial parous female Columbian ground squirrels

1994 ◽  
Vol 72 (11) ◽  
pp. 1908-1914 ◽  
Author(s):  
David A. Boag ◽  
Darwin R. Wiggett
Keyword(s):  
Body Mass ◽  
Significant Role ◽  
Ground Squirrel ◽  
Ground Squirrels ◽  
Differential Treatment ◽  
Adult Males ◽  
Spermophilus Columbianus ◽  
Columbian Ground Squirrels ◽  
Experimental Plots

The importance of food and space, as resources defended by parous female Columbian ground squirrels (Spermophilus columbianus), was studied by manipulating one of these resources, that is increasing the quality of forage (through urine fertilization) on small plots within territories. Use of these fertilized plots by ground squirrels increased more than 100-fold when averaged over 2 years after manipulation. This increase, however, was not equal for each sex and age class: parous females used the fertilized plots relatively more, and nonparous females less, than either yearling or adult males. The number of parous females with territories overlapping the experimental plots also increased after fertilization, but the size of their territories declined only slightly, by less than 10%. Parous females with access to the fertilized plots, relative to those without such access, had greater body mass and larger litters that both weighed more at birth and gained body mass subsequently more rapidly. Parous females on territories with fertilized plots showed higher levels of agonism than those on territories lacking such plots. Most of the agonism was centered on the experimental plots and more of it was directed at young of other females than at their own young. Such differential treatment of kin, however, did not extend to their offspring of the previous year. We suggest that for parous females of this ground squirrel, both food and space (at least that normally needed to supply sufficient forage) are important resources to defend, and both may have played a significant role in the evolution of territoriality in females of this species.

Seasonal activity and body mass of Columbian ground squirrels

1992 ◽  
Vol 70 (7) ◽  
pp. 1364-1368 ◽  
Author(s):  
F. Stephen Dobson ◽  
Michael J. Badry ◽  
Christine Geddes
Keyword(s):  
Body Mass ◽  
Growing Season ◽  
High Elevation ◽  
Ground Squirrels ◽  
Adult Males ◽  
Active Season ◽  
Spermophilus Columbianus ◽  
High Elevations ◽  
Columbian Ground Squirrels ◽  
Plant Growing Season

Recent research on Columbian ground squirrels (Spermophilus columbianus) has invoked the lengths of the active season and plant growing season to explain differences in life history and social behaviours among populations at different elevations. We evaluated an assumption of these studies that the active season for individual ground squirrels is significantly shorter at high than at low elevation. Adult males and females were active for about 100 days at low elevation and about 86 days at high elevation. Juvenile ground squirrels also had a longer active season at low (50 days) than at high elevation (45 days), but for yearlings the active season was similar (about 87 days). The active season for adults was about 2 weeks shorter than the plant growing season at low elevation, but up to 2 weeks longer than the plant growing season at high elevation. Differences in body mass of adult ground squirrels between low and high elevations at spring emergence from hibernation and at fall immergence into hibernation were consistent with a shorter active season and lower annual energy intake at high elevation, where adults were generally lighter. Examination of rates of weight gain during the active season showed that differences in adult weight could be explained by the length of the active season, but that yearlings and juveniles grew more rapidly at low than at high elevation. These results support the assumption that the active season for individual ground squirrels is generally shorter at high than at low elevation.

The resident fitness hypothesis and dispersal by yearling female Columbian ground squirrels

1992 ◽  
Vol 70 (10) ◽  
pp. 1984-1994 ◽  
Author(s):  
Darwin Wiggett ◽  
David A. Boag
Keyword(s):  
Resource Availability ◽  
Ground Squirrels ◽  
Home Ranges ◽  
Adult Males ◽  
Data Set ◽  
Individual Basis ◽  
Spermophilus Columbianus ◽  
Adult Females ◽  
Fitness Benefits ◽  
Columbian Ground Squirrels

The emigratory behavior of yearling female Columbian ground squirrels (Spermophilus columbianus) in southwestern Alberta was studied for 25 active seasons among five colonies. From this data set we tested six predictions of the resident fitness hypothesis. The data strongly supported all six predictions: (1) yearling females were highly philopatric; (2) mothers behaved cohesively towards their yearling daughters (adult females tended to shift their home ranges in the presence of yearling daughter(s), often facilitating the recruitment of the latter to the natal site); (3) as densities of adult resident females rose and resource availability on an individual basis presumably declined, agonism from parous mothers and neighboring females caused greater proportions of yearling females to emigrate; (4) sibling daughters competed for access to the natal site when this space became vacant (parous yearlings were more successful than their nonparous siblings, and among the latter, dominant individuals were more successful than their subordinate siblings); (5) resident adult females were highly aggressive towards immigrant yearling females; and (6) resident adult males behaved cohesively with all yearling females, whether resident or immigrant, and were significantly more cohesive towards yearling females than towards yearling males. The results of this study suggest that emigration is not adaptive for yearling female Columbian ground squirrels. Rather, we suggest that female Columbian ground squirrels gain fitness benefits through philopatry and the retention of daughter(s) on the natal site when resources are not limiting.

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.

Weight in relation to sex, age, and season in Columbian ground squirrels (Sciuridae: Rodentia)

1981 ◽  
Vol 59 (6) ◽  
pp. 999-1004 ◽  
Author(s):  
D. A. Boag ◽  
J. O. Murie
Keyword(s):  
Weight Gain ◽  
Ground Squirrels ◽  
Full Potential ◽  
Age Classes ◽  
Adult Weight ◽  
Spermophilus Columbianus ◽  
Large Colony ◽  
Potential Weight ◽  
Columbian Ground Squirrels

Annual weight gain in Columbian ground squirrels (Spermophilus columbianus) was studied over a period of 7 years in a large colony in southwestern Alberta. Juveniles approximately tripled their weight during the period from emergence to immergence, achieving about 60% of adult weight at onset of their first hibernation. Males were heavier than females and the weight gain in both sexes varied significantly among years. The weight characteristics of the age-classes up to 3 years were different from one another. Full potential weight was not achieved until squirrels were in their fourth summer. Males were always significantly heavier than females in nonjuvenile squirrels and the amount of weight gained by these classes varied significantly among years.

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