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Olivier Gilg - One of the best experts on this subject based on the ideXlab platform.

  • Are gastrointestinal parasites associated with the cyclic population dynamics of their arctic Lemming hosts?
    International Journal for Parasitology: Parasites and Wildlife, 2019
    Co-Authors: Olivier Gilg, Benoît Sittler, Niels Martin Schmidt, Loïc Bollache, Eve Afonso, Glenn Yannic, Lars Holst Hansen, Jannik Hansen, Johannes Lang, Nicolas Meyer
    Abstract:

    Many rodents, including most populations of arctic Lemmings (genus Dicrostonyx and Lemmus), have cyclic population dynamics. Among the numerous hypotheses which have been proposed and tested to explain this typical characteristic of some terrestrial vertebrate communities, trophic interactions have often been presented as the most likely drivers of these periodic fluctuations. The possible role of parasites has, however, only seldom been assessed. In this study, we genetically measured the prevalence of two endoparasite taxa, eimerians and cestodes, in 372 faecal samples from collared Lemmings, over a five year period and across three distant sites in Northeast Greenland. Prevalence of cestodes was low (2.7% over all sites and years) and this taxon was only found at one site (although in 4 out of 5 years) in adult hosts. By contrast, we found high prevalence for eimerians (77.7% over all sites and years), which occurred at all sites, in every year, for both age classes (at the Hochstetter Forland site where both adult and juvenile faeces were collected) and regardless of reproductive and social status inferred from the characteristics of the Lemming nests where the samples had been collected. Prevalence of eimerians significantly varied among years (not among sites) and was higher for juvenile than for adult Lemmings at the Hochstetter Forland site. However, higher prevalence of eimerians (P t ) was only associated with lower Lemming density (N t ) at one of the three sites and we found no delayed density dependence between N t and P t+1 to support the parasite hypothesis. Our results show that there is no clear relation between Lemming density and eimerian faecal prevalence in Northeast Greenland and hence no evidence that eimerians could be driving the cyclic population dynamics of collared Lemmings in this region.

  • Demographic responses of a site-faithful and territorial predator to its fluctuating prey: long-tailed skuas and arctic Lemmings.
    Journal of Animal Ecology, 2014
    Co-Authors: Frederic Barraquand, Benoît Sittler, Olivier Gilg, John-andré Henden, Toke T. Høye, Nigel G. Yoccoz, Niels M. Schmidt, Rolf A. Ims
    Abstract:

    Environmental variability, through interannual variation in food availability or climatic variables, is usually detrimental to population growth. It can even select for constancy in key life-history traits, though some exceptions are known. Changes in the level of environmental variability are therefore important to predict population growth or life-history evolution. Recently, several cyclic vole and Lemming populations have shown large dynamical changes that might affect the demography or life-histories of rodent predators. Skuas constitute an important case study among rodent predators, because of their strongly saturating breeding productivity (they lay only two eggs) and high degree of site fidelity, in which they differ from nomadic predators raising large broods in good rodent years. This suggests that they cannot capitalize on Lemming peaks to the same extent as nomadic predators and might be more vulnerable to collapses of rodent cycles. We develop a model for the population dynamics of long-tailed skuas feeding on Lemmings to assess the demographic consequences of such variable and non-stationary prey dynamics, based on data collected in NE Greenland. The model shows that populations of long-tailed skua sustain well changes in Lemming dynamics, including temporary collapses (e.g. 10 years). A high floater-to-breeder ratio emerges from rigid territorial behaviour and a long-life expectancy, which buffers the impact of adult abundance's decrease on the population reproductive output. The size of the floater compartment is affected by changes in both mean and coefficient of variation of Lemming densities (but not cycle amplitude and periodicity per se). In Greenland, the average Lemming density is below the threshold density required for successful breeding (including during normally cyclic periods). Due to Jensen's inequality, skuas therefore benefit from Lemming variability; a positive effect of environmental variation. Long-tailed skua populations are strongly adapted to fluctuating Lemming populations, an instance of demographic lability in the reproduction rate. They are also little affected by poor Lemming periods, if there are enough floaters, or juveniles disperse to neighbouring populations. The status of Greenland skua populations therefore strongly depends upon floater numbers and juvenile movements, which are not known. This reveals a need to intensify colour-ringing efforts on the long-tailed skua at a circumpolar scale.

