Evidence for source - sink dynamics in a regional population of arctic ground squirrels (Urocitellus parryii plesius)

Donker, Scott A.

doi:10.1071/wr11167

Cited by 20 publications

(14 citation statements)

References 42 publications

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“…Other studies provide evidence that biotic factors alone can form lower limits. For example, shrub habitats were considered population sinks for Arctic ground squirrels Urocitellus parryii due to high predation rates (Donker & Krebs, ). This dynamic was also confirmed for arctic hares Lepus arcticus through a series of experiments (Barta et al, ; Small & Keith, ).…”

Section: Review Of Evidence For Irltmentioning

confidence: 99%

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

Sirén

Morelli

2019

Journal of Animal Ecology

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A central theme of range‐limit theory (RLT) posits that abiotic factors form high‐latitude/altitude limits, whereas biotic interactions create lower limits. This hypothesis, often credited to Charles Darwin, is a pattern widely assumed to occur in nature. However, abiotic factors can impose constraints on both limits and there is scant evidence to support the latter prediction. Deviations from these predictions may arise from correlations between abiotic factors and biotic interactions, as a lack of data to evaluate the hypothesis, or be an artifact of scale. Combining two tenets of ecology—niche theory and predator–prey theory—provides an opportunity to understand how biotic interactions influence range limits and how this varies by trophic level. We propose an expansion of RLT, interactive RLT (iRLT), to understand the causes of range limits and predict range shifts. Incorporating the main predictions of Darwin's hypothesis, iRLT hypothesizes that abiotic and biotic factors can interact to impact both limits of a species’ range. We summarize current thinking on range limits and perform an integrative review to evaluate support for iRLT and trophic differences along range margins, surveying the mammal community along the boreal‐temperate and forest‐tundra ecotones of North America. Our review suggests that range‐limit dynamics are more nuanced and interactive than classically predicted by RLT. Many (57 of 70) studies indicate that biotic factors can ameliorate harsh climatic conditions along high‐latitude/altitude limits. Conversely, abiotic factors can also mediate biotic interactions along low‐latitude/altitude limits (44 of 68 studies). Both scenarios facilitate range expansion, contraction or stability depending on the strength and the direction of the abiotic or biotic factors. As predicted, biotic interactions most often occurred along lower limits, yet there were trophic differences. Carnivores were only limited by competitive interactions (n = 25), whereas herbivores were more influenced by predation and parasitism (77%; 55 of 71 studies). We highlight how these differences may create divergent range patterns along lower limits. We conclude by (a) summarizing iRLT; (b) contrasting how our model system and others fit this hypothesis and (c) suggesting future directions for evaluating iRLT.

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Section: Review Of Evidence For Irltmentioning

confidence: 99%

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

Sirén

Morelli

2019

Journal of Animal Ecology

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“…For example, female Columbian ground squirrels (Spermophilus columbianus (Ord, 1815) = Urocitellus columbianus (Ord, 1815)) that are lighter during spring will often not reproduce, but experience greater subsequent overwinter survival compared with heavier females that successfully raise litters (Neuhaus 2000). Similarly, Donker and Krebs (2012) found that AGS overwinter survival was higher, but reproduction was lower, in the boreal forest habitat than in the low meadow habitat.…”

Section: Body Massmentioning

confidence: 89%

Forest or meadow: the consequences of habitat for the condition of female arctic ground squirrels (Urocitellus parryii plesius)

