Female-biased natal and breeding dispersal in an alpine lizard, Niveoscincus microlepidotus

We measured two aspects of dispersal in the alpine Australian scincid lizard, Niveoscincus micolepidotus : (1) natal dispersal, i.e. shift in home range over the lizard's first year of life, and (2) breeding dispersal, i.e. shifts of home ranges between breeding attempts as adults. On average, displacements were surprisingly small. Female neonates dispersed about twice as far as did males in the same cohort (means of 12 m vs. 6 m). A female's natal dispersal distance was not correlated with her body size or our estimate of physiological performance (sprint speed). However, larger, faster-running male neonates dispersed further than did smaller, slower males. As was the case for neonates, adult females moved significantly further between breeding seasons than did adult males (14.2 m vs. 9.6 m). Because of a female's long gestation period (more than 1 year), two groups of females occur simultaneously in the population, non-ovulated (i.e. with yolking folicles) and pregnant females (i.e. approaching parturition). Females that were not yet ovulated showed a markedly stronger dispersal in response to high reproductive effort (i.e. clutch size in relation to body condition) than did pregnant females. In adult males, body size was negatively correlated with dispersal distance, suggesting that although males have overlapping territories, they exhibit an increasing level of site tenacity with age and/or size. Thus, selection for the relatively more pronounced site tenacity in adult males may have resulted in the more marked philopatric behaviour compared to females also as neonates.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 277–283.     

Costs and benefits of female-biased natal philopatry in the common goldeneye

Sex-biased natal dispersal in long-lived species may resultin interactions between parents and mature young of the philopatricsex. To investigate the evolutionary basis of natal philopatryin a noncooperative species, the common goldeneye Bucephalaclangula, we studied possible costs and benefits of simultaneousbreeding of females and philopatric daughters. We did not find any fitness consequences of a daughter's breeding on their mother'sbreeding in terms of nest-site selection, body weight, clutchsize, hatching date, or hatching success. Our results, therefore,did not support the assumption of the local resource competitionhypothesis, that the natally philopatric sex should be morecostly to a breeding parent. As possible benefits for daughters returning to their natal area, we tested inheritance of nestsites from mothers and explored whether daughters utilize thepresence of their mother by parasitically sneaking into hermother's nest. Daughters' nest-site selection was not associatedwith the presence of their mothers. A comparison between daughtersand control females revealed that daughters chose their nestsite closer to their natal nest than expected by nest-siteavailability alone. Daughters could not expect to inherit anest site from their mother, and we did not find other indicationsof cooperation between relatives either. The mother's clutchsize did not increase in the year breeding with the daughter, indicating daughters do not parasitize their mother's nest.We suggest that benefits such as decreased nest predation riskassociated with nesting close to the natal nest site may beimportant in the natal philopatric behavior of the species.     

Dispersal, philopatry, and genetic relatedness in a social carnivore: comparing males and females

A balance must be maintained between the proportion of individuals dispersing and the proportion remaining philopatric such that inbreeding and resource competition are minimized. Yet the relative importance of dispersal and philopatric behaviour is uncertain, especially for species with complex social systems. We examine the influence of dispersal on genetic relationships of a white-nosed coati ( Nasua narica : Procyonidae) population from Panama. Field studies of the coati indicate a social system in which all females are highly philopatric and live in bands while all adult males become solitary at maturity, but do not disperse from the home range of their natal band. Based on analyses of multilocus DNA fingerprints, we confirm that female philopatry is the rule, long-distance dispersal is rare, and that relatedness between most bands is low. However, some new bands result from fission events and these bands retain relatively high relatedness to one another for several years. Adult males inhabiting the home range of a band are closely related to band members. In contrast, males and band members whose ranges do not overlap are unrelated or only slightly related. Adult males are also more closely related to other males whose home ranges they overlap extensively than to males whose home ranges they overlap only slightly. These results indicate that males initially disperse from their natal bands to reduce resource competition and not to avoid inbreeding. Inbreeding avoidance, if it occurs, results from more extensive range movements by males during the mating season.     

