49 research outputs found
Winter severity modulates the benefits of using a habitat temporally uncoupled from browsing
Resources whose abundance is not affected by the density of the consumer population, namely
donor-controlled resources, are ubiquitous. Donor-controlled resources can act as food subsidies when
they sustain consumer populations at higher densities than what would be predicted without donorcontrolled
dynamics. Herbivore populations that have access to food subsidies may reach and maintain
high densities, with potential major ecological and economic consequences. A better understanding of
the roles of food subsidies on temperate herbivores will likely be achieved by simultaneously taking into
account other drivers of demographic variations such as winter severity. Here, we tested the hypothesis
that the use of a donor-controlled food resource that may act as a food subsidy, namely balsam fir (Abies
balsamea), and winter severity act together to shape the patterns of overwinter mass loss in a large herbivore
population (white-tailed deer, Odocoileus virginianus). We monitored weather conditions, diet, habitat
use, and mass loss of female deer during two highly contrasted winters. During an exceptionally milder
winter, characterized by shallower snow depth and warmer windchill temperatures, female deer shifted
their diet toward resources usually covered by snow during typical winters. Surprisingly, the rate of body
mass loss remained similar during the milder and the harsher winter. The rate of body mass loss rather
decreased with the use of balsam fir stands during the harsher winter, but increased with that same variable
during the milder winter. Our study revealed that deer can alleviate overwinter mass loss by using a
donor-controlled habitat type temporally uncoupled from browsing, but that this benefit is climate dependent.
This study represents an additional step to address the largely unexplored concept of how temporal
uncoupling between resources and consumer dynamics may contribute to sustain consumer populations
at higher densities than predicted without considering donor-controlled dynamics
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Developing common protocols to measure tundra herbivory across spatial scales
Understanding and predicting large-scale ecological responses to global environmental change requires comparative studies across geographic scales with coordinated efforts and standardized methodologies. We designed, applied and assessed standardized protocols to measure tundra herbivory at three spatial scales: plot, site (habitat), and study area (landscape). The plot and site-level protocols were tested in the field during summers 2014-2015 at eleven sites, nine of them comprising warming experimental plots included in the International Tundra Experiment (ITEX). The study area protocols were assessed during 2014-2018 at 24 study areas across the Arctic. Our protocols provide comparable and easy-to-implement methods for assessing the intensity of invertebrate herbivory within ITEX plots and for characterizing vertebrate herbivore communities at larger spatial scales. We discuss methodological constraints and make recommendations for how these protocols can be used and how sampling effort can be optimized to obtain comparable estimates of herbivory, both at ITEX sites and at large landscape scales. The application of these protocols across the tundra biome will allow characterizing and comparing herbivore communities across tundra sites and at ecologically relevant spatial scales, providing an important step towards a better understanding of tundra ecosystem responses to large-scale environmental change.CGB was funded by the Estonian Research Council (grant IUT 20-28), and
the European Regional Development Fund (Centre of Excellence EcolChange). JDMS was supported by the Research
Council of Norway (262064). OG and LB were supported by the French Polar Institute (program â1036
Interactionsâ) and PRC CNRS Russie 396 (program âICCVATâ). DSH, NL, MAG, JB and JDR were supported by the
Natural Sciences and Engineering Research Council (Canada). NL, MAG, JB and JDR were supported by the Polar
