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

Abstract.  The shift in emphasis from single species to ecosystem conservation is revealing how community interactions can potentially influence single species viability and conservation. Although there is much theory and empirical data concerning the dynamic consequences of exploitative interactions, there is still a very poor understanding of the effects of interference interactions. Recent studies, as shown in this review, have documented widespread effects of such interactions among mammalian carnivores. Harassment, loss of kills and intraguild predation have been documented in a wide range of species. The demonstrated effects also include avoidance of larger carnivores in both time and space and reductions in one species density or even total exclusion from certain habitats or regions. Our review of the literature thus provides a range of empirical examples that together demonstrate that these interactions have very important implications on carnivore demography. We believe that the effects of interference might differ strongly from the effects of exploitative competition. This is because interference might have the potential to affect population growth in an inverse density‐dependent manner and thereby also reduce population growth at low densities, therefore increasing extinction probabilities. These factors need to be considered when planning future multi‐species conservation. Further research into the temporal and spatial aspects of co‐existence are required if diverse guilds and communities are to be conserved.

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

Summary1. The loss, fragmentation and degradation of habitat everywhere on Earth prompts increasing attention to identifying landscape features that support animal movement (corridors) or impedes it (barriers). Most algorithms used to predict corridors assume that animals move through preferred habitat either optimally (e.g. least cost path) or as random walkers (e.g. current models), but neither extreme is realistic. 2. We propose that corridors and barriers are two sides of the same coin and that animals experience landscapes as spatiotemporally dynamic corridor-barrier continua connecting (separating) functional areas where individuals fulfil specific ecological processes. Based on this conceptual framework, we propose a novel methodological approach that uses high-resolution individual-based movement data to predict corridor-barrier continua with increased realism. 3. Our approach consists of two innovations. First, we use step selection functions (SSF) to predict friction maps quantifying corridor-barrier continua for tactical steps between consecutive locations. Secondly, we introduce to movement ecology the randomized shortest path algorithm (RSP) which operates on friction maps to predict the corridor-barrier continuum for strategic movements between functional areas. By modulating the parameter Ѳ, which controls the trade-off between exploration and optimal exploitation of the environment, RSP bridges the gap between algorithms assuming optimal movements (when Ѳ approaches infinity, RSP is equivalent to LCP) or random walk (when Ѳ ? 0, RSP ? current models). 4. Using this approach, we identify migration corridors for GPS-monitored wild reindeer (Rangifer t. tarandus) in Norway. We demonstrate that reindeer movement is best predicted by an intermediate value of Ѳ, indicative of a movement trade-off between optimization and exploration. Model calibration allows identification of a corridor-barrier continuum that closely fits empirical data and demonstrates that RSP outperforms models that assume either optimality or random walk. 5. The proposed approach models the multiscale cognitive maps by which animals likely navigate real landscapes and generalizes the most common algorithms for identifying corridors. Because suboptimal, but non-random, movement strategies are likely widespread, our approach has the potential to predict more realistic corridor-barrier continua for a wide range of species.