It is currently unclear how Toxoplasma gondii (Nicolle and Manceaux, 1908) persists in arctic tundra ecosystems in the absence of felid definitive hosts. To investigate potential transmission routes of T. gondii in a terrestrial arctic food web, we collected samples from two migratory herbivores, Ross's Geese (Chen rossi (Cassin, 1861)) and Lesser Snow Geese (Chen caerulescens (L., 1758)), and from two resident herbivores, Nearctic brown lemmings (Lemmus trimucronatus (Richardson, 1825)) and collared lemmings (Dicrostonyx groenlandicus (Traill, 1823)), trapped at Karrak Lake, Nunavut, Canada. Antibodies were detected in 76 of 234 (32.4%) serum samples from Ross's Geese and 66 of 233(28.3%) serum samples from Lesser Snow Geese. We did not detect T. gondii antibodies in filter-paper eluate tested from thoracic fluid samples collected from 84 lemmings. We did not detect T. gamin DNA in brain tissue from these lemmings. Although a small sample size, our findings suggest that lemmings in this terrestrial arctic ecosystem are not exposed to, or infected with, the parasite. This suggests that oocysts are not introduced into the terrestrial arctic ecosystem at Karrak Lake via freshwater runoff from temperate regions. This study demonstrated that live adult arcticnesting geese are exposed to T. gamin and therefore migratory herbivorous hosts are potential sources of T. gondii infection for predators in terrestrial arctic ecosystems.

Cardiovascular adaptations that permit successful exploitation of polar marine waters by fish requires a capacity to negate or compensate for the depressive effects of low temperatures on physiological processes. Here, we examined the effects of acute and chronic temperature change on the maximum cardiac performance of shorthorn sculpin (Myoxocephalus scorpius (L., 1758)) captured above the Arctic Circle. Our aim was to establish if the sculpin’s success at low temperatures was achieved through thermal independence of cardiac function or via thermal compensation as a result of acclimation. Maximum cardiac performance was assessed at both 1 and 6 degrees C with a working perfused heart preparation that was obtained after fish had been acclimated to either 1 or 6 degrees C. Thus, tests were performed at the fish’s acclimation temperature and with an acute temperature change. Maximum cardiac output, which was relatively large (> 50 mL.min(-1).kg(-1) body mass) for a benthic fish at a frigid temperature, was found to be independent of both acclimation temperature and test temperature. While maximum beta-adrenergic stimulation produced positive chronotropy at both acclimation temperatures, inotropic effects were weak or absent. We conclude that thermal independence of cardiac performance at low temperature likely facilitated the exploitation of polar waters by the shorthorn sculpin.

The Swedish Tundra Northwest Expedition of 1999 visited 17 sites throughout the Canadian Arctic. At 12 sites that were intensively sampled we estimated the standing crop of plants and the densities of herbivores and predators with an array of trapping, visual surveys, and faecal-pellet transects. We developed a trophic-balance model using ECOPATH to integrate these observations and determine the fate of primary and secondary production in these tundra ecosystems, which spanned an 8-fold range of standing crop of plants. We estimated that about 13% of net primary production was consumed by herbivores, while over 70% of small-herbivore production was estimated to flow to predators. Only 9% of large-herbivore production was consumed by predators. Organization of Canadian Arctic ecosystems appears to be more top-down than bottom-up. Net primary production does not seem to be herbivore-limited at any site. This is the first attempt to integrate trophic dynamics over the entire Canadian Arctic.

We investigated the selection criteria of moose, Alces alces (L., 1758), feeding on two willow species, Salix phylicifolia L. and Salix myrsinifolia Salisb., and whether these willows respond chemically. We correlated winter twig browsing with the concentrations of primary and secondary plant compounds in twigs and new leaves. Furthermore, we investigated 12 specific phenolics in twigs of S. phylicifolia. During winter, moose browsed twigs with low concentrations of phenolic compounds. Additionally, we found significant negative correlations between browsing and the concentration of 7 of the 12 specific phenolic compounds in S. phylicifolia. Most importantly, even though ours was a field study and had many potential sources of variation, a multivariate analysis revealed that these specific phenolics predicted 47% of the variation in moose browsing. The two willows reacted in different chemical ways to moose browsing, but both showed signs of defensive response in early spring and compensation growth in summer. Our data demonstrate the importance of plant secondary chemicals for feeding behaviour of moose and underline the importance of working at a species level in studies of plant-animal interactions, especially with the chemically heterogeneous willows.

The co-evolved relationship between the chemical composition of plants and herbivory is fundamental in understanding diet selection of herbivores and their impacts on plants and ecosystems. However, the impact of plant secondary chemistry on mammalian herbivory is not fully understood. We investigated seasonal influences of phenolics with low molecular weight (e.g., flavonoids, salicylates) and plant morphology of the tea-leaved willow (Salix phylicifolia L.) on moose (Alces alces (L., 1758)) foraging. We analysed the relationship of different phenolic compounds in twigs and browsing in winter, and in leaves and the degree of leaf stripping in summer, and the role of plant morphology. In winter, higher concentrations of phenolics, e.g., myricetin-related compounds (belonging to the flavonoids), had a negative impact on herbivory by moose. This impact was not associated with a single compound but instead seemed to be more a result of synergistic or additive effects of different compounds. In contrast, the models for summer browsing showed a pronounced effect of plant morphology. Our analyses reveal differences in the relative importance of phenolics of low molecular weight and plant morphology on diet selection between seasons. These findings are relevant for understanding feeding decisions and mechanisms deterring mammalian herbivores known for shaping the vegetation on the ecosystem level.

Differences in body sizes of mountain hares (Lepus timidus L., 1758) and moose (Alces alces (L., 1758)) affect their abilityto perceive and respond to environmental heterogeneity and plant density. Therefore, we expect these species to show nicheseparation at different scales in the same environment. Results showed that the numbers of mountain birches (Betula pubescenssubsp. czerepanovii L.) browsed by moose per unit area was inversely related to hare browsing. Moose browsed larger birchescompared with hares, and while hares targeted areas with high birch densities regardless of tree sizes, moose preferentiallybrowsed areas with high densities of large birches. Moose browsing was clustered at spatial intervals of 1000–1500 m, while harebrowsing was clustered at intervals of less than 500 m. Willows (genus Salix L.) in the study area were heavily browsed by moose,while few observations of hare browsing on willow were made. Regarding both hare and moose, numbers of birch stems withnew browsing per sample plot were positively correlated with the numbers of birch stems with old browsing, indicating thathare and moose preferred the same foraging sites from year to year. These findings have implications for management of thespecies because they show the importance of scale and landscape perspectives in planning and actions.