Lifetime philopatry in the blue-footed booby: a longitudinal study

Philopatry over the lifetime and its relationship with reproductivesuccess were examined using longitudinal records of nest locationand reproduction of individual blue-footed boobies. Males showedshorter natal dispersal than females, and natal dispersal distanceof both sexes were unrelated to either first reproductive successor lifetime reproductive success. Throughout the early lifetime,males and females nested closer to their first breeding sitesthan to their natal sites, and comparison with a simulationof successive breeding dispersals in random directions showedthat male and female blue-footed boobies are philopatric tothe first breeding site. Therefore, throughout the early lifetime,the first breeding site seems to function as a point of referencefor breeding site use together with the previous season's site.Males and females with shorter natal dispersal distances showedstronger lifetime philopatry to their first breeding sites,suggesting stable individual variation in competitive abilityor dispersal phenotype. However, early lifetime philopatry tofirst breeding sites was unrelated to annual breeding success.Compared with simple fidelity to previous breeding sites, lifetimephilopatry to first breeding sites should result in increasedkin interactions and greater selection for kin recognition,altruism and inbreeding avoidance, as well as long-term familiaritywith neighbors.     

Between-Group Variation in Female Dispersal,Kin Composition of Groups,and Proximity Patterns in a Black-and-White Colobus Monkey (Colobus vellerosus)

A growing body of evidence shows within-population variation in natal dispersal, but the effects of such variation on social relationships and the kin composition of groups remain poorly understood. We investigate the link between dispersal, the kin composition of groups, and proximity patterns in a population of black-and-white colobus (Colobus vellerosus) that shows variation in female dispersal. From 2006 to 2011, we collected behavioral data, demographic data, and fecal samples of 77 males and 92 females residing in eight groups at Boabeng-Fiema, Ghana. A combination of demographic data and a genetic network analysis showed that although philopatry was female-biased, only about half of the females resided in their natal groups. Only one group contained female-female dyads with higher average relatedness than randomly drawn animals of both sexes from the same group. Despite between-group variation in female dispersal and kin composition, female-female dyads in most of the study groups had higher proximity scores than randomly drawn dyads from the same group. We conclude that groups fall along a continuum from female dispersed, not kin-based, and not bonded to female philopatric, kin-based, and bonded. We found only partial support for the predicted link between dispersal, kin composition, and social relationships. In contrast to most mammals where the kin composition of groups is a good predictor of the quality of female-female relationships, this study provides further support for the notion that kinship is not necessary for the development and maintenance of social bonds in some gregarious species.     

Female‐biased dispersal in a bat with a female‐defence mating strategy

The ultimate causes for predominant male‐biased dispersal (MBD) in mammals and female‐biased dispersal (FBD) in birds are still subject to much debate. Studying exceptions to general patterns of dispersal, for example, FBD in mammals, provides a valuable opportunity to test the validity of proposed evolutionary pressures. We used long‐term behavioural and genetic data on individually banded Proboscis bats (Rhynchonycteris naso) to show that this species is one of the rare mammalian exceptions with FBD. Our results suggest that all females disperse from their natal colonies prior to first reproduction and that a substantial proportion of males are philopatric and reproduce in their natal colonies, although male immigration has also been detected. The age of females at first conception falls below the tenure of males, suggesting that females disperse to avoid father–daughter inbreeding. Male philopatry in this species is intriguing because Proboscis bats do not share the usual mammalian correlates (i.e. resource‐defence polygyny and/or kin cooperation) of male philopatry. They have a mating strategy based on female defence, where local mate competition between male kin is supposedly severe and should prevent the evolution of male philopatry. However, in contrast to immigrant males, philopatric males may profit from acquaintance with the natal foraging grounds and may be able to attain dominance easier and/or earlier in life. Our results on Proboscis bats lent additional support to the importance of inbreeding avoidance in shaping sex‐biased dispersal patterns and suggest that resource defence by males or kin cooperation cannot fully explain the evolution of male philopatry in mammals.     