Continental Shelf Program. NL was supported by the Canada Research Chair program and the Canada Foundation
for Innovation. NL and JB were supported by Environment Canada and Polar Knowledge Canada. NL and MAG were
supported by the Government of Nunavut, the Igloolik Community, and Université de Moncton. NL, MAG and JB
were supported by the Northern Scientific Training Program. JMA was funded by Carl Tryggers stiftelse för
vetenskaplig forskning and Qatar Petroleum (QUEX-CAS-QP-RD-18_19). IHM-S was funded by the UK Natural
Environmental Research Council Shrub Tundra (NE/M016323/1) grant. ISJ was funded by the University of Iceland
Research Fund. Fieldwork in Yamal peninsula (Erkuta, Sabetta and Belyi) for DE, NS and AS was supported by the
Russian Foundation for Basic Research (No: 18-05-60261 and No: 18-54-15013), Fram Centre project YaES (No:
362259), the Russian Center of Development of the Arctic, and the âYamal-LNGâ company. Fieldwork in UtqiaÄĄvik
was supported by the U.S. Fish and Wildlife Service. Fieldwork in Svalbard was supported by the Norwegian
Research Council (AFG No: 246080/E10), the Norwegian Polar Institute, Climate-ecological Observatory for Arctic
Tundra â COAT, the Svalbard Environmental protection fund (project number 15/20), and the University Centre in
Svalbard (UNIS) and the AB-338/AB-838 students of 2018. Sampling at Billefjorden was supported by GACR 17-
20839S
New avian breeding records for Igloolik Island, Nunavut
New breeding records for three tundra nesting species were documented on the Arctic island of Igloolik (Nunavut, Canada). The species are the Cackling Goose (Branta hutchinsii), the Tundra Swan (Cygnus columbianus), and the Pectoral Sandpiper (Calidris melanotos). These records refine their breeding range in the Canadian Arctic archipelago, while highlighting changes in detected bird communities at specific locations through time
Comment un herbivore surabondant bénéficie des ressources dépendantes, indépendantes ou découplées de la pression de broutement
La pression de broutement des herbivores peut induire des modifications majeures dans les communautĂ©s vĂ©gĂ©tales qui peuvent rĂ©duire lâabondance des ressources alimentaires des herbivores et Ă©ventuellement mener Ă une rĂ©troaction nĂ©gative entre la taille des populations dâherbivores et leur taux de croissance. Une telle boucle de rĂ©troaction peut sâopĂ©rer via une rĂ©duction de la masse corporelle Ă haute densitĂ©, suivie dâune rĂ©duction de la survie et de la reproduction. MalgrĂ© la dĂ©tĂ©rioration persistante des communautĂ©s vĂ©gĂ©tales de lâĂźle dâAnticosti (QuĂ©bec, Canada) suite Ă lâintroduction dâune population de cerf de Virginie en absence de prĂ©dation naturelle, la taille de cette population est demeurĂ©e Ă©levĂ©e durant les derniĂšres dĂ©cennies. Un des mĂ©canismes suggĂ©rĂ©s pour expliquer cette situation est lâutilisation de ressources alimentaires qui seraient indĂ©pendantes ou dĂ©couplĂ©es temporellement de la pression de broutement par le cerf. Deux des ressources consommĂ©es par le cerf Ă lâĂźle dâAnticosti sont considĂ©rĂ©es indĂ©pendantes et dĂ©couplĂ©es temporellement du broutement par le cerf, soit les algues Ă©chouĂ©es et le sapin baumier. Nous avons dĂ©terminĂ© comment la masse corporelle du cerf Ă lâĂźle dâAnticosti est influencĂ©e par les ressources alimentaires dĂ©pendantes, indĂ©pendantes et dĂ©couplĂ©es temporellement du broutement. PremiĂšrement, nous avons dĂ©montrĂ© expĂ©rimentalement que la densitĂ© de cerfs affectait nĂ©gativement lâabondance estivale des herbacĂ©es et arbustes prĂ©fĂ©rĂ©s, qui, en retour, affectait positivement la masse corporelle automnale. DeuxiĂšmement, nous avons dĂ©montrĂ© que la contribution des algues au rĂ©gime alimentaire en dehors de la saison hivernale Ă©tait infĂ©rieure Ă 23% et quâelle nâexpliquait pas les variations de la masse corporelle automnale. La masse corporelle automnale augmentait plutĂŽt avec la contribution de plantes dâhabitat ouvert dans le rĂ©gime alimentaire. TroisiĂšmement, nous avons dĂ©montrĂ© que la perte de masse hivernale diminuait avec lâutilisation des sapiniĂšres durant un hiver rigoureux. Nos travaux permettent de mieux comprendre comment les herbivores