  • SUPPORTING ONLINE MATERIAL Cyclic dynamics in a simple vertebrate predator-prey community
    2014
    Co-Authors: Olivier Gilg, Ilkka Hanski, Benoît Sittler
    Abstract:

    In our model (main article), the numbers of Lemmings predated by the arctic fox, the long-tailed skua and the snowy owl were calculated based on the functional and numerical responses of the predators presented in Fig. 1 (main article). All these species feed mostly on Lemmings, which account for>90 % of their diet when Lemming densities are>1 ind./ha. At lower Lemming densities, the main alternate prey are birds (ptarmigan, waders and passerines) for the snowy owl, small birds, fishes, invertebrates and berries for the long-tailed skua, and arctic hare, muskox carrion, birds, eggs, invertebrates and berries for the arctic fox (O. Gilg et al. in prep.). Below, we present a more detailed description of the methods used to calculate (i) the functional and (ii) numerical responses of these predators to the Lemming density, (iii) the fieldestimated parameter values (Table S1), and (iv) how we implemented the numerical responses in the model (the functional responses were simply added to the prey equation as presented in the main article). Additionally, we describe (v) how we estimated the Lemming density at snowmelt (N’) based on the density of winter nests for 1988-2002 and on direct live-trapping for 1998-2002. We present (vi) the empirical support for lack of space or food limitation in Lemming dynamics. W

  • Functional and numerical responses of four Lemming predators in high arctic Greenland.
    Oikos, 2006
    Co-Authors: Olivier Gilg, Benoît Sittler, Brigitte Sabard, Arnaud Hurstel, Raphaël Sané, Pierre Delattre, Ilkka Hanski
    Abstract:

    The high-arctic tundra ecosystem has the world's simplest vertebrate predator-/prey community, with only four predators preying upon one rodent species, the collared Lemming (Dicrostonyx groenlandicus ). We document the functional and numerical responses of all the four predators in NE Greenland. Using these data, we assess the impact of predation on the dynamics of the collared Lemming with a 4 yr cycle and >100-fold difference between maximum and minimum densities. All predator species feed mostly (>90%) on Lemmings when Lemming density is >1 ha-1, but the shapes of the predators' responses vary greatly. The snowy owl (Nyctea scandiaca) is present and breeds only when Lemming densities at snowmelt are >2 ha-1, giving rise to a step-like numerical response. The long-tailed skua (Stercorarius longicaudus ) has a type III functional response and shifts from alternate food (mainly berries and insects) to Lemmings with increasing Lemming density. The skua surpasses all the other predators in summer by its total response. The type III functional response of the Arctic fox (Alopex lagopus ) starts to increase at much lower Lemming densities than the responses of the avian predators, but it has only a weak numerical response. Finally, the stoat (Mustela erminea) is the most specialized predator and the only one with a clearly delayed numerical response. According to their specific functional and numerical responses, each predator plays a key role at some point of the Lemming cycle, but only the stoat has the potential to drive the Lemming cycle. Stoat predation is greatly reduced in the winter preceding the Lemming peak, and it reaches a maximum in the winter preceding the lowest Lemming summer density. Stoat predation appears to maintain low Lemming densities for at least two successive years. Our study provides empirical support for the specialist predator hypothesis about small mammal population cycles.

  • Functional and numerical responses of four Lemming predators in high arctic Greenland
    Oikos, 2006
    Co-Authors: Olivier Gilg, Benoît Sittler, Brigitte Sabard, Arnaud Hurstel, Raphaël Sané, Pierre Delattre, Ilkka Hanski
    Abstract:

    Gilg, O., Sittler, B., Sabard, B., Hurstel, A., Sane, R., Delattre, P. and Hanski, I. 2006. Functional and numerical responses of four Lemming predators in high arctic Greenland. - Oikos 113: 193-216. The high-arctic tundra ecosystem has the world's simplest vertebrate predator-prey community, with only four predators preying upon one rodent species, the collared Lemming {Dicrostonyx groenlandicus). We document the functional and numerical responses of all the four predators in NE Greenland. Using these data, we assess the impact of predation on the dynamics of the collared Lemming with a 4 yr cycle and > 100-fold difference between maximum and minimum densities. All predator species feed mostly ( >90%) on Lemmings when Lemming density is > 1 ha~ \ but the shapes of the predators' responses vary greatly. The snowy owl (Nyctea scandiaca) is present and breeds only when Lemming densities at snowmelt are >2 ha~ \ giving rise to a step-like numerical response. The long- tailed skua {Stercorarius longicaudus) has a type III functional response and shifts from alternate food (mainly berries and insects) to Lemmings with increasing Lemming density. The skua surpasses all the other predators in summer by its total response. The type III functional response of the Arctic fox (Alopex lagopus) starts to increase at much lower Lemming densities than the responses of the avian predators, but it has only a weak numerical response. Finally, the stoat (Mustela erminea) is the most specialized predator and the only one with a clearly delayed numerical response. According to their specific functional and numerical responses, each predator plays a key role at some point of the Lemming cycle, but only the stoat has the potential to drive the Lemming cycle. Stoat predation is greatly reduced in the winter preceding the Lemming peak, and it reaches a maximum in the winter preceding the lowest Lemming summer density. Stoat predation appears to maintain low Lemming densities for at least two successive years. Our study provides empirical support for the specialist predator hypothesis about small mammal population cycles

Gilles Gauthier - One of the best experts on this subject based on the ideXlab platform.

