Restrictions on roaming Until the past century or so, the movement of wild animals was relatively unrestricted, and their travels contributed substantially to ecological processes. As humans have increasingly altered natural habitats, natural animal movements have been restricted. Tucker et al. examined GPS locations for more than 50 species. In general, animal movements were shorter in areas with high human impact, likely owing to changed behaviors and physical limitations. Besides affecting the species themselves, such changes could have wider effects by limiting the movement of nutrients and altering ecological interactions. Science , this issue p. 466

Summary 1.Animal migration has long intrigued scientists and wildlife managers alike, yet migratory species face increasing challenges because of habitat fragmentation, climate change and over-exploitation. Central to the understanding migratory species is the objective discrimination between migratory and nonmigratory individuals in a given population, quantifying the timing, duration and distance of migration and the ability to predict migratory movements. 2. Here, we propose a uniform statistical framework to (i) separate migration from other movement behaviours, (ii) quantify migration parameters without the need for arbitrary cut-off criteria and (iii) test predictability across individuals, time and space. 3. We first validated our novel approach by simulating data based on established theoretical movement patterns. We then formulated the expected shapes of squared displacement patterns as nonlinear models for a suite of movement behaviours to test the ability of our method to distinguish between migratory movement and other movement types. 4. We then tested our approached empirically using 108 wild Global Positioning System (GPS)-collared moose Alces alces in Scandinavia as a study system because they exhibit a wide range of movement behaviours, including resident, migrating and dispersing individuals, within the same population. Applying our approach showed that 87% and 67% of our Swedish and Norwegian subpopulations, respectively, can be classified as migratory. 5. Using nonlinear mixed effects models for all migratory individuals we showed that the distance, timing and duration of migration differed between the sexes and between years, with additional individual differences accounting for a large part of the variation in the distance of migration but not in the timing or duration. Overall, the model explained most of the variation (92%) and also had high predictive power for the same individuals over time (69%) as well as between study populations (74%). 6. The high predictive ability of the approach suggests that it can help increase our understanding of the drivers of migration and could provide key quantitative information for understanding and managing a broad range of migratory species.

Summary 0[ Population size\ calves per female\ female mean age and adult sex ratio of a moose "Alces alces# population in Vefsn\ northern Norway were reconstructed from 0856 to 0882 using cohort analysis and catch!at!age data from 85) "5641# of all individuals harvested[ 1[ The dynamics of the population were in~uenced mainly by density!dependent harvesting\ stochastic variation in climate and intrinsic variation in the age!structure of the female segment of the population[ 2[ A time delay in the assignment of hunting permits in relation to population size increased~uctuations in population size[ 3[ Selective harvesting of calves and yearlings increased the mean age of adult females in the population\ and\ because fecundity in moose is strongly age!speci_c\ the number of calves per female concordantly increased[ However\ after years with high recruit! ment\ the adult mean age decreased as large cohorts entered the adult age!groups[ This age!structure e}ect generated cycles in the rate of recruitment to the population and~uctuations introduced time!lags in the population dynamics[ 4[ An inverse relationship between recruitment rate and population density\ mediated by a density!dependent decrease in female body condition\ could potentially have constituted a regulatory mechanism in the dynamics of the population\ but this e}ect was counteracted by a density!dependent increase in the mean age of adult females[ 5[ Stochastic variation in winter snow depth and summer temperature had delayed e}ects on recruitment rate and in turn population growth rate\ apparently through e}ects on female body condition before conception[ Key!words] cohort analysis\ density dependence\ harvesting\ moose[ Journal of Animal Ecology "0888# 57\ 075Ð193

