Annual Variation of Spring Emergence and Breeding in Columbian Ground Squirrels (Spermophilus columbianus)

Murie, Jan O.; Harris, Margaret

doi:10.2307/1380440

Cited by 144 publications

(145 citation statements)

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“…Ground squirrels were active only for about 4 months each year, hibernating during the remaining 8 months (Dobson et al 1992;Murie and Harris 1982). Females usually bred within the 1st week after emergence, giving birth 24 days later (Murie and Boag 1984;Murie and Harris 1982).…”

Section: Methodsmentioning

confidence: 99%

“…To get exact mating dates, females were examined for their sexual condition (degree of swelling of the vulva-Murie and Harris 1982). When no direct observations were available, I backdated mating dates by subtracting 51 days from juvenile emergence (Murie and Harris 1982). I classified females that weaned Ն1 juvenile as successfully reproducing females; females that did not wean juveniles were unsuccessful.…”

Section: Methodsmentioning

confidence: 99%

“…I must have missed their emergence from or immergence into hibernation because it was unlikely to have occurred at those times (Dobson et al 1992;Murie and Harris 1982;Young 1990). To calculate daily and total weight loss during hibernation, only animals caught Ͻ1 day of the observed emergence and immergence date were used.…”

Section: Methodsmentioning

confidence: 99%

“…Because reproduction is energetically costly, parents should try to optimize timing of reproduction to minimize net energy expenditure and maximize investment in offspring. In many birds (Gauthier 1989;Morton and Derrickson 1990;Olsson 1996;Schoech 1996;Verhulst and Tinbergen 1991), black-tailed prairie dogs (Cynomys ludovicianus -Hoogland 1995), Unita ground squirrels (S. armatus -Rieger 1996), and Columbian ground squirrels (S. columbianus- Murie and Harris 1982), ear-* Correspondent: peter neuhaus@hotmail.com ly mating results in higher reproductive success. Many factors affect timing of mating, such as food availability (Ben-David 1997;Benkman 1990;Churchill 1994;Komdeur 1996;Schoech 1996;Young 1996), parasite abundance (Oppliger et al 1994), weather conditions, (Grindall et al 1992;Murie and Harris 1982), parental body condition (Mitchell and Lincoln 1973;Newton and Marquiss 1984), quality of habitat, and parental experience (Gauthier 1989;Morton and Derrickson 1990).…”

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confidence: 99%

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Timing of Hibernation and Molt in Female Columbian Ground Squirrels

Neuhaus¹

2000

Journal of Mammalogy

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Timing of activity, seasonal changes in food availability, environmental fluctuations, and costs of reproduction are important determinants of an animal's life history. In mountain ground squirrels (Spermophilus), the shortness of the active season influences how they time their activities. I studied timing of the active season, reproduction, and weight loss during hibernation in Columbian ground squirrels (S. columbianus) in Alberta, Canada, from the summer of 1994 to the spring of 1998. Entry into hibernation and emergence from hibernation the following year were earlier for females that did not wean a litter compared with those that did. The active season was shorter and hibernation longer for unsuccessful females than for successful females. Molt of females was earlier when they did not wean a litter than when they did. Date of mating had no influence on success in weaning a litter, but juveniles surviving to yearling age came from litters born earlier than juveniles that did not survive to yearling age. In successfully reproducing females, early entry into hibernation was associated with early mating. Daily and total weight loss during hibernation was higher in females that weaned young than in females that did not wean young.Key words: body mass, ground squirrel, hibernation, molt, reproduction, Spermophilus columbianus Herbivores in temperate zones are faced with a short growing season of plants. Often only 1 season of the year is ideal for raising young, and thus timing of breeding is important for maximizing reproductive success. Because reproduction is energetically costly, parents should try to optimize timing of reproduction to minimize net energy expenditure and maximize investment in offspring. In many birds (Gauthier 1989;Morton and Derrickson 1990;Olsson 1996;Schoech 1996;Verhulst and Tinbergen 1991), black-tailed prairie dogs (Cynomys ludovicianus-Hoogland 1995), Unita ground squirrels (S. armatus-Rieger 1996), and Columbian ground squirrels (S. columbianus-Murie and Harris 1982), ear-* Correspondent: peter neuhaus@hotmail.com ly mating results in higher reproductive success. Many factors affect timing of mating, such as food availability

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Timing of Hibernation and Molt in Female Columbian Ground Squirrels

Neuhaus¹

2000

Journal of Mammalogy

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“…We assessed squirrels for reproductive status and assumed breeding date based on observation of genitalia as described by Murie and Harris (1982). We estimated parturition based on a 28 d gestation period (Choromanski-Norris et al 1986) and observed weight loss > 40 g over a 24 hr period.…”

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confidence: 99%

Costs of Franklin’s ground squirrel (Poliocitellusfranklinii) ectoparasitism reveal adaptive sex allocation

Pero

Hare

2018

Can. J. Zool.

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sham-treated dams in body mass, litter size, or juvenile mass, and thus, dam growth and reproduction were not compromised by ectoparasite defense at the infestation levels experienced in this study. Litter sex ratio differed significantly between insecticide-treated and control females, however, with a higher proportion of male offspring produced among females with reduced ectoparasite load. Our findings are thus consistent with the Trivers-Willard model for adaptive sex allocation, yet provide novel comparative insight into how sociality may modulate the expression of adaptive sex allocation among small mammals given the differential payoff associated with the production of high-quality female versus male offspring in more social versus less social species.

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Testing the reproductive and somatic trade‐off in female Columbian ground squirrels

Rubach

Abebe

et al. 2016

Ecology and Evolution

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Energetic trade‐offs in resource allocation form the basis of life‐history theory, which predicts that reproductive allocation in a given season should negatively affect future reproduction or individual survival. We examined how allocation of resources differed between successful and unsuccessful breeding female Columbian ground squirrels to discern any effects of resource allocation on reproductive and somatic efforts. We compared the survival rates, subsequent reprodction, and mass gain of successful breeders (females that successfully weaned young) and unsuccessful breeders (females that failed to give birth or wean young) and investigated “carryover” effects to the next year. Starting capital was an important factor influencing whether successful reproduction was initiated or not, as females with the lowest spring emergence masses did not give birth to a litter in that year. Females that were successful and unsuccessful at breeding in one year, however, were equally likely to be successful breeders in the next year and at very similar litter sizes. Although successful and unsuccessful breeding females showed no difference in over winter survival, females that failed to wean a litter gained additional mass during the season when they failed. The next year, those females had increased energy “capital” in the spring, leading to larger litter sizes. Columbian ground squirrels appear to act as income breeders that also rely on stored capital to increase their propensity for future reproduction. Failed breeders in one year “prepare” for future reproduction by accumulating additional mass, which is “carried over” to the subsequent reproductive season.

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Annual Variation of Spring Emergence and Breeding in Columbian Ground Squirrels (Spermophilus columbianus)

Cited by 144 publications

References 20 publications

Timing of Hibernation and Molt in Female Columbian Ground Squirrels

Timing of Hibernation and Molt in Female Columbian Ground Squirrels

Costs of Franklin’s ground squirrel (Poliocitellusfranklinii) ectoparasitism reveal adaptive sex allocation

Testing the reproductive and somatic trade‐off in female Columbian ground squirrels

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