surabondants peuvent bĂ©nĂ©ficier des ressources alimentaires affectĂ©es Ă divers degrĂ©s par le broutement. La prochaine Ă©tape serait de dĂ©terminer lâimpact de ces diffĂ©rentes ressources sur le taux de croissance des populations surabondantes dâherbivores.Herbivores can induce major modifications to plant communities that can reduce forage abundance and lead to a retroaction between the size of herbivore populations and their growth rates. Such a feedback loop can be generated by a reduction in body mass at high herbivore density, followed by a reduction in survival and reproduction. Despite the lasting deterioration of plant communities on Anticosti Island (QuĂ©bec, Canada) following the introduction of a white-tailed deer population in absence of natural predation, the size of this population has remained high during the last decades. One of the mechanisms suggested to explain this situation is the use of sources of forage independent or temporally uncoupled from deer browsing pressure. Two types of forage used by deer on Anticosti Island are considered independent or temporally uncoupled from deer browsing, namely drifted seaweed and balsam fir. We determined how body mass of deer on Anticosti Island is influenced by sources of forage that are dependent, independent and temporally uncoupled from deer browsing. First, we demonstrated experimentally that deer density had a negative effect on the summer abundance of preferred forbs and shrubs, which in turn had a positive effect on body mass in the fall. Second, we demonstrated that the contribution of seaweed to diet outside winter was smaller than 23% and did not explain variations in body mass in the fall. Fall body mass rather increased with the contribution of plants from open habitat to diet. Third, we demonstrated that overwinter mass loss decreased with the use of balsam fir stands during a harsh winter. Our findings provide a better understanding of how overabundant herbivores can benefit from sources of forage influenced to varying degrees by browsing. The next step would be to determine the impact of these different resources on the growth rate of overabundant herbivore populations
Effets des ressources allochtones sur une population de renards arctiques Ă l'Ăźle Bylot, Nunavut, Canada
Les flux de nutriments et d'organismes entre les Ă©cosystĂšmes peuvent modifier la
dynamique des populations incluses dans ces systÚmes. Nous avons étudié l'effet de la
consommation d' organismes allochtones sur la productivité d'une population de renard
arctique (Alopex lagopus) Ă l'Ăźle Bylot, Nunavut, Canada. Cette population est incluse dans
un méta-écosystÚme englobant le continent nord américain. En effet, le renard arctique se
nourrit de la grande oie des neiges (Chen caerulescens atlantica), qui migre annuellement
de la cĂŽte est des Ătats-Unis Ă l'Arctique canadien. Nous avons comparĂ© le rĂ©gime
alimentaire estival (2004-2005) et le succĂšs reproducteur (1996-2005) du renard arctique
entre deux secteurs de notre aire d'étude: un secteur situé à proximité d' une grande colonie
d'oies et un secteur qui en Ă©tait Ă©loignĂ© (oĂč les oies sont presque absentes). Puisque le
lemming est reconnu pour influencer la reproduction du renard arctique, nous avons
comparé le succÚs reproducteur du renard entre les différentes phases du cycle de lemming
(pic, déclin, creux). Par l'analyse d' isotopes stables, nous avons démontré que le
pourcentage d'oies dans le régime alimentaire du renard arctique était supérieur dans le
secteur à proximité de la colonie d' oies. Le pourcentage de taniÚres de reproduction était
également supérieur dans le secteur proche de la colonie d'oies, mais plus faible durant les
creux de lemming. La taille de portée était similaire entre les secteurs et les phases du cycle
de lemming. Cette Ă©tude suggĂšre qu' un flux d' organismes transportant des nutriments Ă
l'échelle continentale (oies) peut provoquer l'augmentation de la productivité d'une
population de prédateur (renard arctique). Il serait intéressant de poursuivre cette étude en
estimant les cascades trophiques descendantes pouvant résulter de cet effet des ressources
allochtones sur la productivité du renard arctique