  • Documenting Lemming population change in the Arctic: Can we detect trends?
    Ambio, 2019
    Co-Authors: Dorothée Ehrich, Anders Angerbjörn, Gilles Gauthier, Ray T. Alisauskas, Nina E. Eide, Niels Martin Schmidt, Karin Clark, Frauke Ecke, Erik Framstad, Jay Frandsen
    Abstract:

    Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of Lemming monitoring and research activities, and assess recent trends in Lemming abundance across the circumpolar Arctic. Since 2000, Lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that Lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective.

  • Snow physical properties may be a significant determinant of Lemming population dynamics in the high Arctic
    Arctic Science, 2018
    Co-Authors: Florent Domine, Dominique Fauteux, Vincent Vionnet, Gilles Gauthier, Marie Dumont, Mathieu Barrere
    Abstract:

    Cyclic population fluctuations are common in boreal and Arctic species but the causes of these cycles are still debated today. Among these species, Lemmings are Arctic rodents that live and reproduce under the snow and whose large cyclical population fluctuations in the high Arctic impact the whole tundra food web. We explore, using Lemming population data and snow modeling, whether the hardness of the basal layer of the snow-pack, determined by rain-on-snow events (ROS) and wind storms in autumn, can affect brown Lemming population dynamics in the Canadian high Arctic. Using a 7-year dataset collected on Bylot Island, Nunavut, Canada over the period 2003-2014, we demonstrate that liquid water input to snow is strongly inversely related with winter population growth (R 2 ≥ 0.62) and to a lesser extent to Lemming summer densities and winter nest densities (R 2 = 0.29-0.39). ROS in autumn can therefore influence the amplitude of brown Lemming population fluctuations. Increase in ROS events with climate warming should strongly impact the populations of Lemmings and consequently those of the many predators that depend upon them. Snow conditions may be a key factor influencing the cyclic dynamics of Arctic animal populations. Résumé : Des fluctuations cycliques de population sont fréquentes chez des espèces boréales et arctiques mais les causes de ces cycles sont encore débattues. Parmi ces espèces, les Lemmings sont des rongeurs arctiques qui vivent et se reproduisent sous la neige et dont les grandes variations de population cycliques dans le haut-arctique impac-tent tout le réseau trophique toundrique. Au moyen de données sur les populations de Lemming et de modélisation de la neige, nous examinons la possibilité que la dureté de la couche de neige basale, déterminée par des évènements de pluie sur neige (PSN) et

  • snow physical properties may be a significant determinant of Lemming population dynamics in the high arctic
    Arctic Science, 2018
    Co-Authors: Florent Domine, Dominique Fauteux, Vincent Vionnet, Gilles Gauthier, Marie Dumont, Mathieu Barrere
    Abstract:

    Cyclic population fluctuations are common in boreal and Arctic species but the causes of these cycles are still debated today. Among these species, Lemmings are Arctic rodents that live and reproduce under the snow and whose large cyclical population fluctuations in the high Arctic impact the whole tundra food web. We explore, using Lemming population data and snow modeling, whether the hardness of the basal layer of the snowpack, determined by rain-on-snow events (ROS) and wind storms in autumn, can affect brown Lemming population dynamics in the Canadian high Arctic. Using a 7-year dataset collected on Bylot Island, Nunavut, Canada over the period 2003–2014, we demonstrate that liquid water input to snow is strongly inversely related with winter population growth (R2 ≥ 0.62) and to a lesser extent to Lemming summer densities and winter nest densities (R2 = 0.29–0.39). ROS in autumn can therefore influence the amplitude of brown Lemming population fluctuations. Increase in ROS events with climate warming...

  • POPULATION ECOLOGY- ORIGINAL RESEARCH The effect of snow cover on Lemming population cycles in the Canadian High Arctic
    2016
    Co-Authors: Gilles Gauthier, Dominique Berteaux
    Abstract:

    Abstract Rising temperatures and changes in the pre-cipitation regime will have a strong impact on the quality of the snow cover in the Arctic. A snow cover of good quality protecting Lemmings from cold temperatures and predators is thought to be an important factor for main-taining the cyclic dynamic of their populations in the tundra. We examined if the characteristics of annual fluc-tuations (amplitude and shape of phases) in brown lem-ming (Lemmus trimucronatus) density could be determined by snow depth, snow density, sub-nivean temperature and persistence of snow. Using an 18-year time series of brown Lemming abundance on Bylot Island in the Canadian Arc-tic, we tested if snow variables could explain the residual variation between the observed Lemming density and the one predicted by models where cyclicity had been accounted for. Our analysis provides support for the hypothesis that snow cover can affect the amplitude and possibly also the periodicity of Lemming population cycles in the High Arctic. Summer abundance of brown Lemmings was higher following winters with a deep snow cover and a low-density snow pack near the ground but was unaffected by the date of establishment or melting and duration of the snow cover. Two snow variables showed a temporal trend; mean winter snow depth tended to increase and date of establishment of the hiemal threshold occurred earlier over time. These temporal trends, which should be favourable to Lemmings, may explain why healthy population cycles have apparently been maintained at our study site contrary to other Arctic sites