2015

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Body condition of animals influences the likelihood of surviving harsh environmental conditions, successfully reproducing, and resisting disease. The sum of these individual components of fitness, in turn, have consequences for the growth and persistence of wildlife populations. Here we compared the body mass and condition of adult female arctic ground squirrels (Urocitellus parryii plesius (Osgood, 1900)), an obligate hibernator, in source and sink habitats. We tested the hypothesis that adult females would be in poorer condition in the boreal forest than in adjacent meadows. We found that, during spring, postpartum females in forests weighed less (405 ± 7 vs. 437 ± 11 g; mean ± SE) and were in poorer condition (mean (±SE) residual of mass over structural size = −11.0 ± 10.2 vs. 20.5 ± 6.1 g) compared with females in meadow-source habitat. However, by the onset of entrance into hibernation in August, forest squirrels had reached parity with meadow squirrels and no difference was found in mass (519 ± 13 vs. 520 ± 15 g; mean ± SE) or condition (residual index = −0.01 ± 0.01 vs. 0.03 ± 0.01; mean ± SE). We suggest that for squirrels in formerly occupied boreal forests, (i) poor spring body condition decreased reproductive success and (ii) achieving compensatory growth, via increased foraging, comes at the costs of higher predation risk. These costs likely contributed to the recent local extinction of arctic ground squirrels in boreal forest habitat.Résumé : L'embonpoint des animaux influence la probabilité de survie dans des conditions ambiantes difficiles, le succès de reproduction et la résistance aux maladies. La somme de ces différentes composantes de l'aptitude a, quant à elle, des conséquences en ce qui concerne la croissance et la persistance des populations d'animaux sauvages. Nous comparons la masse corporelle et l'embonpoint de spermophiles arctiques (Urocitellus parryii plesius (Osgood, 1900)) femelles adultes, une espèce hibernante inféodée, dans des habitats sources et puits. Nous vérifions l'hypothèse selon laquelle les femelles adultes présenteraient un moins bon embonpoint dans la forêt boréale que dans les baissières adjacentes. Nous avons constaté que, au printemps, les femelles post-partum dans les forêts présentaient une masse (405 ± 7 contre 437 ± 11 g; moyenne ± ET) et un embonpoint (résidue moyenne (±ET) de la masse sur la taille structurale = −11,0 ± 10,2 contre 20,5 ± 6,1 g) inférieurs à ceux des femelles dans les habitats sources de baissière. Cependant, au début de l'entrée en hibernation en août, les spermophiles des forêts avaient atteint la parité avec les spermophiles des baissières et aucune différence de masse (519 ± 13 contre 520 ± 15 g; moyenne ± ET), ni d'embonpoint n'était observée (indice résiduel = −0,01 ± 0,01 contre 0,03 ± 0,01; moyenne ± ET). Nous proposons que, pour les spermophiles dans des forêts boréales occupées antérieurement, (i) le faible embonpoint printanier réduisait le succès de reproduction et (ii) la compensation de la croissance par un approvisionnement accru...

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“…Such systems, defined as 'duck holes', may represent more transient colonies in marginal habitat or burrowing activity associated with territorial disputes or interactions with predators (Carl 1971). The potential for source-sink dynamics has been suggested for arctic ground squirrels (Gillis et al 2005a;Donker and Krebs 2012). Burrowing activity with such characteristics may be indicative of sink-like populations or transient habitat associations.…”

Section: Discussionmentioning

confidence: 99%

“…Indications of source-sink dynamics have been identified in arctic ground squirrels (Donker and Krebs 2012) and allow this species to occur in marginal habitat. Habitats of marginal quality may become less frequently occupied if high-quality (presumably forb-rich and lacking in dense high-stature vegetation) habitat becomes rarer.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2015

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Increases in terrestrial primary productivity across the Arctic and northern alpine ecosystems are leading to altered vegetation composition and stature. Changes in vegetation stature may affect predator-prey interactions via changes in the prey's ability to detect predators, changes in predation pressure, predator identity and predator foraging strategy. Changes in productivity and vegetation composition may also affect herbivores via effects on forage availability and quality. We investigated if height-dependent effects of forage and non-forage vegetation determine burrowing extent and activity of arctic ground squirrels (Urocitellus parryii). We collected data on burrow networks and activity of arctic ground squirrels across long-term vegetation monitoring sites in Denali National Park and Preserve, Alaska. The implications of height-specific cover of potential forage and non-forage vegetation on burrowing behaviour and habitat suitability for arctic ground squirrels were investigated using hierarchical Bayesian modelling. Increased cover of forbs was associated with more burrows and burrow systems, and higher activity of systems, for all forb heights. No other potential forage functional group was related to burrow distribution and activity. In contrast, height-dependent negative effects of non-forage vegetation were observed, with cover over 50-cm height negatively affecting the number of burrows, systems and system activity. Our results demonstrate that increases in vegetation productivity have dual, potentially counteracting effects on arctic ground squirrels via changes in forage and vegetation stature. Importantly, increases in tall-growing woody vegetation (shrubs and trees) have clear negative effects, whereas increases in forb should benefit arctic ground squirrels.

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Evidence for source - sink dynamics in a regional population of arctic ground squirrels (Urocitellus parryii plesius)

Cited by 20 publications

References 42 publications

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

Forest or meadow: the consequences of habitat for the condition of female arctic ground squirrels (Urocitellus parryii plesius)

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

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