Young flying squirrels (Pteromys volans) dispersing in fragmented forests

Dispersal is a key determinant of the population dynamics ofspecies. Thus, a better understanding of how dispersal is affectedby the landscape structure and how animals make decisions aboutmoving across different landscapes is needed. We studied thedispersal of 60 radio-collared juvenile Siberian flying squirrels(Pteromys volans) in southern Finland. The effect of landscapestructure on selected dispersal direction, dispersal distance,and straightness of dispersal path was studied. Flying squirrelswere capable of dispersing over long distances in fragmentedforest landscapes. The patches used as temporary roosting sitesduring dispersal were of a lower quality than were those usedas finally occupied patches. The patches used were larger thanwere patches on average in the study areas. There was a veryclear directional bias in the dispersal path (i.e., it was nearlya straight line), which remained over a large scale, but wide-openareas obstructed the straightness of the path. As the distancesbetween crossed patches increased, short-distance disperserswere found further away from their natal home range. However,there were no differences in the landscape that could explainthe differences between individuals in decisions to remain philopatricor to become short- or long-distance dispersers. In addition,whereas short-distance dispersers dispersed in random directions,long-distance dispersers started to disperse in directions dominatedby preferred habitat. Thus, there were behavioral differencesbetween dispersers. Our results supported the hypotheses statingthat individuals decide to disperse long or short distancesbefore the onset of dispersal.     

Habitat exploration and use in dispersing juvenile flying squirrels

1. Variation in behaviours involved in habitat selection is important for several evolutionary and ecological processes. For example, habitat use during dispersal may differ from breeding habitat use, and for dispersers the scale of habitat familiarity is determined by exploratory behaviour. We studied habitat use and exploration of 56 radio-collared juvenile flying squirrels Pteromys volans L. within natal home range and during dispersal, and compared habitat use between juveniles and 37 adults within breeding home range. 2. Before dispersal, young flying squirrels actively moved around the natal site. Surprisingly, long-distance dispersers explored less than short-distance dispersers, but philopatric individuals explored similar distances as dispersers. Females explored less than males, although females are the more dispersive sex in flying squirrels. 3. For most of the individuals the settlement area was unfamiliar due to long dispersal distance. Consequently, direction and distance of exploration were not very strong predictors of settlement location. However, individuals familiar with the settlement area concentrated exploration to that area. Exploration did not correlate with short-term survival. 4. Dispersers preferred breeding habitat while dispersing, but were found more often in matrix habitat than juveniles within natal, or adults within breeding, home ranges. 5. We conclude that familiarity does not determine settlement as much as, for example, availability of the habitat for flying squirrels. Based on our results, it also seems clear that data on adult habitat use are not enough to predict habitat use of dispersing individuals. In addition, our results support the recent view that short- and long-distance dispersers may need to be analysed separately in ecological and evolutionary analyses.     

Personality-dependent dispersal cancelled under predation risk

Dispersal is a fundamental life-history trait for many ecological processes. Recent studies suggest that dispersers, in comparison to residents, display various phenotypic specializations increasing their dispersal inclination or success. Among them, dispersers are believed to be consistently more bold, exploratory, asocial or aggressive than residents. These links between behavioural types and dispersal should vary with the cause of dispersal. However, with the exception of one study, personality-dependent dispersal has not been studied in contrasting environments. Here, we used mosquitofish (Gambusia affinis) to test whether personality-dependent dispersal varies with predation risk, a factor that should induce boldness or sociability-dependent dispersal. Corroborating previous studies, we found that dispersing mosquitofish are less social than non-dispersing fish when there was no predation risk. However, personality-dependent dispersal is negated under predation risk, dispersers having similar personality types to residents. Our results suggest that adaptive dispersal decisions could commonly depend on interactions between phenotypes and ecological contexts.     

A comparative analysis of dispersal syndromes in terrestrial and semi‐terrestrial animals

Dispersal, the behaviour ensuring gene flow, tends to covary with a number of morphological, ecological and behavioural traits. While species‐specific dispersal behaviours are the product of each species’ unique evolutionary history, there may be distinct interspecific patterns of covariation between dispersal and other traits (‘dispersal syndromes’) due to their shared evolutionary history or shared environments. Using dispersal, phylogeny and trait data for 15 terrestrial and semi‐terrestrial animal Orders (> 700 species), we tested for the existence and consistency of dispersal syndromes across species. At this taxonomic scale, dispersal increased linearly with body size in omnivores, but decreased above a critical length in herbivores and carnivores. Species life history and ecology significantly influenced patterns of covariation, with higher phylogenetic signal of dispersal in aerial dispersers compared with ground dwellers and stronger evidence for dispersal syndromes in aerial dispersers and ectotherms, compared with ground dwellers and endotherms. Our results highlight the complex role of dispersal in the evolution of species life‐history strategies: good dispersal ability was consistently associated with high fecundity and survival, and in aerial dispersers it was associated with early maturation. We discuss the consequences of these findings for species evolution and range shifts in response to future climate change.     

