Sexual Differences in Reproductive Effort of Richardson's Ground Squirrels

Michener, Gail R.

doi:10.2307/1382838

Cited by 72 publications

(64 citation statements)

References 39 publications

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“…In Richardson's ground squirrels, males gain access to estrous females by chasing and fighting with other males, leading to mass loss during the mating season, which explains the high male mortality during this period (Michener 1984(Michener , 1998Michener and McLean 1996). A similar pattern is evident in Columbian ground squirrels, where males do not gain mass during the mating season whereas females do gain mass (Murie and Harris 1978;Boag and Murie 1981).…”

Section: Introductionmentioning

confidence: 83%

“…These differences are not only due to the male-biased dispersal (Boag and Murie 1981;Festa-Bianchet and King 1984) but might also reflect high reproductive costs during the mating season (Neuhaus et al 1999). In Richardson's ground squirrels (Spermophilus richardsonii), adult mortality was higher in males than in females during the mating season, active season, and the whole year (Michener and Locklear 1990;Michener 1998). Trade-offs between predation risk and foraging have been shown to exist in Belding's ground squirrels (Spermophilus beldingi), where well-fed animals showed more vigilance than deprived individuals (Bachman 1993).…”

Section: Introductionmentioning

confidence: 99%

“…Females on the other hand invest most energy directly into their offspring during gestation and lactation (Michener 1998). In various mammals, lactation is the most costly part of female reproduction (König et al 1988;Clutton-Brock et al 1989;Atramenotowicz 1992).…”

Section: Introductionmentioning

confidence: 99%

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

Neuhaus¹,

Pelletier²

2001

Can. J. Zool.

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Abstract: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.Résumé : Nous avons étudié la phénologie de la mortalité et déterminé l'âge au décès chez le Spermophile du Columbia (Spermophilus columbianus) en fonction du sexe et du statut reproducteur à partir de données démograph-iques recueillies de 1994 à 1999 sur les contreforts des Rocheuses en Alberta, Canada. Nous avons posé en hypothèse que la mortalité augmenterait chez les mâles au cours de la période des accouplements et chez les femelles durant l'allaitement et que les femelles qui réussiraient leur reproduction auraient une mortalité plus forte que les femelles qui la rateraient. Enfin, nous nous attendions à un déclin de la reproduction chez les femelles à partir d'un certain âge et à une augmentation de la mortalité due à la vieillesse. Chez les adultes mâles et femelles, la survie en hiver est élevée (ca. 90 %). Il se produit une augmentation significative de la mortalité des mâles pendant la saison des accouplements, mais les femelles n'ont pas un taux de mortalité plus élevé durant l'allaitement que pendant le reste de la saison d'activité. Le statut reproducteur influence la mortalité chez les femelles : en effet, les femelles non reproductrices ont de meilleures chances de survie que les femelles reproductrices. La probabilité de mourir est plus forte chez les femelles qui gardent leurs petits jusqu'au sevrage que chez celles qui perdent leur portée pendant l'allaitement. Il y a une corrélation positive entre la survie des femelles et la survie des jeunes au cours de la première année. Nos résultats indiquent qu'il s'établit des compromis entre la reproduction et la survie chez les mâles et les femelles du Spermophile du Columbia.[Traduit par la Rédaction] 470Neuha...

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Section: Introductionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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

Neuhaus¹,

Pelletier²

2001

Can. J. Zool.

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“…1 and 2). These differences are likely the result of different motivations for carrying material-either for immediate use or for caching (Michener, 1993). Compared with males, females carried material less frequently and did so earlier in the season (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, females, who do not cache seeds, emerge from hibernation three to six days after becoming euthermic weighing 30% less than they did the previous fall (Buck and Ritter, 1993;Buck and Barnes, 1999). The sex difference in caching behaviour is related to the higher cost of breeding for males (Michener, 1998;Buck and Barnes, 1999). Not only must males increase body temperature before the breeding season to facilitate sperm production, but they engage in intense male-male competition for mating opportunities when vegetation is still snow-covered and unavailable (Carl, 1971).…”

Section: Introductionmentioning

confidence: 99%

Evidence for Selective Caching by Arctic Ground Squirrels Living in Alpine Meadows in the Yukon