  • highly overlapping winter diet in two sympatric Lemming species revealed by dna metabarcoding
    PLOS ONE, 2015
    Co-Authors: Eeva M. Soininen, Frédéric Bilodeau, Gilles Gauthier, Dominique Berteaux, Ludovic Gielly, Eva Bellemain, Galina Gussarova, Kristian Hassel, Pierre Taberlet, Hans K Stenoien
    Abstract:

    Sympatric species are expected to minimize competition by partitioning resources, especially when these are limited. Herbivores inhabiting the High Arctic in winter are a prime example of a situation where food availability is anticipated to be low, and thus reduced diet overlap is expected. We present here the first assessment of diet overlap of high arctic Lemmings during winter based on DNA metabarcoding of feces. In contrast to previous analyses based on microhistology, we found that the diets of both collared (Dicrostonyx groenlandicus) and brown Lemmings (Lemmus trimucronatus) on Bylot Island were dominated by Salix while mosses, which were significantly consumed only by the brown Lemming, were a relatively minor food item. The most abundant plant taxon, Cassiope tetragona, which alone composes more than 50% of the available plant biomass, was not detected in feces and can thus be considered to be non-food. Most plant taxa that were identified as food items were consumed in proportion to their availability and none were clearly selected for. The resulting high diet overlap, together with a lack of habitat segregation, indicates a high potential for resource competition between the two Lemming species. However, Salix is abundant in the winter habitats of Lemmings on Bylot Island and the non-Salix portion of the diets differed between the two species. Also, Lemming grazing impact on vegetation during winter in the study area is negligible. Hence, it seems likely that the high potential for resource competition predicted between these two species did not translate into actual competition. This illustrates that even in environments with low primary productivity food resources do not necessarily generate strong competition among herbivores.

Benoît Sittler - One of the best experts on this subject based on the ideXlab platform.

  • Are gastrointestinal parasites associated with the cyclic population dynamics of their arctic Lemming hosts?
    International Journal for Parasitology: Parasites and Wildlife, 2019
    Co-Authors: Olivier Gilg, Benoît Sittler, Niels Martin Schmidt, Loïc Bollache, Eve Afonso, Glenn Yannic, Lars Holst Hansen, Jannik Hansen, Johannes Lang, Nicolas Meyer
    Abstract:

    Many rodents, including most populations of arctic Lemmings (genus Dicrostonyx and Lemmus), have cyclic population dynamics. Among the numerous hypotheses which have been proposed and tested to explain this typical characteristic of some terrestrial vertebrate communities, trophic interactions have often been presented as the most likely drivers of these periodic fluctuations. The possible role of parasites has, however, only seldom been assessed. In this study, we genetically measured the prevalence of two endoparasite taxa, eimerians and cestodes, in 372 faecal samples from collared Lemmings, over a five year period and across three distant sites in Northeast Greenland. Prevalence of cestodes was low (2.7% over all sites and years) and this taxon was only found at one site (although in 4 out of 5 years) in adult hosts. By contrast, we found high prevalence for eimerians (77.7% over all sites and years), which occurred at all sites, in every year, for both age classes (at the Hochstetter Forland site where both adult and juvenile faeces were collected) and regardless of reproductive and social status inferred from the characteristics of the Lemming nests where the samples had been collected. Prevalence of eimerians significantly varied among years (not among sites) and was higher for juvenile than for adult Lemmings at the Hochstetter Forland site. However, higher prevalence of eimerians (P t ) was only associated with lower Lemming density (N t ) at one of the three sites and we found no delayed density dependence between N t and P t+1 to support the parasite hypothesis. Our results show that there is no clear relation between Lemming density and eimerian faecal prevalence in Northeast Greenland and hence no evidence that eimerians could be driving the cyclic population dynamics of collared Lemmings in this region.

  • Demographic responses of a site-faithful and territorial predator to its fluctuating prey: long-tailed skuas and arctic Lemmings.
    Journal of Animal Ecology, 2014
    Co-Authors: Frederic Barraquand, Benoît Sittler, Olivier Gilg, John-andré Henden, Toke T. Høye, Nigel G. Yoccoz, Niels M. Schmidt, Rolf A. Ims
    Abstract:

    Environmental variability, through interannual variation in food availability or climatic variables, is usually detrimental to population growth. It can even select for constancy in key life-history traits, though some exceptions are known. Changes in the level of environmental variability are therefore important to predict population growth or life-history evolution. Recently, several cyclic vole and Lemming populations have shown large dynamical changes that might affect the demography or life-histories of rodent predators. Skuas constitute an important case study among rodent predators, because of their strongly saturating breeding productivity (they lay only two eggs) and high degree of site fidelity, in which they differ from nomadic predators raising large broods in good rodent years. This suggests that they cannot capitalize on Lemming peaks to the same extent as nomadic predators and might be more vulnerable to collapses of rodent cycles. We develop a model for the population dynamics of long-tailed skuas feeding on Lemmings to assess the demographic consequences of such variable and non-stationary prey dynamics, based on data collected in NE Greenland. The model shows that populations of long-tailed skua sustain well changes in Lemming dynamics, including temporary collapses (e.g. 10 years). A high floater-to-breeder ratio emerges from rigid territorial behaviour and a long-life expectancy, which buffers the impact of adult abundance's decrease on the population reproductive output. The size of the floater compartment is affected by changes in both mean and coefficient of variation of Lemming densities (but not cycle amplitude and periodicity per se). In Greenland, the average Lemming density is below the threshold density required for successful breeding (including during normally cyclic periods). Due to Jensen's inequality, skuas therefore benefit from Lemming variability; a positive effect of environmental variation. Long-tailed skua populations are strongly adapted to fluctuating Lemming populations, an instance of demographic lability in the reproduction rate. They are also little affected by poor Lemming periods, if there are enough floaters, or juveniles disperse to neighbouring populations. The status of Greenland skua populations therefore strongly depends upon floater numbers and juvenile movements, which are not known. This reveals a need to intensify colour-ringing efforts on the long-tailed skua at a circumpolar scale.

  • SUPPORTING ONLINE MATERIAL Cyclic dynamics in a simple vertebrate predator-prey community
    2014
    Co-Authors: Olivier Gilg, Ilkka Hanski, Benoît Sittler
    Abstract:

    In our model (main article), the numbers of Lemmings predated by the arctic fox, the long-tailed skua and the snowy owl were calculated based on the functional and numerical responses of the predators presented in Fig. 1 (main article). All these species feed mostly on Lemmings, which account for>90 % of their diet when Lemming densities are>1 ind./ha. At lower Lemming densities, the main alternate prey are birds (ptarmigan, waders and passerines) for the snowy owl, small birds, fishes, invertebrates and berries for the long-tailed skua, and arctic hare, muskox carrion, birds, eggs, invertebrates and berries for the arctic fox (O. Gilg et al. in prep.). Below, we present a more detailed description of the methods used to calculate (i) the functional and (ii) numerical responses of these predators to the Lemming density, (iii) the fieldestimated parameter values (Table S1), and (iv) how we implemented the numerical responses in the model (the functional responses were simply added to the prey equation as presented in the main article). Additionally, we describe (v) how we estimated the Lemming density at snowmelt (N’) based on the density of winter nests for 1988-2002 and on direct live-trapping for 1998-2002. We present (vi) the empirical support for lack of space or food limitation in Lemming dynamics. W

  • Functional and numerical responses of four Lemming predators in high arctic Greenland.
    Oikos, 2006
    Co-Authors: Olivier Gilg, Benoît Sittler, Brigitte Sabard, Arnaud Hurstel, Raphaël Sané, Pierre Delattre, Ilkka Hanski
    Abstract:

    The high-arctic tundra ecosystem has the world's simplest vertebrate predator-/prey community, with only four predators preying upon one rodent species, the collared Lemming (Dicrostonyx groenlandicus ). We document the functional and numerical responses of all the four predators in NE Greenland. Using these data, we assess the impact of predation on the dynamics of the collared Lemming with a 4 yr cycle and >100-fold difference between maximum and minimum densities. All predator species feed mostly (>90%) on Lemmings when Lemming density is >1 ha-1, but the shapes of the predators' responses vary greatly. The snowy owl (Nyctea scandiaca) is present and breeds only when Lemming densities at snowmelt are >2 ha-1, giving rise to a step-like numerical response. The long-tailed skua (Stercorarius longicaudus ) has a type III functional response and shifts from alternate food (mainly berries and insects) to Lemmings with increasing Lemming density. The skua surpasses all the other predators in summer by its total response. The type III functional response of the Arctic fox (Alopex lagopus ) starts to increase at much lower Lemming densities than the responses of the avian predators, but it has only a weak numerical response. Finally, the stoat (Mustela erminea) is the most specialized predator and the only one with a clearly delayed numerical response. According to their specific functional and numerical responses, each predator plays a key role at some point of the Lemming cycle, but only the stoat has the potential to drive the Lemming cycle. Stoat predation is greatly reduced in the winter preceding the Lemming peak, and it reaches a maximum in the winter preceding the lowest Lemming summer density. Stoat predation appears to maintain low Lemming densities for at least two successive years. Our study provides empirical support for the specialist predator hypothesis about small mammal population cycles.

