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

Abstract

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...

How will the greening of the Arctic affect an important prey species and disturbance agent? Vegetation effects on arctic ground squirrels

“…Another possibility is that steeper slopes are associated with better visibility and Our results indicate that forbs are likely to be important forage for arctic ground squirrels. This is supported by prior evidence from analysis of stomach contents, seasonal diet and cheek pouch contents (Batzli and Sobaski 1980;McLean 1985;Gillis et al 2005b). There was no evidence that other functional groups were routinely important to the same extent, although single species within other functional groups may be individually influential.…”

“…Arctic ground squirrels occur in alpine and arctic tundra, shrub-tundra, shrub, boreal forest and meadow habitats; reported densities vary from 0.1 to 16 squirrels per hectare (Wheeler and Hik 2013). Although broadly generalist in their diet, evidence from caching behaviour and stomach contents suggests there is a degree of selectivity in foraging, with particular avoidance of evergreen shrub and lichen (Batzli and Sobaski 1980;Gillis et al 2005b). Diet at one site varied seasonally, with a preference for forbs in the middle of the active season and more varied diet at the start and end.…”

Circannual Transitions in Gene Expression

“…Generally, hibernating mammals do not use food consumption as a source of energy, although there are some instances of food caching (Gillis et al, 2005). Some ground squirrel species will not eat any food during hibernation, even if it is offered artificially in the lab (Torke and Twente, 1977).…”

Hibernation and Circadian Rhythms of Body Temperature in Free-Living Arctic Ground Squirrels

“…Animals spend the remainder of the year sequestered in frozen burrow systems (hibernacula) alternating between long (2-3 wk) bouts of continuous torpor ( C; Barnes T ≥ Ϫ2.9Њ b 1989) interrupted by brief (10-20 h) intervals of euthermic T b (35Њ-37ЊC) during interbout arousal episodes (Buck et al 2008). While males terminate heterothermy and feed from cached food for 2-3 wk before first emerging to the surface (Barnes 1996), females are not thought to cache food (Gillis et al 2005) and typically emerge from their burrows and resume daily activity within 4 d of terminating heterothermy (Sheriff et al 2011).…”