Habitat choice stabilizes metapopulation dynamics by enabling ecological specialization

Dispersal is a key trait responsible for the spread of individuals and genes among local populations, thereby generating eco‐evolutionary interactions. Especially in heterogeneous metapopulations, a tight coupling between dispersal, population dynamics and the evolution of local adaptation is expected. In this respect, dispersal should counteract ecological specialization by redistributing locally selected phenotypes (i.e. migration load). Habitat choice following an informed dispersal decision, however, can facilitate the evolution of ecological specialization. How such informed decisions influence metapopulation size and variability is yet to be determined. By means of individual‐based modelling, we demonstrate that informed decisions about both departure and settlement decouple the evolution of dispersal and that of generalism, selecting for highly dispersive specialists. Choice at settlement is based on information from the entire dispersal range, and therefore decouples dispersal from ecological specialization more effectively than choice at departure, which is only based on local information. Additionally, habitat choice at departure and settlement reduces local and metapopulation variability because of the maintenance of ecological specialization at all levels of dispersal propensity. Our study illustrates the important role of habitat choice for dynamics of spatially structured populations and thus emphasizes the importance of considering that dispersal is often informed.     

Interacting maternal and spatial cues influence natal – dispersal out of social groups

Proximate cues for animal dispersal are complex and varied. Multiple cues may provide information about different aspects of habitat quality, and these aspects may interact with each other, as well as with population density in different ways. We examined how individuals incorporate multiple cues in their decisions to emigrate and immigrate in the colonial orb‐weaving spider, Cyrtophora citricola. We manipulated maternal feeding as a cue for prey abundance and measured the size of the maternal web, which provides a limited space for philopatric offspring and a second potential dispersal cue. In addition, we recorded all immigration events to determine dispersal distances and the cues juveniles may use in settlement. Dispersal increased when mothers were poorly fed, web sizes were small and clutch sizes were large. In addition to these overall effects, maternal feeding also interacted with web size, indicating that offspring from well‐fed mothers were more tolerant of high sibling densities. We also detected a threshold for the effect of clutch size on dispersal for the first egg sac: below 20 offspring, there was no effect of clutch size, but dispersal increased with clutch size for larger clutches. Dispersal distances were often short, and immigrants preferred sheltered trees and those occupied by adult females. Dispersal not only depended on multiple cues, but these cues interacted, and the importance of web size suggested that saturation of the natal web might force dispersal, at least for spiders with poorly‐fed mothers. How one aspect of habitat quality influences dispersal can therefore depend on the state of other aspects of habitat quality. In particular, some natal resources, such as a nest or territory, may become saturated and limit group size, but this limit will also depend on other factors, such as prey availability.     

Social personalities influence natal dispersal in a lizard

Animal personalities are common across taxa and have important evolutionary and ecological implications. Such consistent individual differences correlate with important life-history traits such as dispersal. Indeed, some environmental conditions are supposed to determine dispersers with a specific personality. For example, an increased density should promote the departure of individuals with less social tolerance. Therefore, we hypothesized that dispersers from high-density populations should primarily be asocial individuals, whereas dispersers from low-density populations should be social individuals. In the common lizard (Lacerta vivipara), we measured attraction towards the odour of conspecifics on juveniles at birth as a metric of social tolerance. We then released these juveniles into populations of different densities and measured dispersal and settlement behaviours with regard to social tolerance. One year later, we again measured the social tolerance of surviving individuals. The social tolerance is constant across time and strongly reflects the individual's dispersal and settlement patterns with respect to population density. These results strongly suggest that social personalities exist and influence dispersal decisions. Further studies will help to elucidate the proximate and ultimate determinants of social personalities.     