  • Functional and numerical responses of four Lemming predators in high arctic Greenland
    Oikos, 2006
    Co-Authors: Olivier Gilg, Benoît Sittler, Brigitte Sabard, Arnaud Hurstel, Raphaël Sané, Pierre Delattre, Ilkka Hanski
    Abstract:

    Gilg, O., Sittler, B., Sabard, B., Hurstel, A., Sane, R., Delattre, P. and Hanski, I. 2006. Functional and numerical responses of four Lemming predators in high arctic Greenland. - Oikos 113: 193-216. The high-arctic tundra ecosystem has the world's simplest vertebrate predator-prey community, with only four predators preying upon one rodent species, the collared Lemming {Dicrostonyx groenlandicus). We document the functional and numerical responses of all the four predators in NE Greenland. Using these data, we assess the impact of predation on the dynamics of the collared Lemming with a 4 yr cycle and > 100-fold difference between maximum and minimum densities. All predator species feed mostly ( >90%) on Lemmings when Lemming density is > 1 ha~ \ but the shapes of the predators' responses vary greatly. The snowy owl (Nyctea scandiaca) is present and breeds only when Lemming densities at snowmelt are >2 ha~ \ giving rise to a step-like numerical response. The long- tailed skua {Stercorarius longicaudus) has a type III functional response and shifts from alternate food (mainly berries and insects) to Lemmings with increasing Lemming density. The skua surpasses all the other predators in summer by its total response. The type III functional response of the Arctic fox (Alopex lagopus) starts to increase at much lower Lemming densities than the responses of the avian predators, but it has only a weak numerical response. Finally, the stoat (Mustela erminea) is the most specialized predator and the only one with a clearly delayed numerical response. According to their specific functional and numerical responses, each predator plays a key role at some point of the Lemming cycle, but only the stoat has the potential to drive the Lemming cycle. Stoat predation is greatly reduced in the winter preceding the Lemming peak, and it reaches a maximum in the winter preceding the lowest Lemming summer density. Stoat predation appears to maintain low Lemming densities for at least two successive years. Our study provides empirical support for the specialist predator hypothesis about small mammal population cycles

Ilkka Hanski - One of the best experts on this subject based on the ideXlab platform.

  • SUPPORTING ONLINE MATERIAL Cyclic dynamics in a simple vertebrate predator-prey community
    2014
    Co-Authors: Olivier Gilg, Ilkka Hanski, Benoît Sittler
    Abstract:

    In our model (main article), the numbers of Lemmings predated by the arctic fox, the long-tailed skua and the snowy owl were calculated based on the functional and numerical responses of the predators presented in Fig. 1 (main article). All these species feed mostly on Lemmings, which account for>90 % of their diet when Lemming densities are>1 ind./ha. At lower Lemming densities, the main alternate prey are birds (ptarmigan, waders and passerines) for the snowy owl, small birds, fishes, invertebrates and berries for the long-tailed skua, and arctic hare, muskox carrion, birds, eggs, invertebrates and berries for the arctic fox (O. Gilg et al. in prep.). Below, we present a more detailed description of the methods used to calculate (i) the functional and (ii) numerical responses of these predators to the Lemming density, (iii) the fieldestimated parameter values (Table S1), and (iv) how we implemented the numerical responses in the model (the functional responses were simply added to the prey equation as presented in the main article). Additionally, we describe (v) how we estimated the Lemming density at snowmelt (N’) based on the density of winter nests for 1988-2002 and on direct live-trapping for 1998-2002. We present (vi) the empirical support for lack of space or food limitation in Lemming dynamics. W

  • Functional and numerical responses of four Lemming predators in high arctic Greenland.
    Oikos, 2006
    Co-Authors: Olivier Gilg, Benoît Sittler, Brigitte Sabard, Arnaud Hurstel, Raphaël Sané, Pierre Delattre, Ilkka Hanski
    Abstract:

    The high-arctic tundra ecosystem has the world's simplest vertebrate predator-/prey community, with only four predators preying upon one rodent species, the collared Lemming (Dicrostonyx groenlandicus ). We document the functional and numerical responses of all the four predators in NE Greenland. Using these data, we assess the impact of predation on the dynamics of the collared Lemming with a 4 yr cycle and >100-fold difference between maximum and minimum densities. All predator species feed mostly (>90%) on Lemmings when Lemming density is >1 ha-1, but the shapes of the predators' responses vary greatly. The snowy owl (Nyctea scandiaca) is present and breeds only when Lemming densities at snowmelt are >2 ha-1, giving rise to a step-like numerical response. The long-tailed skua (Stercorarius longicaudus ) has a type III functional response and shifts from alternate food (mainly berries and insects) to Lemmings with increasing Lemming density. The skua surpasses all the other predators in summer by its total response. The type III functional response of the Arctic fox (Alopex lagopus ) starts to increase at much lower Lemming densities than the responses of the avian predators, but it has only a weak numerical response. Finally, the stoat (Mustela erminea) is the most specialized predator and the only one with a clearly delayed numerical response. According to their specific functional and numerical responses, each predator plays a key role at some point of the Lemming cycle, but only the stoat has the potential to drive the Lemming cycle. Stoat predation is greatly reduced in the winter preceding the Lemming peak, and it reaches a maximum in the winter preceding the lowest Lemming summer density. Stoat predation appears to maintain low Lemming densities for at least two successive years. Our study provides empirical support for the specialist predator hypothesis about small mammal population cycles.