1999. Body mass and winter mortality in red deer calves: disentangling sex and climate effects, -Ecography 22: 20-30.Understanding population dynamics of large mammals requires studies ol" variation in the age and sex-specific demographic parameters over time and the factors causing this variation. Here, we have focused on the variation in body mass of 8-10-month old red deer calves, in relation to climate and sex over a 20-yr period . We investigated the relationship between body mass and over-winter mortality during 1985 and 1986 and thereby, the phenotypic selection on body mass. We found a high variabihty from year to year in calf body mass. Males were consistently heavier than females. No interaction between sex and year was detected. The body mass of individuals from the same cohort shot during the annual hunting season and snow depth in January each explained ca 20% of the variability in calf body mass. Body mass loss during winter did not differ between sexes, but increased with body mass and varied from year to year. The probability of surviving was strongly related to body mass in each sex. For a given body mass relative to the sex-specific mean, males had a lower probabihty of survival than females. Hence, males had to be 1 kg larger than their mean in order to achieve the same survival as average-sized females. Our results suggested a directional phenotypic selection on body mass that led to an increasing body mass dimorphism in calves. The strength of this selection and the sex difference in the shape of the selection curve may depend, however, on the severity of winter and on sexual dimorphism in body mass at the beginning of winter.A. Loison (unne.loison(alninatr

No abstract

Habitat alteration by humans may change the supply of food and cover for wild ungulates, but few studies have examined how these resources are utilised over time by individuals of different sex and reproductive status. We examined circadian and seasonal variation in habitat utilisation within a moose Alces alces population in central Norway. Our study area covers forests and open habitats, both influenced by human alterations (e.g. forestry and agriculture). We expected moose to select habitats with good forage and cover in all seasons, but to select open foraging habitats mainly during night-time. Moose selected good foraging habitats, such as young forest stands and cultivated land during night, whereas the utilisation of older forest stands providing cover increased during daytime. This circadian pattern changed throughout the year, seemingly related to variation in hours of daylight and provision of forage. Young forest stands provided higher density of preferred food plants compared to older stands and were highly selected from spring until autumn. Relative to young forest, the selection for older forest stands increased towards winter, likely due to provision of higher plant quality late in the growing season, and to reduced accumulation of movement-impeding snow during winter. Selection of cultivated land varied among seasons, being highest when crop biomass was high. We also found some indications of state-dependent habitat selection as reproducing females avoided open, food rich areas in the first months after their calves were born, whereas males and females without young selected these areas in spring and summer. Our results clearly show that moose exploit the variations in cover and food caused by forestry and agriculture. This is particularly relevant for moose in Norway as current changes in forestry practice lead to a reduction in young, food-rich forest stands, possibly aggravating the already declining body conditions and recruitment rates of moose.

Summary 1.Habitats have substantial influence on the distribution and abundance of animals. Animals' selective movement yields their habitat use. Animals generally are more abundant in habitats that are selected most strongly. 2. Models of habitat selection can be used to distribute animals on the landscape or their distribution can be modelled based on data of habitat use, occupancy, intensity of use or counts of animals. When the population is at carrying capacity or in an ideal-free distribution, habitat selection and related metrics of habitat use can be used to estimate abundance. 3. If the population is not at equilibrium, models have the flexibility to incorporate density into models of habitat selection; but abundance might be influenced by factors influencing fitness that are not directly related to habitat thereby compromising the use of habitat-based models for predicting population size. 4. Scale and domain of the sampling frame, both in time and space, are crucial considerations limiting application of these models. Ultimately, identifying reliable models for predicting abundance from habitat data requires an understanding of the mechanisms underlying population regulation and limitation.

To determine the main factors affecting the population dynamics of Svalbard reindeer, we analysed 21 yr of annual censuses, including data on population size, recruitment rate (calves per female) and mortality (number of deaths), from the Reindalen reindeer population. In accordance with previous studies on population dynamics of Svalbard reindeer, we found large inter‐annual variation in population size, mortality and recruitment rates within the study area. Population size decreased in years with low recruitment rate as well as high winter mortality and vice versa. Apparently. the fluctuations were due to both direct density‐dependent food limitation and variation in winter climate associated with high precipitation and icing of the feeding range. We found no delayed density‐dependence or effect of climatic conditions during summer on the population dynamics. The mortality during die‐off years was mainly of calves and very old individuals, indicating that the population was more vulnerable to high die oft in years following high recruitment rate. These results suggest an unstable interaction between the reindeer population and its food supply in these predator‐free environments.