Dispersal,inbreeding avoidance and reproductive success in white-footed mice

The dispersion pattern of 360 juvenile white-footed mice, Peromyscus leucopus, from 158 matings was monitored to determine whether dispersal was sufficient to prevent close inbreeding. Dispersal was male-biased with 20% of the daughters remaining in their natal home ranges. Dispersal of sons was not ‘forced’ by adult males, but may have been influenced by the presence of their mothers. One mother-son and five father-daughter pairs had overlapping home ranges during the breeding season, but the maximum number of matings among close relatives was three of 135 (2·2%). Dispersal of juvenile males was sufficient to keep close inbreeding at a minimum. Dispersal did not result from reproductive competition. Pregnant and post-lactating females frequently moved to new home ranges. The reproductive success of immigrants was the same as that of natal residents.     

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.     

Ecologically determined natal philopatry within a colony of great cormorants

Dispersal patterns of individuals within populations have implicationsfor the social and genetic structure of local populations.Knowing what factors determine individual dispersal behavioris essential for predicting how the population structure willbe influenced by environmental and demographic changes. Inthis study, I investigated whether the settling pattern of individuals breeding for the first time within a colony of greatcormorants was determined by ecological or genetic factors.Furthermore, I examined the possible effects of age and gender.First-time breeders that came back to breed within their natalcolony showed strong philopatry toward their natal breedingsites. Because of the simultaneous strong fidelity of breederstoward their former breeding sites, this caused kin to clusterto some extent around the natal site. However, genetic factors(attraction to close kin) are less likely to explain natalphilopatry than ecological ones (attraction to the natal siteitself). Younger first-time breeders were more philopatric than older ones, in accordance with a decrease in the predictabilityof the quality of breeding sites with increasing time lags.Furthermore, males dispersed farther from the natal breedingsite than females. This result is contrary to what is generallyexpected for a breeding system where the male is dependent on a breeding territory for mate acquisition. I suggest thatthis sex difference could arise because first-time breedingmales are constrained from settling in the natal site by interferencecompetition with older males or because males are better informedabout alternative breeding sites of high quality within thecolony.     

Mother–offspring distances reflect sex differences in fine‐scale genetic structure of eastern grey kangaroos

Natal dispersal affects life history and population biology and causes gene flow. In mammals, dispersal is usually male‐biased so that females tend to be philopatric and surrounded by matrilineal kin, which may lead to preferential associations among female kin. Here we combine genetic analyses and behavioral observations to investigate spatial genetic structure and sex‐biased dispersal patterns in a high‐density population of mammals showing fission–fusion group dynamics. We studied eastern grey kangaroos (Macropus giganteus) over 2 years at Wilsons Promontory National Park, Australia, and found weak fine‐scale genetic structure among adult females in both years but no structure among adult males. Immature male kangaroos moved away from their mothers at 18–25 months of age, while immature females remained near their mothers until older. A higher proportion of male (34%) than female (6%) subadults and young adults were observed to disperse, although median distances of detected dispersals were similar for both sexes. Adult females had overlapping ranges that were far wider than the maximum extent of spatial genetic structure found. Female kangaroos, although weakly philopatric, mostly encounter nonrelatives in fission–fusion groups at high density, and therefore kinship is unlikely to strongly affect sociality.     

Kinship and social structure of bobcats (Lynx rufus) inferred from microsatellite and radio-telemetry data

Kinship analysis using 12 microsatellites was compared with radio-telemetry data to examine the social structure of bobcats Lynx rufus in southern Texas. Genetically identified kinship relationships combined with capture data were used to reconstruct pedigrees. Three family groups were constructed from parent/offspring pairs identified from shared alleles. All parents identified by genetic analysis had established home ranges. Individuals with no distinct home ranges were not genetically observed to have offspring among the bobcats sampled. This suggests that establishing a home range is necessary for bobcats to breed. Of three identified male offspring and three identified female offspring, two female offspring were philopatric. These females became a part of the breeding population in their natal area. Among sibling pairs that included nine female and four male individuals, four females and one male were residents suggesting male-biased dispersal.     