  • Functional and numerical responses of four Lemming predators in high arctic Greenland
    Oikos, 2006
    Co-Authors: Olivier Gilg, Benoît Sittler, Brigitte Sabard, Arnaud Hurstel, Raphaël Sané, Pierre Delattre, Ilkka Hanski
    Abstract:

    Gilg, O., Sittler, B., Sabard, B., Hurstel, A., Sane, R., Delattre, P. and Hanski, I. 2006. Functional and numerical responses of four Lemming predators in high arctic Greenland. - Oikos 113: 193-216. The high-arctic tundra ecosystem has the world's simplest vertebrate predator-prey community, with only four predators preying upon one rodent species, the collared Lemming {Dicrostonyx groenlandicus). We document the functional and numerical responses of all the four predators in NE Greenland. Using these data, we assess the impact of predation on the dynamics of the collared Lemming with a 4 yr cycle and > 100-fold difference between maximum and minimum densities. All predator species feed mostly ( >90%) on Lemmings when Lemming density is > 1 ha~ \ but the shapes of the predators' responses vary greatly. The snowy owl (Nyctea scandiaca) is present and breeds only when Lemming densities at snowmelt are >2 ha~ \ giving rise to a step-like numerical response. The long- tailed skua {Stercorarius longicaudus) has a type III functional response and shifts from alternate food (mainly berries and insects) to Lemmings with increasing Lemming density. The skua surpasses all the other predators in summer by its total response. The type III functional response of the Arctic fox (Alopex lagopus) starts to increase at much lower Lemming densities than the responses of the avian predators, but it has only a weak numerical response. Finally, the stoat (Mustela erminea) is the most specialized predator and the only one with a clearly delayed numerical response. According to their specific functional and numerical responses, each predator plays a key role at some point of the Lemming cycle, but only the stoat has the potential to drive the Lemming cycle. Stoat predation is greatly reduced in the winter preceding the Lemming peak, and it reaches a maximum in the winter preceding the lowest Lemming summer density. Stoat predation appears to maintain low Lemming densities for at least two successive years. Our study provides empirical support for the specialist predator hypothesis about small mammal population cycles

  • Cyclic Dynamics in a Simple Vertebrate Predator-Prey Community
    Science, 2003
    Co-Authors: Olivier Gilg, Ilkka Hanski, Benoît Sittler
    Abstract:

    The collared Lemming in the high-Arctic tundra in Greenland is preyed upon by four species of predators that show marked differences in the numbers of Lemmings each consumes and in the dependence of their dynamics on Lemming density. A predatorprey model based on the field-estimated predator responses robustly predicts 4-year periodicity in Lemming dynamics, in agreement with long-term empirical data. There is no indication in the field that food or space limits Lemming population growth, nor is there need in the model to consider those factors. The cyclic dynamics are driven by a 1-year delay in the numerical response of the stoat and stabilized by strongly density-dependent predation by the arctic fox, the snowy owl, and the long-tailed skua.

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  • POPULATION ECOLOGY- ORIGINAL RESEARCH The effect of snow cover on Lemming population cycles in the Canadian High Arctic
    2016
    Co-Authors: Gilles Gauthier, Dominique Berteaux
    Abstract:

    Abstract Rising temperatures and changes in the pre-cipitation regime will have a strong impact on the quality of the snow cover in the Arctic. A snow cover of good quality protecting Lemmings from cold temperatures and predators is thought to be an important factor for main-taining the cyclic dynamic of their populations in the tundra. We examined if the characteristics of annual fluc-tuations (amplitude and shape of phases) in brown lem-ming (Lemmus trimucronatus) density could be determined by snow depth, snow density, sub-nivean temperature and persistence of snow. Using an 18-year time series of brown Lemming abundance on Bylot Island in the Canadian Arc-tic, we tested if snow variables could explain the residual variation between the observed Lemming density and the one predicted by models where cyclicity had been accounted for. Our analysis provides support for the hypothesis that snow cover can affect the amplitude and possibly also the periodicity of Lemming population cycles in the High Arctic. Summer abundance of brown Lemmings was higher following winters with a deep snow cover and a low-density snow pack near the ground but was unaffected by the date of establishment or melting and duration of the snow cover. Two snow variables showed a temporal trend; mean winter snow depth tended to increase and date of establishment of the hiemal threshold occurred earlier over time. These temporal trends, which should be favourable to Lemmings, may explain why healthy population cycles have apparently been maintained at our study site contrary to other Arctic sites

  • highly overlapping winter diet in two sympatric Lemming species revealed by dna metabarcoding
    PLOS ONE, 2015
    Co-Authors: Eeva M. Soininen, Frédéric Bilodeau, Gilles Gauthier, Dominique Berteaux, Ludovic Gielly, Eva Bellemain, Galina Gussarova, Kristian Hassel, Pierre Taberlet, Hans K Stenoien
    Abstract:

    Sympatric species are expected to minimize competition by partitioning resources, especially when these are limited. Herbivores inhabiting the High Arctic in winter are a prime example of a situation where food availability is anticipated to be low, and thus reduced diet overlap is expected. We present here the first assessment of diet overlap of high arctic Lemmings during winter based on DNA metabarcoding of feces. In contrast to previous analyses based on microhistology, we found that the diets of both collared (Dicrostonyx groenlandicus) and brown Lemmings (Lemmus trimucronatus) on Bylot Island were dominated by Salix while mosses, which were significantly consumed only by the brown Lemming, were a relatively minor food item. The most abundant plant taxon, Cassiope tetragona, which alone composes more than 50% of the available plant biomass, was not detected in feces and can thus be considered to be non-food. Most plant taxa that were identified as food items were consumed in proportion to their availability and none were clearly selected for. The resulting high diet overlap, together with a lack of habitat segregation, indicates a high potential for resource competition between the two Lemming species. However, Salix is abundant in the winter habitats of Lemmings on Bylot Island and the non-Salix portion of the diets differed between the two species. Also, Lemming grazing impact on vegetation during winter in the study area is negligible. Hence, it seems likely that the high potential for resource competition predicted between these two species did not translate into actual competition. This illustrates that even in environments with low primary productivity food resources do not necessarily generate strong competition among herbivores.

  • Does Lemming winter grazing impact vegetation in the Canadian Arctic?
    Polar Biology, 2014
    Co-Authors: Frédéric Bilodeau, Dominique Fauteux, Gilles Gauthier, Dominique Berteaux
    Abstract:

    In low-productivity environments such as the tundra, it has been proposed that regular, multi-annual population cycles of Lemmings could be driven by winter food depletion in years of peak abundance. If Lemming population dynamics is controlled by food resources, we predict that (1) winter grazing should negatively impact the abundance of food plants, (2) this impact should be proportional to Lemming density and (3) high Lemming winter grazing pressure should result in reduced plant growth during the following summer. We tested these predictions on Bylot Island, Nunavut, Canada, where two species of Lemmings are present: the brown ( Lemmus trimucronatus ) and collared Lemming ( Dicrostonyx groenlandicus ). We installed 16 exclosures in their preferred wintering habitat (snowbeds) and annually sampled plant biomass inside and outside exclosures at snow melt and at peak growth during the summers of 2009–2012, covering a full population cycle. Winter grazing had no impact on total vascular plant or moss biomass at snow melt in all years. Among plant families, only Caryophyllaceae, which was uncommon, showed a decline. In moss taxa, a negative effect was found on Polytrichum in only 1 year out of three. Overall, plant regrowth during the subsequent summer showed annual variation and tended to be reduced in the 2 years of high Lemming abundance. However, this could be a consequence of summer grazing. Overall, the impact of Lemming winter grazing on plants was weak and short-lived, even in years of high Lemming abundance. Therefore, our results are not consistent with the hypothesis that food depletion during winter was the cause of the Lemming decline following peak abundance at our study site. Other factors may limit Lemming populations and prevent them from reaching densities high enough to exhaust their food resources.

  • The effect of snow cover on Lemming population cycles in the Canadian High Arctic
    Oecologia, 2013
    Co-Authors: Frédéric Bilodeau, Gilles Gauthier, Dominique Berteaux
    Abstract:

    Rising temperatures and changes in the precipitation regime will have a strong impact on the quality of the snow cover in the Arctic. A snow cover of good quality protecting Lemmings from cold temperatures and predators is thought to be an important factor for maintaining the cyclic dynamic of their populations in the tundra. We examined if the characteristics of annual fluctuations (amplitude and shape of phases) in brown Lemming ( Lemmus trimucronatus ) density could be determined by snow depth, snow density, sub-nivean temperature and persistence of snow. Using an 18-year time series of brown Lemming abundance on Bylot Island in the Canadian Arctic, we tested if snow variables could explain the residual variation between the observed Lemming density and the one predicted by models where cyclicity had been accounted for. Our analysis provides support for the hypothesis that snow cover can affect the amplitude and possibly also the periodicity of Lemming population cycles in the High Arctic. Summer abundance of brown Lemmings was higher following winters with a deep snow cover and a low-density snow pack near the ground but was unaffected by the date of establishment or melting and duration of the snow cover. Two snow variables showed a temporal trend; mean winter snow depth tended to increase and date of establishment of the hiemal threshold occurred earlier over time. These temporal trends, which should be favourable to Lemmings, may explain why healthy population cycles have apparently been maintained at our study site contrary to other Arctic sites.

  • disentangling trophic relationships in a high arctic tundra ecosystem through food web modeling
    Ecology, 2012
    Co-Authors: Pierre Legagneux, Frédéric Bilodeau, Gilles Gauthier, Dominique Berteaux, Joel Bety, Mariechristine Cadieux, E Bolduc, Laura Mckinnon, A Tarroux, Jeanfrancois Therrien
    Abstract:

    Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator-prey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric Lemming species (brown and collared Lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that ,10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on Lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with Lemming abundance. Predation of collared Lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown Lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of allochthonous resources subsidizing top predators and the absence of large herbivores may partly explain the predominant role of predation in this low-productivity ecosystem.