Dispersal, interpatch movements, and survival in a shrubland breeding bird community

ABSTRACT Dispersal events can affect the distribution, abundance, population structure, and gene flow of animal populations, but little is known about long‐distance movements due to the difficulty of tracking individuals across space. We documented the natal and breeding dispersal of shrubland birds among 13 study sites in a 1000 km² area in southeastern Ohio. In addition, we radio‐marked and tracked 37 adult males of one shrubland specialist, the Yellow‐breasted Chat (Icteria virens). We banded 1925 juveniles and 2112 adults of nine shrubland species from 2002 to 2005. Of these, 33 (1.7%) juveniles were encountered in subsequent years (2003–2006) as adults (natal dispersal) and 442 (20.9%) birds initially banded as breeding adults were re‐encountered in subsequent years (breeding dispersal). Apparent survival of juvenile shrubland birds on their natal patches was 0.024 (95% CI 0.016–0.036). After accounting for the probability of detection, we found that 21% of birds banded as juveniles and recaptured as adults returned to their natal patches, whereas 78% of adult birds showed fidelity to the patch where they were originally captured. Moreover, natal dispersers tended to move farther than breeding dispersers (corrected natal median = 1.7 km ± 0.37; corrected breeding median = 0.23 km ± 0.10). We used our estimates of natal dispersal and annual apparent survival to estimate true survival at 0.11 (95% CI 0.07–0.18) for juveniles in their first year. However, this estimate was only applicable for birds dispersing within 7 km of their natal patches. Interpatch movements of radio‐marked Yellow‐breasted Chats were not uncommon, with 13 of 37 males located in more than one habitat patch. Overall, we observed low natal philopatry, but high adult site fidelity for shrubland birds in our study area. Considering the frequency of short‐distance movements observed (median = 531 m, range = 88–1045 m), clustering of patches within 1 km might facilitate use of shrubland habitat.     

Dispersal strategies in Tasmanian native hens (Gallinula mortierii)

Individuals in cooperatively breeding species face a complexset of decisions when they reach reproductive maturity. Duringan 8-year study, we examined the histories of 214 Tasmaniannative hens (Gallinula mortierii) from hatching to examinethe strategies they used to acquire breeding positions andthe reproductive success they experienced in those breedingpositions. Two-thirds of young delayed dispersal from theirnatal groups for at least a year. Ecological constraints werea partial cause of delayed dispersal; high-quality territorieswere rare and remained occupied due to high adult survivorship.There were also clear benefits of philopatry. Individuals thatinherited breeding positions on their natal territories gainedbetter quality positions and experienced higher reproductivesuccess in their first breeding attempts than did individualswho dispersed to other groups. Multivariate analyses showedthat the method of acquisition of breeding positions was theonly factor significantly related to the quality of the breedingpositions attained. Males were more likely to inherit breeding positions in their natal groups than were females. The compositionsof individuals' natal groups had no effect on whether theyinherited breeding positions or dispersed. In contrast, thecompositions of groups did appear to affect whether other birdsdispersed into them, with birds rarely moving into groups thatcontained breeders or nonbreeders of the same sex as the potential dispersers. Short-term removals of breeders confirmed this finding.These results suggest that both ecological constraints andbenefits of philopatry explain delayed dispersal in this species.     

The new kid on the block: immigrant males win big whereas females pay fitness cost after dispersal

Dispersal is nearly universal; yet, which sex tends to disperse more and their success thereafter depends on the fitness consequences of dispersal. We asked if lifetime fitness differed between residents and immigrants (successful between‐population dispersers) and their offspring using 29 years of monitoring from North American red squirrels (Tamiasciurus hudsonicus) in Canada. Compared to residents, immigrant females had 23% lower lifetime breeding success (LBS), while immigrant males had 29% higher LBS. Male immigration and female residency were favoured. Offspring born to immigrants had 15–43% lower LBS than offspring born to residents. We conclude that immigration benefitted males, but not females, which appeared to be making the best of a bad lot. Our results are in line with male‐biased dispersal being driven by local mate competition and local resource enhancement, while the intergenerational cost to immigration is a new complication in explaining the drivers of sex‐biased dispersal.     