Social and ecological influences on dispersal and philopatry in the plateau pika (Ochotona curzoniae)

Benefits and costs of dispersal and philopatry of the socialplateau pika (Ochotona curzoniae) were studied on the Tibetanplateau for 3 years. Although short-lived, plateau pikas livein cohesive family groups that occupy burrow systems in sedgemeadow habitat Most (57.8%) plateau pikas were philopatric,and dispersal movements were extremely restricted. No juvenilefemales or adult pikas moved more than two family ranges betweenyears; the greatest observed dispersal distances were by twojuvenile males that moved five family ranges from the familyof their birth. Traversing unfamiliar habitat was not a costof pika dispersal because most dispersers settled in familiesthat they could easily visit before dispersal. Dispersal movementsappeared to result in equalization of density among pika families,an expected result if competition for environmental resourcesinfluenced dispersal. Males did not disperse to gain advantagesin competition for mates, as evidenced by their moving to familieswith significantly fewer females. Females, however, moved tofamilies with significantly more males. Males provide abundantpaternal care, and significantly more offspring per female survivedto become adults from families with more adult males per adultfemale. Evidence concerning the influence of inbreeding avoidanceon natal dispersal was indirect. Some males exhibited natalphilopatry; thus some families had opportunity for dose inbreeding.Males and females that dispersed had no opposite-sex relativesin their new families. Philopatric pikas may have benefitedby remaining in families that exhibited low local densities,and philopatric females might have benefited from social cooperationwith relatives.     

The Influence of Kinship on Familiar Natal Migrant Rhesus Macaques (Macaca mulatta)

In most primate species, females remain in the natal group with kin while males disperse away from kin around the time of puberty. Philopatric females bias their social behavior toward familiar maternal and paternal kin in several species, but little is known about kin bias in the dispersing sex. Male dispersal is likely to be costly because males encounter an increased risk of predation and death, which might be reduced by dispersing together with kin and/or familiar males (individuals that were born and grew up in same natal group) or into a group containing kin and/or familiar males. Here we studied the influence of kinship on familiar natal migrant rhesus macaques (Macaca mulatta) on Cayo Santiago, Puerto Rico, by combining demographic, behavioral, and genetic data. Our data suggest that kinship influences spatial proximity between recent natal immigrants and males familiar to them. Immigrants were significantly nearer to more closely related familiar males than to more distantly related individuals. Within a familiar subgroup, natal migrants were significantly closer to maternal kin, followed by paternal kin, then non-kin, and finally to males related via both the maternal and paternal line. Spatial proximity between natal immigrants and familiar males did not decrease over time in the new group, suggesting that there is no decline in associations between these individuals within the first months of immigration. Overall, our results might indicate that kinship is important for the dispersing sex, at least during natal dispersal when kin are still available.     

Families in space: relatedness in the Barents Sea population of polar bears (Ursus maritimus)

The kin structure and dispersal pattern of polar bears ( Ursus maritimus ) of the Barents Sea was investigated during the spring mating season using two complementary approaches. First, individual genotypes based on the analyses of 27 microsatellite loci of 583 polar bears were related to field information gathered from 1146 bears in order to reconstruct the animals' pedigrees and to infer geographical distances between adult bears of different relatedness categories. According to the data, the median natal dispersal distance of the male animals was 52 km while that of the females was 93 km. Second, the relatedness of pairs of adult bears was estimated and correlated to the geographical distance between them. The female dyads had a much stronger kin structure than the male dyads. The 'pedigree approach' revealed a male kin structure which could not be detected using the 'relatedness approach'. This suggests that, on a broader scale, effective dispersal is slightly male biased. Despite fidelity to natal areas, male-mediated gene flow may nevertheless prevent genetic differentiation. Males might occasionally shift their home range which could therefore lead to a male-biased breeding dispersal. Our results showed that a nonterritorial species such as the polar bear that has a high dispersal potential, lives in a highly unstable environment and migrates seasonally is still able to exhibit a distinct kin structure during the mating season.     

