Abundance, predation, and habitat associations of lemming winter nests in northern Sweden

Abstract

Spatially synchronous fluctuations of animal populations have profound ecological consequences, especially in northern latitudes. Spatially coupled fluctuations are often seen in small rodent populations, albeit with local and regional variations. While both resource limitation and predation influence rodent dynamics, their relative importance for generating spatial variation is less clear, particularly during winter. In this study, we quantify spatial variation in winter abundance of the Norwegian lemming (Lemmus lemmus) across three ecologically connected mountain areas in northern Sweden and evaluate whether the relative strength of bottom‐up and top‐down regulation influences such variation. Our data included observations of predated and nonpredated winter nests as well as environmental characteristics of nest locations and nest predation. While the direction of annual changes in lemming nest abundance was perfectly synchronized among the three areas, there were differences in nest abundance, potentially caused by contrasting amplitudes of temporal fluctuations in lemming winter populations. Mustelid predation was positively associated with decreasing lemming populations but did not differ in occurrence among the three areas. Lemming nests were predominantly observed in meadows, whereas areas prone to flooding and close to the tree line were underrepresented. Mustelid predation was most common close to the tree line, but not associated with geomorphological characteristics related to snow depth. We suggest that the observed differences in lemming winter abundances were caused by variations in the relative strength of bottom‐up and top‐down regulation in the three mountain areas. We encourage further studies evaluating how the relative strength of different processes influence local population regulation, and how such processes influence spatial variation in animal population dynamics at different spatial scales.

Evaluating the use of marine subsidies by Arctic foxes without direct coastal access; insights from stable isotopes

“…The Norwegian lemming generally prefer patches of high productivity (Le Valliant et al 2018). Favourable lemming habitats include meadows in winter (Vigués et al 2022), with a seasonal habitat shift to slightly wetter areas during the summer (Koponen 1970;Henttonen and Kaikusalo 1993). These habitats are generally favourable also for many alpine and sub-Arctic shorebirds (Machin et al 2017), which are the main vectors of marine resources into this terrestrial ecosystem.…”

Properties of vertebrate predator–prey networks in the high Arctic

“…One prominent characteristic of terrestrial northern ecosystems is strong temporal fluctuations in the population sizes of many potential prey species, for example, microtone rodents (Arvicolinae, Krebs et al., 2002) and snowshoe hares ( Lepus americanus , Krebs et al., 2001), as well as large ungulates such as reindeer ( Rangifer tarandus ) and muskoxen ( Ovibus moschatus , Forchhammer et al., 2002). However, such temporal dynamics may not always be synchronized across regional (Angerbjörn et al., 2001) or local scales (Gruyer et al., 2008; Vigués et al., 2022). Such asynchrony can influence both population characteristics (Engen et al., 2002; Gaillard et al., 2000; Heino et al., 1997) and community dynamics (Boutin, 1995) and cause spatial variation in predator–prey interactions (e.g., Dalerum et al., 2018).…”