Variation In Space Use Research Articles

Gag (Mycteroperca microlepis) space-use correlations with landscape structure and environmental conditions

To explore variation in space use under different environmental conditions, we acoustically tagged gag (Mycteroperca microlepis) established on experimental artificial reefs in the Gulf of Mexico and used an acoustic positioning array to record animal positions during the winters of 2007 and 2008. From side-scan sonar imagery, we created a categorical habitat map of the hard- and sand-bottom habitats surrounding the reef. We recorded water conditions using an Acoustic Doppler Current Profiler. Correlations between gag space use (distance from the reef, distance from the seafloor, and travel speed) and environmental conditions (bottom type, time of day, lunar phase, and water temperature, speed and flow direction) showed gag typically using space near, but not directly at the reef. The 50% and 95% kernel density contours fell within 17 and 39m of the reef, respectively, though gag spent the most time about 10m from the reef. All individuals made occasional excursions beyond their primary space-use areas. Gag spent 86% of the time within 2.5m of the seafloor, with periods of frequent or extended movement up to 9m from the seafloor, usually near the reef. On average, gag moved about 25% farther from the reef during the day; correlations with other environmental conditions were weak or unclear. In all cases, variation in space-use among individuals or of particular individuals over time was greater than the variability explained by changing environmental conditions.

Differences in Space Use by Common Ravens in Relation to Sex, Breeding Status, and Kinship

Abstract. Group differences in avian space use relate to group differences in resource use and demographic parameters. However, studies that consider year-round, intraspecific variation in the space use of noncooperatively breeding species are relatively rare. A greater understanding of factors relating to intraspecific variation in space use is especially important for managing human-subsidized predators, such as the Common Raven (Corvus corax). We hypothesized that sex, sociality, and the distribution of bonanzas of food should influence year-round space use by breeding and nonbreeding Common Ravens on the Olympic Peninsula of Washington State. We detected differences in space use between breeders and nonbreeders but not between the sexes. Breeders shared little space with their neighbors and displayed strong site fidelity, except in the fall and winter or after the death of a mate, when some breeding ravens moved extensively. Nonbreeders moved widely, were more gregarious, and their home ranges interse...

Interannual home range variation, territoriality and overlap in breeding Bonelli’s Eagles (Aquila fasciata) tracked by GPS satellite telemetry

Animal movement patterns and use of space depend upon environmental resources (i.e., food availability), and on conspecific and interspecific interactions. We studied the home range of seven territorial Bonelli’s Eagles (Aquila fasciata) tracked by GPS satellite telemetry over a period of 4–5 years to determine home range characteristics and annual and individual variations. Bonelli’s Eagles hold an annual home range of Minimum Convex Polygon (MCP) = 205.6 km2 (range 44.7–704.8 km2) and Kernel 95 % = 44.4 km2 (range 31.8–91.9 km2). Eagles showed slight temporal variation in home range sizes, but a wide variation in use of space. Only 27.3 % of the accumulated home range was used during all seasons, while 30.3 % was used only during a single season. Areas around the nest, main hunting areas and roosting sites were utilised regularly every year in both breeding and non-breeding seasons. Accumulated home ranges were stabilised in year 3 of monitoring. Individuals displayed strong territoriality, even in non-breeding seasons, although eagles also made long trips (>15 km) well beyond their territorial boundaries, as assessed for the first time by GPS satellite telemetry. The overlap was slight for two adjacent pairs. In addition, we noticed a strong relationship between topographical landmarks and home range segregation. This study reinforces the idea that combining information on season patterns, conspecific distribution and topography can help define both the shape and size of home ranges more realistically.

Effects of spatial scale and sample size in GPS-based species distribution models: are the best models trivial for red deer management?

Species distribution models (SDMs) are popular in conservation and management of a wide array of taxa. Often parameterized with coarse GIS-based environmental maps, they perform well in macro-ecological settings but it is debated if the models can predict distribution within broadly suitable "known" habitats of interest to local managers. We parameterized SDMs with GIS-derived environmental variables and location data from 82 GPS- collared female red deer (Cervus elaphus) from two study areas in Norway. Candidate GLM models were fitted to address the effect of spatial scale (landscape vs. home range), sample size, and transferability between study areas, with respect to predictability (AUC) and explained variance (Generalized R 2 and deviance). The landscape level SDM captured variation in deer distribution well and performed best on all diagnostic measures of model quality, caused mainly by a trivial effect of avoidance of non-habitat (barren mountains). The home range level SDMs were far less predictable and explained comparatively little variation in space use. Landscape scale models stabilized at the low sample size of 5-10 individuals and were highly transfer- rable between study areas implying a low degree of individual variation in habitat selection at this scale. It is important to have realistic expectations of SDMs derived from digital elevation models and coarse habitat maps. They do perform well in highlighting potential habitat on a landscape scale, but often miss nuances necessary to predict more fine-scaled distribution of wildlife populations. Currently, there seems to be a trade-off between model quality and usefulness in local management.