Effects of conditionally expressed phenotypes and environment on amphibian dispersal in nature

Individuals vary greatly in the distance they disperse, and in doing so, strongly affect ecological and evolutionary processes. Dispersal, when viewed as a component of phenotype, can be affected independently or jointly by environment. However, among taxa with complex life cycles that occupy different habitats over ontogeny, the effects of environment on dispersal and the interaction between environment and phenotype remains poorly understood. Here, we conducted a field experiment to measure how dispersal distance was affected by phenotype, environment experienced before and after metamorphosis, and their interaction. We manipulated the environment encountered by a pond‐breeding salamander Ambystoma annulatum during the aquatic larval stage and again as dispersing terrestrial juveniles. After assaying juvenile phenotype (exploration behavior, body condition, and morphology), we then measured the initial distance dispersed by juveniles. The distance moved by dispersing salamanders was affected by attributes of both larval and juvenile habitat, with salamanders that encountered low quality habitat in either life stage moving the farthest. However, we did not find support for an interactive effect of phenotype and environment affecting the distance moved by dispersers. Interestingly, exploration behavior explained the distance moved by philopatric animals but not dispersing ones. Our findings indicate that the environment experienced before metamorphosis can affect juvenile dispersal behavior, and demonstrates the need to consider dispersal in species with complex life cycles to understand the coupling between local and regional population dynamics.     

Dispersal distances predict subspecies richness in birds

Dispersal ability has been hypothesized to reduce intraspecific differentiation by homogenizing populations. On the other hand, long‐distance dispersers may have better opportunities to colonize novel habitats, which could result in population divergence. Using direct estimates of natal and breeding dispersal distances, we investigated the relationship between dispersal distances and: (i) population differentiation, assessed as subspecies richness; (ii) ecological plasticity, assessed as the number of habitats used for breeding; and (iii) wing size, assessed as wing length. The number of subspecies was negatively correlated with dispersal distances. This was the case also after correcting for potential confounding factors such as migration and similarity due to common ancestry. Dispersal was not a good predictor of ecological plasticity, suggesting that long‐distance dispersers do not have more opportunities to colonize novel habitats. Residual wing length was related to natal dispersal, but only for sedentary species. Overall, these results suggest that dispersal can have a homogenizing effect on populations and that low dispersal ability might promote speciation.     

Sex, isolation and fidelity: unbiased long-distance dispersal in a terrestrial amphibian

Amphibians in general are considered poor dispersers and thus their dispersal curve should be dominated by short movements. Additionally, as male toads do not compete for females and sexual selection is by female choice, dispersal should be male-biased. Furthermore, since adults are site-loyal and polygynous, juveniles should move farther and faster than adults. We tested the hypotheses that dispersal would be limited and both sex- and age-biased in a population of Fowler's toads Bufo fowleri at Lake Erie, Ontario, Canada. Based on a mark-recapture study of 2816 toads, 1326 recaptured at least once, we found that although the toads did show high site fidelity, the dispersal curve was highly skewed with a significant "tail" where the maximum distance moved by an adult was 34 km. Dispersal was neither sex-biased nor age-biased despite clear theoretical predictions that dispersal should be biased towards males and juveniles. We conclude that the resource competition hypothesis of sex-biased dispersal does not predict dispersal tendencies as readily for amphibians as for mammals and birds. Toad dispersal only appears to be juvenile-biased because the juveniles are more abundant than the adults, not because they are the more active dispersers.     

Describing dispersal under habitat constraints: A randomization approach in lesser kestrels

Animal dispersal is usually studied with capture-mark-reencounter data, which provide information on realized dispersal but rarely on underlying processes. In this context, the unreliable assumption of all habitat being available is usually made when describing and analysing dispersal patterns. However, actual settlement options may be constrained by the spatial distribution of appropriate patches, so an important task to understand movement patterns is to adequately describe dispersal when the dispersers’ options are constrained by the sites that are available to them. Using a long-term monitored population of the migratory lesser kestrel, we show how randomization procedures can be used to describe dispersal strategies in such situations. This species breeds colonially in discrete patches, most individuals (83%) disperse from their natal colony, and dispersers tend to move short distances (median=7.2 km). Observed patterns (natal dispersal rates and median dispersal distances of birds emigrating from their natal colony) were compared with those expected from two null models of random settlement of individuals: in any colony available in the whole population, or within the subpopulation (cluster of colonies) of origin. Our simulations indicate that philopatry to the natal colony was much higher than expected under both null expectations, and observed distances were much lower than expected in the whole population. When individuals were constrained to settle within their natal subpopulation in the simulations, dispersal distances were longer than expected in females, but were higher or lower in males depending on year. Dispersal was not only constrained by the spatial distribution of settlement options, but specific hypotheses arise that can be helpful to design and conduct further research. These results challenge previous interpretations of observed dispersal patterns, which may not reflect free decisions of individuals but environmental or social constraints. We suggest using simulation procedures as a routine to advance in the understanding of dispersal ecology and evolution.     

