How landscape dynamics link individual- to population-level movement patterns: a multispecies comparison of ungulate relocation data

Abstract

Aim To demonstrate how the interrelations of individual movements form largescale population-level movement patterns and how these patterns are associated with the underlying landscape dynamics by comparing ungulate movements across species.Locations Arctic tundra in Alaska and Canada, temperate forests in Massachusetts, Patagonian Steppes in Argentina, Eastern Steppes in Mongolia. MethodsWe used relocation data from four ungulate species (barren-ground caribou, Mongolian gazelle, guanaco and moose) to examine individual movements and the interrelation of movements among individuals. We applied and developed a suite of spatial metrics that measure variation in movement among individuals as population dispersion, movement coordination and realized mobility. Taken together, these metrics allowed us to quantify and distinguish among different large-scale population-level movement patterns such as migration, range residency and nomadism. We then related the population-level movement patterns to the underlying landscape vegetation dynamics via long-term remote sensing measurements of the temporal variability, spatial variability and unpredictability of vegetation productivity. ResultsMoose, which remained in sedentary home ranges, and guanacos, which were partially migratory, exhibited relatively short annual movements associated with landscapes having very little broad-scale variability in vegetation. Caribou and gazelle performed extreme long-distance movements that were associated with broad-scale variability in vegetation productivity during the peak of the growing season. Caribou exhibited regular seasonal migration in which individuals were clustered for most of the year and exhibited coordinated movements. In contrast, gazelle were nomadic, as individuals were independently distributed and moved in an uncoordinated manner that relates to the comparatively unpredictable (yet broad-scale) vegetation dynamics of their landscape. Main conclusionsWe show how broad-scale landscape unpredictability may lead to nomadism, an understudied type of long-distance movement. In contrast to classical migration where landscapes may vary at broad scales but in a predictable manner, long-distance movements of nomadic individuals are uncoordinated and independent from other such individuals. Landscapes with little broad-scale variability in vegetation productivity feature smaller-scale movements and allow for range residency. Nomadism requires distinct integrative conservation strategies that facilitate long-distance movements across the entire landscape and are not limited to certain migration corridors.

From Fine-Scale Foraging to Home Ranges: A Semivariance Approach to Identifying Movement Modes across Spatiotemporal Scales

“…These enormous area requirements support conservation concerns over fenced borders and transportation infrastructure such as the Trans-Mongolian Railway that act as barriers to gazelle movement. The range estimate reported in this study is the best estimate of Mongolian gazelle area requirements in the Eastern Steppe to date, as past estimates employ ad hoc home-range estimation methods that ignore autocorrelation in the movement data (see below) and are based on much smaller data sets (Olson et al 2010) or report only annual distance moved (Berger 2004;Ito et al 2006;Mueller et al 2011).…”

Guanaco abundance and monitoring in Southern Patagonia: distance sampling reveals substantially greater numbers than previously reported

“…We think that our distribution of road segments among 2 years of study was suitable considering the logistic and time constraints imposed by the large area to be covered. Moreover, as guanacos exhibit quite sedentary habits and long-distance movements are rare even for migratory individuals (Mueller et al 2011), separation between segments surveyed in different years further ensure independence of observations.…”

Rigorous home range estimation with movement data: a new autocorrelated kernel density estimator

“…2A, C) the 95% home range area of the AKDE is much larger than the MCP would be. Mongolian gazelles are nomadic wanderers whose movements may involve gross displacements exceeding 1000 km/yr with little concordance among years (Olson et al 2010, Mueller et al 2011, Fleming et al 2014b Consequently, longer observation periods tend to show the gazelles using larger amounts of space, up to an asymptote set by the ACF's details (Fleming et al 2014a). The AKDE captures this important behavior, whereas conventional space-use estimates will miss it because they discard the information encoded in the ACF on the movement process' long-run behavior.…”