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.

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.

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.

Effects of reproduction on activity and foraging behaviour of adult female Columbian ground squirrels

1991 ◽  
Vol 69 (8) ◽  
pp. 2209-2216 ◽  
Author(s):  
R. Bruce MacWhirter
Keyword(s):  
Adult Female ◽  
Foraging Behaviour ◽  
Ground Squirrels ◽  
Absolute Amount ◽  
Short Term ◽  
Trade Off ◽  
Active Season ◽  
Spermophilus Columbianus ◽  
Time Of Breeding ◽  
Columbian Ground Squirrels

In this study I evaluated six ways in which adult female Columbian ground squirrels (Spermophilus columbianus) potentially alter their overall activity and foraging behaviour to satisfy the increased energetic needs of reproduction, all of which may involve a trade-off with predation risk. A sample of nonparous females was obtained by administering a short-term chemosterilant at the time of breeding. Relative to nonparous females, parous females spent more time above ground, more time foraging, and less time vigilant, particularly during lactation, and had a longer active season. Thus, in absolute terms, parous females spent more time exposed to aboveground predators than did nonparous females. Parous females spent less time at burrow entrances and, during lactation, were active farther from escape burrows than were nonparous females. Parous and nonparous females did not differ in the percentage of time spent vigilant during foraging bouts. These results indicate that females respond to the energetic demands of reproduction by increasing the absolute amount of time spent foraging, which entails an acceptance of an increase in exposure to predators, and not by modifying their behaviour during foraging bouts.

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.

Behavior and dispersal of yearling Columbian ground squirrels

1984 ◽  
Vol 62 (2) ◽  
pp. 161-167 ◽  
Author(s):  
Marco Festa-Bianchet ◽  
Wendy J. King
Keyword(s):  
Ground Squirrels ◽  
Dispersion Pattern ◽  
Dominance Status ◽  
Similar Frequency ◽  
Active Season ◽  
Spermophilus Columbianus ◽  
Play Behaviors ◽  
Intensive Observations ◽  
Columbian Ground Squirrels ◽  
Density Population

Behavior of yearling Columbian ground squirrels (Spermophilus columbianus) was studied through intensive observations of an isolated, high-density population in southwestern Alberta from 1979 to 1981. All members of this population were individually marked. A greater proportion of yearlings disappeared during the active season than that of any other age-class. This loss appeared to be due to emigration, and was greater for males than for females. Some 2-year-old males may also have dispersed. Male yearlings played more than females, but both sexes displayed a similar frequency of aggressive interactions with other yearlings. As the season progressed, the frequency of play behaviors between yearlings decreased, and by the time of presumed emigration almost no play was seen. There was no clear relationship between a yearling's dominance status and whether it emigrated. Adults of both sexes behaved aggressively towards yearlings, particularly yearling males. Adult females were most aggressive just preceding the time of presumed emigration, and at this time yearlings changed their dispersion pattern within the meadow, apparently in an attempt to avoid female aggression. Postponement of dispersal to the yearling age appears to be an adaptation to a short active season. Adult squirrels may benefit from expelling yearlings by diminishing future competition, but the adaptive advantage of emigration for the yearlings themselves remains unclear.

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.

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.

Effect of brief exposure to a potential predator on cortisol concentrations in female Columbian ground squirrels (Spermophilus columbianus)

2000 ◽  
Vol 78 (4) ◽  
pp. 578-587 ◽  
Author(s):  
Anne H Hubbs ◽  
John S Millar ◽  
John P Wiebe
Keyword(s):  
Blood Sample ◽  
Canis Familiaris ◽  
Ground Squirrels ◽  
Cortisol Response ◽  
Potential Predator ◽  
Active Season ◽  
Spermophilus Columbianus ◽  
Free Cortisol ◽  
Cortisol Levels ◽  
Columbian Ground Squirrels

We examined the effect of exposure to a potential predator on cortisol concentrations in captive female Columbian ground squirrels (Spermophilus columbianus) and determined if lactation mitigated this cortisol response. Lactating and nonlactating females were exposed to a dog (Canis familiaris) for 5 min once a week over a 8-week period. Blood was collected 5 min and 2.5 and 4.5 h after exposure to the dog. Females exposed to the dog had higher concentrations of total (but not free) cortisol than unexposed females only in the 5-min blood sample. Over the active season, total- and free-cortisol levels were 37-47% higher in females exposed to the dog than in unexposed females in early to mid-July when young were being weaned. The cortisol response to the dog was suppressed during lactation. Cortisol levels were, on average, 41-59% lower during lactation than during nonlactation 5 min (but not 2.5 or 4.5 h) after exposure to the dog.

Annual reproductive success in three cohorts of Columbian ground squirrels: founding immigrants, subsequent immigrants, and natal residents

1993 ◽  
Vol 71 (8) ◽  
pp. 1577-1584 ◽  
Author(s):  
Darwin R. Wiggett ◽  
David A. Boag
Keyword(s):  
Reproductive Success ◽  
Survival Rates ◽  
Ground Squirrels ◽  
Central Position ◽  
Adult Males ◽  
Male And Female ◽  
Reproductive Maturity ◽  
Active Season ◽  
Risk Of Predation ◽  
Columbian Ground Squirrels

We compared, over an 8-year period, the annual reproductive success (RS) of male and female founding immigrants (FIs) with that of subsequent immigrants (SIs), and the latter with that of natal residents (NRs) in two recently established colonies of Columbian ground squirrels (Spermophilus columbianus) in southwestern Alberta. For males, actual annual RS was unknown and so was estimated; for females, RS was measured directly. Among females, FIs had significantly more juveniles at litter emergence, and more yearlings present to age of emigration annually than did SIs. Juvenile and yearling offspring of SI females suffered higher annual rates of disappearance (presumed mortality) over the active season than did those of FIs. Additionally, the matrilines of FIs produced significantly more juveniles, more yearlings to time of emigration, and more daughters to reproductive maturity annually than did the matrilines of SI females. Male FIs had higher annual survival rates (and consequently lived and were territorial significantly longer), and had more female neighbours per year than did SIs, which suggests that the former had higher annual RS. We suggest that the higher annual RS of male and female FIs resulted mainly from their monopolization of the best resources and a lower risk of predation as a result of their more central position in the colony. Comparison of the annual RS of SIs and NRs showed that most (~70%) adult males present in the colonies were SIs. These males were significantly more likely to hold territories and to do so for significantly longer periods than their NR counterparts. Conversely, SI females annually brought above ground significantly fewer juveniles and had significantly fewer yearling offspring present to time of emigration than did NR females. Furthermore, the young of SI females suffered significantly higher rates of disappearance (presumed mortality) during the active season than did those of NR females, possibly because the former resided in more peripheral areas within the colony where predation rates may have been higher. We found no differences between these groups of females in the number of female offspring reaching reproductive maturity in the natal colony. These results provide preliminary support for the hypothesis that females, apart from FIs, benefit from philopatry; whereas males gain reproductive advantage through dispersal.

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