Natal dispersal in Columbian ground squirrels: is body mass the proximate stimulus?

1992 ◽  
Vol 70 (4) ◽  
pp. 649-653 ◽  
Author(s):  
Darwin R. Wiggett ◽  
David A. Boag
Keyword(s):  
Body Mass ◽  
Ground Squirrels ◽  
Natal Dispersal ◽  
Small Animals ◽  
Apparent Lack ◽  
Set Point ◽  
Spermophilus Columbianus ◽  
Wide Range ◽  
History Of ◽  
Columbian Ground Squirrels

Data on body mass and dispersal history of Columbian ground squirrels (Spermophilus columbianus) were collected at five colonies in southwestern Alberta. Two colonies were studied from 1983 to 1990 and three from 1984 to 1986. Body mass of yearling male dispersers did not differ significantly from that of nondispersers. Among dispersers, heavier animals did not disperse before lighter ones. Extremely small animals, however, may delay dispersal until they are 2 years old. Timing of dispersal was not apparently related to body mass; dispersing squirrels showed a wide range in body mass, with dispersal occurring synchronously at all colonies in all years despite significant differences in body mass of yearlings between colonies. The apparent lack of evidence for a critical body mass threshold for dispersal led us to conclude that the timing of dispersal in yearling male Columbian ground squirrels is not controlled at the proximate level by achieving a set point in body mass.

Intercolony natal dispersal in the Columbian ground squirrel

1989 ◽  
Vol 67 (1) ◽  
pp. 42-50 ◽  
Author(s):  
Darwin R. Wiggett ◽  
David A. Boag
Keyword(s):  
Ground Squirrel ◽  
Survival Rates ◽  
Ground Squirrels ◽  
Natal Dispersal ◽  
Male And Female ◽  
Spermophilus Columbianus ◽  
Median Distance ◽  
In Transit ◽  
Columbian Ground Squirrels ◽  
Actual Survival

Dispersal of Columbian ground squirrels (Spermophilus columbianus) among 16 colonies located in the Sheep River – Gorge Creek drainage of southwestern Alberta was studied from 1973 to 1986. In total, 73 intercolony movements involving 66 different animals were recorded. Intercolony dispersal movements were strongly biased towards males and were almost exclusively undertaken by 1-year-old squirrels (yearlings). The timing of emigration from the colonies studied was highly synchronous and was correlated with the dates of emergence of new litters. Yearling females that dispersed tended to leave at a later date than did yearling males. Most (91%) animals that dispersed moved to colonies <4 km away but movements of up to 8.5 km were recorded. There was no difference in median distance dispersed for male and female yearlings (2.0 and 1.8 km, respectively). Dispersing squirrels departed from colonies in nonrandom directions apparently following such features as trails and drainage systems. Such movement seemed to enhance the squirrels' chances of successfully locating nearby colonies. Minimum known survival rates while in transit for yearlings were 16% for males and 11% for females. Estimates of actual survival in transit for yearlings were 26% for males and 30% for females.

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 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.

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.

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