Determining natal dispersal patterns in a population of North American pikas (Ochotona princeps) using direct mark-resight and indirect genetic methods

A combination of direct (mark-resight) and indirect geneticmethods were used to investigate natal dispersal patterns andgenetic population structure in a population of North Americanpikas, Ochotona princeps. Pikas are small lagomorphs found intalus habitat of alpine areas throughout western North America.Adult pikas are individually territorial and rarely disperse.I used multilocus DNA fingerprinting to identify the parentsof juvenile animals. The settlement pattern of marked juvenilesand the pattern of relatedness of pikas across the study sitewas then examined within the study area. Although juvenilesborn at the study site exhibited a philopatric settlement pattern,an isolation-by-distance analysis did not reveal clusters ofhighly related individuals within the population. The F_ST estimatesuggests little genetic differentiation between populations2 km apart, and average DNA fingerprinting band-sharing amongadults was similar to values reported for outbred species. Anaverage of 34% of the adult population was replaced each winterby immigrants. DNA fingerprinting band-sharing analysis suggeststhat these immigrants had dispersed short, intermediate, andlong distances. These findings differ from earlier studies whichused observations of marked animals only to characterize dispersalpatterns. Direct observations of marked juveniles had documenteda philopatric settlement pattern, little or no dispersal outof natal populations, and no direct evidence of long distancemovement. Of the three major hypotheses proposed to explainthe evolution of dispersal in birds and mammals, competitionfor resources, competition for mates, and inbreeding avoidance,the results of this study support a competition for resourceshypothesis, where the key resource is territory     

Personality-dependent dispersal: characterization, ontogeny and consequences for spatially structured populations

Dispersal is one of the most fundamental components of ecology, and affects processes as diverse as population growth, metapopulation dynamics, gene flow and adaptation. Although the act of moving from one habitat to another entails major costs to the disperser, empirical and theoretical studies suggest that these costs can be reduced by having morphological, physiological or behavioural specializations for dispersal. A few recent studies on different systems showed that individuals exhibit personality-dependent dispersal, meaning that dispersal tendency is associated with boldness, sociability or aggressiveness. Indeed, in several species, dispersers not only develop behavioural differences at the onset of dispersal, but display these behavioural characteristics through their life cycle. While personality-dependent dispersal has been demonstrated in only a few species, we believe that it is a widespread phenomenon with important ecological consequences. Here, we review the evidence for behavioural differences between dispersers and residents, to what extent they constitute personalities. We also examine how a link between personality traits and dispersal behaviours can be produced and how personality-dependent dispersal affects the dynamics of metapopulations and biological invasions. Finally, we suggest future research directions for population biologists, behavioural ecologists and conservation biologists such as how the direction and the strength of the relationship between personality traits and dispersal vary with ecological contexts.     

Female-biased natal dispersal in the Siberian flying squirrel

Natal dispersal is usually sex biased in birds and mammals.Female-biased natal dispersal is the prevailing pattern in birdsbut is rare among mammals. Hypotheses explaining sex bias indispersal include the mate-defense mating hypothesis, whichpredicts male-biased dispersal, the resource-defense hypothesispredicting female-biased dispersal, and the competition hypothesis,which predicts that if dispersal is caused by competition forresources between sexes, then the subdominant sex will disperse.We studied natal dispersal of Siberian flying squirrels Pteromysvolans using radio telemetry in Southern Finland in 1996–2004.Of 86 juveniles that survived over the dispersal period, almostall young females dispersed from the natal site, whereas almost40% of males were philopatric. Dispersal was farther for femalesthan males. Females began dispersal on average 2 weeks earlierthan males and were lighter in mass at the onset of dispersalthan later dispersing males. No mate- or resource-defense matingsystem could be found among males, but females seemed to defendnest and apparently food resources, in contrast to the expectationof dispersal bias in resource-defense systems. Competition forresources between sexes does not explain female bias either:in the flying squirrel, the female seems to be the dominantsex. We propose that young females are subordinate to theirmothers and have to disperse to find a vacant, suitable sitefor reproduction.     