Gillis¹,

Morrison²,

Zazula³

et al. 2010

ARCTIC

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ABSTRACT. Male arctic ground squirrels (Spermophilus parryii) rely on food they cached the previous year for the energy they need to compete for mates each spring. We collected cheek-pouch contents of arctic ground squirrels trapped during three summers as an indication of what squirrels cached. Among adults, both males and females carried material in their cheek pouches, but males did so more frequently than females (4.4% vs. 0.6% of captures). Males carried material later in the summer than females, and also carried different material (seeds and rhizomes as opposed to nesting material). These differences probably reflect different purposes of cheek-pouch contents-females carried material for immediate use, whereas males carried food for caching. Only 24 of over 100 species of vascular plants growing at our alpine study site were carried, and presumably cached, by male arctic ground squirrels. The seeds or rhizomes of one species, Polygonum viviparum, were found in over 90% of cheek-pouch contents examined, even though that species grew at relatively low density and was no more common than another species in the same genus (Polygonum bistorta) that was never found in cheek-pouch contents. Collectively, this evidence indicates that males are highly selective in what species they cache. Many of the species carried by arctic ground squirrels in this study have also been found in Pleistocene fossil caches from central Yukon, indicating that food preferences of this species may have remained stable over time.Key words: arctic ground squirrel, Spermophilus parryii, food caching, hoarding, Polygonum, alpine RÉSUMÉ. Les spermophiles arctiques mâles (Spermophilus parryii) dépendent de la nourriture qu'ils ont cachée l'année précédente pour obtenir l'énergie dont ils ont besoin pour se trouver une compagne d'accouplement au printemps. On a recueilli le contenu des abajoues de spermophiles arctiques capturés pendant trois étés (de 2000 à 2002) pour obtenir un aperçu de ce qu'ils emmagasinaient. Les spermophiles adultes, tant mâles que femelles, transportaient des matériaux dans leurs abajoues, mais c'était plus souvent le cas chez les mâles que chez les femelles (4,4 % par rapport à 0,6 % des spermophiles capturés). Les mâles transportaient des matériaux plus tard pendant l'été que les femelles, sans compter que ces matériaux étaient différents (des graines et des rhizomes par opposition à des matériaux destinés à la nidification). Ces différences sont probablement le reflet de la raison d'être différente du contenu des abajoues -les femelles transportaient des matériaux dont elles allaient se servir immédiatement, tandis que les mâles transportaient des aliments qu'ils allaient mettre en réserve. Sur la centaine d'espèces de plantes vasculaires poussant au site alpin que nous avons étudié, seulement 24 d'entre elles étaient présentes. Ces plantes avaient probablement été mises en réserve par les spermophiles arctiques mâles. Les graines ou les rhizomes d'une espèce, soit le Polygonum viviparum, ont été trouvés dans plus...

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Central distribution of oxytocin and vasopressin 1a receptors in juvenile Richardson’s ground squirrels

Freeman

Hare

Caldwell

2019

J of Neuroscience Research

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Oxytocin and vasopressin are well‐conserved peptides important to the regulation of numerous aspects of social behavior, including sociality. Research exploring the distribution of the receptors for oxytocin (Oxtr) and for vasopressin (Avpr1a) in mammals has revealed associations between receptor distribution, sociality, and species’ mating systems. Given that sociality and gregariousness can be tightly linked to reproduction, these nonapeptides unsurprisingly support affiliative behaviors that are important for mating and offspring care. We localized these receptors in juvenile Richardson’s ground squirrel brains to determine whether distribution patterns of Oxtr and Avpr1a that are associated with promiscuous mating systems differ in rodents that also exhibit non‐reproductive affiliation. These squirrels are social, colonial, and engage in nepotistic alarm calling behavior and affiliation outside of a reproductive context. Juveniles are the most affiliative age‐class and are non‐reproductive; making them ideal for examining these associations. We found that juveniles had dense Oxtr binding in the dentate gyrus of the hippocampus, amygdala, lateral septum, bed nucleus of the stria terminalis and medial geniculate nucleus. Juveniles had low to modest levels of Avpr1a binding in the medial preoptic area, olfactory bulbs, nucleus accumbens, superior colliculus, and inferior colliculus. We noted Oxtr and Avpr1a binding in the social behavior neural network (SBNN), further supporting a role of these nonapeptides in modulating social behavior across taxa. Oxtr and Avpr1a binding was also present in brain regions important to auditory processing that have known projections to the SBNN. We speculate that these neural substrates may be where these nonapeptides regulate communication.

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Sexual Differences in Reproductive Effort of Richardson's Ground Squirrels

Cited by 72 publications

References 39 publications

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

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

Evidence for Selective Caching by Arctic Ground Squirrels Living in Alpine Meadows in the Yukon

Central distribution of oxytocin and vasopressin 1a receptors in juvenile Richardson’s ground squirrels

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