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.

Intraspecific killing of preweaned young in the Columbian ground squirrel, Spermophilus columbianus

1991 ◽  
Vol 69 (3) ◽  
pp. 797-800 ◽  
Author(s):  
James F. Hare
Keyword(s):  
Ground Squirrel ◽  
Ground Squirrels ◽  
Equal Access ◽  
Male And Female ◽  
Spermophilus Columbianus ◽  
Columbian Ground Squirrels

The abandonment of Columbian ground squirrel (Spermophilus columbianus) neonates by their dams when dams and litters were released from field enclosures resulted in the availability of newborn pups aboveground to male and female conspecifics. Four incidents of infanticide were observed and, without exception, perpetrators of infanticide were female, although male conspecifics had equal access to pups. Contrary to an earlier conjecture that male Columbian ground squirrels are the more likely perpetrators of infanticide, this finding is consistent with the majority of incidents documented for this species.

Spacing of female kin in Columbian ground squirrels (Spermophilus columbianus)

1989 ◽  
Vol 67 (1) ◽  
pp. 91-95 ◽  
Author(s):  
Wendy J. King
Keyword(s):  
Ground Squirrels ◽  
High Density ◽  
High Density Population ◽  
Spermophilus Columbianus ◽  
Close Relatives ◽  
Columbian Ground Squirrels ◽  
Density Population

The dispersion of matrilineally related females was examined within a high-density population of Columbian ground squirrels (Spermophilus columbianus) in southwestern Alberta. Females tended to nest near their natal site when no other female occupied it. Breeding females spaced themselves evenly so that close relatives formed intact groups but not dense clusters. The kin group was typically composed of a mother with one or two daughters that were nonlittermate sisters. Females appeared to be attracted to natal areas and the resources they contained, perhaps burrows.

Reproduction in yearling female Columbian ground squirrels (Spermophilus columbianus)

1981 ◽  
Vol 59 (6) ◽  
pp. 1032-1035 ◽  
Author(s):  
M. Festa-Bianchet
Keyword(s):  
Weight Gain ◽  
Sexual Development ◽  
Weather Conditions ◽  
Ground Squirrels ◽  
Lower Weight ◽  
Spermophilus Columbianus ◽  
Adult Females ◽  
Lower Weight Gain ◽  
Columbian Ground Squirrels ◽  
Similar Growth

In 1980, 4 of 13 yearling female Columbian ground squirrels in a colony in southwestern Alberta raised litters. Mean litter size was not significantly smaller than that of adult females. Breeding and nonbreeding yearling females had similar growth rates as juveniles in 1979, but the former had a lower weight gain in 1980 before their young were weaned. Breeding yearling females were more aggressive and played less than nonbreeders. A combination of apparently good habitat quality in the study area and favourable weather conditions during summer of 1979 and in May of 1980 may have produced early sexual development of these females.

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