Cooperation‐mediated plasticity in dispersal and colonization

Kin selection theory predicts that costly cooperative behaviors evolve most readily when directed toward kin. Dispersal plays a controversial role in the evolution of cooperation: dispersal decreases local population relatedness and thus opposes the evolution of cooperation, but limited dispersal increases kin competition and can negate the benefits of cooperation. Theoretical work has suggested that plasticity of dispersal, where individuals can adjust their dispersal decisions according to the social context, might help resolve this paradox and promote the evolution of cooperation. Here, we experimentally tested the hypothesis that conditional dispersal decisions are mediated by a cooperative strategy: we quantified the density‐dependent dispersal decisions and subsequent colonization efficiency from single cells or groups of cells among six genetic strains of the unicellular Tetrahymena thermophila that differ in their aggregation level (high, medium, and low), a behavior associated with cooperation strategy. We found that the plastic reaction norms of dispersal rate relative to density differed according to aggregation level: highly aggregative genotypes showed negative density‐dependent dispersal, whereas low‐aggregation genotypes showed maximum dispersal rates at intermediate density, and medium‐aggregation genotypes showed density‐independent dispersal with intermediate dispersal rate. Dispersers from highly aggregative genotypes had specialized long‐distance dispersal phenotypes, contrary to low‐aggregation genotypes; medium‐aggregation genotypes showing intermediate dispersal phenotype. Moreover, highly aggregation genotypes showed evidence for beneficial kin‐cooperation during dispersal. Our experimental results should help to resolve the evolutionary conflict between cooperation and dispersal: cooperative individuals are expected to avoid kin‐competition by dispersing long distances, but maintain the benefits of cooperation by dispersing in small groups.     

Influence of Roads,Rivers, and Mountains on Natal Dispersal of White-Tailed Deer

Abstract: Natural and anthropogenic landscape features, such as rivers, mountain ranges, and roads can alter animal dispersal paths and movement patterns. Consequently landscape, through its effects on dispersal, may influence many ecological processes, including disease transmission, invasion dynamics, and gene flow. To investigate influences of landscape features on dispersal patterns of a large mammal, we captured and radiomarked 363 juvenile male white-tailed deer (Odocoileus virginianus), including 212 confirmed dispersers, in 2 topographically dissimilar study areas in Pennsylvania, USA. Dispersal azimuths were uniformly distributed in the western study area (WSA), where there was irregular, hilly topography. Mean dispersal azimuths paralleled ridge direction in the eastern study area, where long parallel ridges were aligned northeast-southwest. Major roads in both areas and a large river in the WSA were semipermeable barriers to dispersal of juvenile males; dispersal paths were less likely to intersect these linear features. Dispersal movements were direct and brief, typically lasting <12 hours. For all dispersers, we found no evidence for preference or avoidance of establishing adult, postdispersal ranges in proximity to roads; however, deer that encountered roads near the terminus of their dispersal path were more likely to stop on the near side. Further, for deer that established postdispersal home ranges near major roads, these features influenced range placement such that locations were typically clustered on one side of the road. The influence of roads, rivers, and mountains on dispersal paths and postdispersal locations of white-tailed deer suggest that landscape-specific features should be considered in conservation and management of this and possibly other species of large mammals.     

Dispersal of Yearling Pronghorns in Western South Dakota

Abstract: We captured and radiocollared 57 pronghorn (Antilocapra americana) fawns in western South Dakota, USA, during May 2002–2003 and radiotracked them through 15 months of age, by which time all surviving individuals had established a permanent home range. We classified 56% (n = 19) of fawns as dispersers and 44% (n = 15) as residents. Eighty-four percent (n = 16) of dispersers departed natal home ranges in late October and occupied winter home ranges for 102–209 days before dispersing to permanent home ranges during April 2003 and 2004. Dispersal distances from natal ranges to permanent home ranges varied from 6.2–267.0 km. Winter home-range sizes for all individual pronghorns varied from 39.4–509.6 km. Permanent home-range size for all individuals varied from 15.5–166.1 km². Mean 95% permanent home-range size differed (P = 0.06) between residents (x̄ = 97.3 ± 15.1 km²) and dispersers (x̄ = 48.6 ± 16.0 km²), but was similar (P = 0.97) among sexes. Mean dispersal distance from natal to permanent home ranges was similar (P = 0.35) for males (x̄ = 54.2 ± 21.0 km) and females (x̄ = 26.3 ± 19.9 km). We suggest that habitat quality (i.e., patchiness) and pronghorn density, in part, stimulated dispersal. We hypothesize that as habitat patch size decreases, home range sizes and distance traveled during predispersal and dispersal movements by pronghorns will increase.