Intraspecific variation in space use, group size, and mating systems of caviomorph rodents

Intraspecific variation in social systems is widely recognized across many taxa, and specific models, including polygamy potential, resource defense, and resource dispersion, have been developed to explain the relationship between ecological variation and social organization. Although mammals from temperate North America and Eurasia have provided many insights into this relationship, rodents from the Neotropics and temperate South America have largely been ignored. In this review we focus on reports documenting intraspecific variation in spacing systems, group size, and mating systems of caviomorphs. This large group of New World hystricognath rodents occupies a diverse array of habitats; thus, members of the same species potentially exhibit different social systems in response to different ecological conditions. Spatial patterns vary in response to a diverse array of factors, including predation, food availability, population density, and soil characteristics. Changes in group size typically correlate with changes in resource availability, particularly food. Mating systems generally reflect the ability of males to control access to females, which may depend on population density or food distribution. In general, social organization in caviomorphs fits predictions of resource-based models; however, most studies have been purely observational, involving small numbers of animals over short time periods and reporting qualitative rather than quantitative levels of ecological correlates. In future studies the use of molecular techniques and controlled, experimental manipulations can increase our understanding of intraspecific variation in caviomorph social systems. This understudied group of rodents offers excellent opportunities to provide insights into the influence of ecological conditions on behavior such as social systems.

Postfledging family space use in great tits in relation to environmental and parental characteristics

Parental care has been widely studied in birds and mammals, but variation in space use in family groups has received less attention, despite its potential importance for both survival and subsequent dispersal of offspring. In this study, we evaluate factors affecting postfledging family space use in a small territorial songbird, the great tit (Parus major). Family space use was monitored using radio tracking. Our main objectives were 1) to quantify in detail the temporal and spatial scale of family movements, 2) to test behavioral hypotheses explaining when and how frequently families leave their breeding territory, and 3) to test to what extent movements were based on familiarity with the environment. We found that variation in space use was to a large extent due to some families, but not others, regularly undertaking foraging excursions of up to more than a kilometer away. Daily excursion probability was higher for families occupying low-quality territories, and consequently, these families covered larger areas during foraging. Excursion behavior and range use also strongly depended on maternal breeding experience and personality. We further present some striking examples of inexperienced mothers moving toward previously visited areas, suggesting that familiarity with the environment plays an important role in patterns of space use. Overall, our results suggest that variation in family movements reflects different foraging strategies in relation to parental characteristics. Copyright 2011, Oxford University Press.

SPACING AS A PREDICTOR OF SOCIAL ORGANIZATION IN KANGAROO RATS (DIPODOMYS HEERMANNI ARENAE)

We examined intraspecific space use of free-ranging kangaroo rats (Dipodomys heermanni) during the breeding season using behavioral observations and radiotelemetry. Home ranges of males were significantly larger than those of females. Female D. heermanni maintained exclusive territories with essentially nonoverlapping home ranges, whereas home ranges of males overlapped with both same- and opposite-sex conspecifics, reflecting the different strategies of the different sexes. This follows a general pattern found in mammals in which spacing reflects limiting resources. There was, however, high individual variation in home range size for males, which may suggest a role for social interactions in determining spatial behavior in this species. D. heermanni, a medium-size species, appears intermediate in space use compared with the larger D. spectabilis and the smaller D. merriami. Spacing systems characterize the pattern of distribution of individuals in a population in space and time. The location of an individual is influenced by presence or absence of other individuals (Brown and Orians 1970), distribution of food resources (Covich 1976; Emlen and Oring 1977), and extent of suitable habitat. The social processes by which resources are allocated among members of the population determine spatial organization. Hence, spatial organization of a population can be used to predict its social organization. Patterns of space use by mammals have been the subject of numerous discussions and empirical tests (Lott 1991). One metric for space use is home range size, which is a compromise between environmental conditions and selective factors such as primary production, individual metabolic requirements, predation, and social pressures. These interacting factors often lead to different levels of social interaction between and within species. For solitary rodents in particular, variation in use of space is related to sex, season, geography, and competitive behavior (Armitage 1999; Ebensperger and Bozinovic 2000;

Space-use strategies of female polar bears in a dynamic sea ice habitat

In environments with high spatiotemporal variability in resources, animals may exhibit nomadic movements for resource tracking as opposed to long-term area fidelity. Polar bears (Ursus maritimus) inhabit the dynamic sea ice, preying on seals, and demonstrate considerable intraspecific variation in space use. We studied patterns of fidelity and annual range size for 74 adult female polar bears captured in the Norwegian Arctic that were tracked for up to 5 years using satellite telemetry data. We used the autocorrelation structure of movements and distance between observations at a 1-year interval as measures of fidelity. The female polar bears had a circannual migration pattern. Annual range size varied with reproductive state and geographic location of the range. Females entering maternity dens had smaller annual ranges than females not entering dens. Nearshore females had smaller annual ranges than pelagic females, demonstrating different space-use strategies. Repeatability of movement patterns indicated strategy specialization. We suggest that the different space-use strategies result from variation in habitat and prey selection and in sea-ice dynamics. Factors affecting population and predator–prey dynamics may interact differently with the different space-use strategies and yield strategy-dependent outcomes, therefore a knowledge of movement strategies may be important for understanding polar bear population dynamics.