An epizootic of sarcoptic mange was prevalent among Scandinavian red foxes (Vulpes vulpes) during the late 1970s and 1980s. By substantially reducing the population density of foxes, the epizootic created a natural experiment on the importance of fox predation for prey density. The fox population started to recover during the late 1980s. We monitored the populations of the fox and its prey [voles (Cricetidae), mountain hare (Lepus timidus), European hare (L. europaeus), Capercaillie (Tetrao urogallus), Black Grouse (T. tetrix), Hazel Grouse (Bonasa bonasia), and roe deer (Capreolus capreolus)] throughout the event, on a local (101—102 km2), a regional (104 km2), and a national scale. Methods included den counts, snap—trapping, pellet/dropping counts, counts of displaying birds, young/adult ratio from incidental observations of deer, regional questionnaires, and national hunting records. The study revealed red fox predation as a crucial factor in limiting the numbers of hares and grouse as well as fawns per doe of roe deer in autumn, and in conveying the 3—4 yr cyclic fluctuation pattern of voles to small game. The classical view, that predators take but a doomed surplus of their prey, was false for these species in Scandinavia.

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The activity patterns of a coarse browser, the moose. Alces alces, and a selective browser, the roe deer, Capreolus capreolus. in a north boreal forest, central Sweden, were compared with respect to time allocated for foraging and processing (ruminating) in different seasons. Data were quantified by measuring 24 h activity patterns which included both the duration and frequency of active and inactive periods. Activity patterns were measured from 9 female moose and 9 roe deer that were radiomarked during April 1974–May 1978 (roe deer) and February 1982–December 1984 (moose). In total, data were available from 4345 h for roe deer and 14745 h for moose. Roe deer differed from moose in having active bouts more evenly distributed over the day. Generally, both species were most active during sunrise and sunset. Total daily active time varied with season, reaching the highest value in late May – early June among roe deer (56.7% of the day) and a month later among moose (51.9%). Both species were least active in February (30–40%). Average length of active bouts did not differ significantly between the species but changed with season (roe deer 48.6–99.2 min, moose 61.6–88.7 min). Average length of inactive bouts varied significantly with season, with moose having consistently longer bouts (89.3–156.3 min) than roe deer (55.8–107.0 min). The number of activity bouts per day were also higher among roe deer. During midsummer, they changed activity nearly twice as many times as moose (26 times d−1 vs 16 times d−1).

We examined the geographical pattern in growth and adult body size among 14 populations of Swedish moose (Alces alces) using data from 4,294 moose (≥1.5 years old) killed during the hunting season in 1989-1992. In both sexes, adult body mass was significantly positively correlated with latitude. Moose in northern populations had a 15-20% larger adult body mass than moose in the south. Juvenile body mass was correlated with neither latitude nor adult body mass. Thus, variation in time (years) and rate of body growth after the juvenile stage were responsible for most of the variation in adult body mass among populations. Moose in northern populations grew for approximately 2 more years of life than southern moose. In contrast to adult body mass, skeletal size (measured as jawbone length) was not correlated with latitude, suggesting that variation in adult body mass was primarily due to differences in fat reserves. Discrimination between population characteristics, such as moose density, climate, and the amount of browse available to moose, showed climatic harshness to be the most important variable explaining geographical variation in body mass among populations. The results support the notion that in mammals body size increases with latitude in accordance with Bergmann's rule. We conclude that (1) variation in patterns of growth after the juvenile stage is the main cause of the latitudinal trend in adult body size in moose, and (2) climatic conditions are a more important factor than population density and availability of food in explaining geographical variation in growth patterns and adult body mass between populations of Swedish moose.