Natal dispersal in great bustards: the effect of sex, local population size and spatial isolation

1. We investigated the causes of natal dispersal in four Spanish areas where 35 breeding groups of the polygynous great bustard Otis tarda were monitored intensively. A total of 392 juveniles were radio-tracked between 1991 and 2006 by ground and via aeroplane to avoid potential biases derived from the non-detection of long-distance dispersers. 2. We explored 10 explanatory variables that were related to individual phenotypic features, habitat and conspecific traits in terms of group size and breeding performance, and spatial distribution of available breeding groups. Probability of group change and natal dispersal distances were investigated separately through multifactorial analyses. 3. Natal dispersal occurred in 47.8% of the birds and median natal dispersal distance of dispersers was 18.1 km (range 4.97-178.42 km). Sex largely determined the dispersal probability, with 75.6% of males being dispersers and 80.0% of females being philopatric, in contrast to the general pattern of female-biased dispersal found in most avian species. 4. Both the frequency of natal dispersal and dispersal distances were affected by the spatial distribution of breeding groups. More isolated groups showed a higher proportion of philopatric individuals, the effect being more evident in males than in females. This implies a reduction in gene flow in fragmented populations, as most genetic exchange is achieved through male dispersal. Additionally, dispersers hatched in more isolated groups tended to exhibit longer dispersal distances, which increases the associated energetic costs and mortality risks. 5. The dispersal decision was influenced by the number of conspecifics in the natal group. The individual probability of natal dispersal was related inversely to the size of the natal group, which supports the balanced dispersal model and the conspecific attraction hypothesis. 6. Overall, our results provide a good example of phenotypic plasticity and reinforce the current view that dispersal is an evolutionary complex trait conditioned by the interaction of individual, social and environmental causes that vary between individuals and populations.     

Spring dispersal and agonistic behaviour of the Red-legged partridge (Alectoris rufa)

Spring behaviour, dispersal and population changes were studied in two populations of individually marked Red-legged partridges.
Young males took up home ranges close to their natal site but young females dispersed away. The incidence of agonistic behaviour between males, the extent of the spring decline in population density and the distance dispersed by males between the winter and breeding ranges were less in an area with more abundant nesting cover.
Half the neighbours of a typical male came from the same winter social group. These groups were based on family parties. Males from the same winter group showed less frequent agonistic behaviour to each other and had more overlapped home ranges than those from different groups.     

Sex-biased dispersal in western lowland gorillas (Gorilla gorilla gorilla)

We explored two hypotheses related to potential differences between sexes in dispersal behaviour in western lowland gorillas (Gorilla gorilla gorilla). Direct observations suggest that immature females have more opportunities to move between breeding groups than immature males. The distribution of kin dyadic relationships within and between groups does not, however, support this hypothesis. At larger geographical scales, dispersal is likely to be easier for males than females because of the solitary phase most blackbacks experience before founding their own breeding group. However, previous work indicates that males settle preferentially close to male kin. By specifically tracing female and male lineages with mitochondrial and Y-chromosomal genetic markers, we found that male gorillas in the 6000 km2 area we surveyed form a single population whereas females are restricted to the individual sites we sampled and do not freely move around this area. These differences are more correctly described as differences in dispersal distances, rather than differences in dispersal rates between sexes (both sexes emigrate from their natal group in this species). Differences in resource competition and dispersal costs between female and male gorillas are compatible with the observed pattern, but more work is needed to understand if these ultimate causes are responsible for sex-biased dispersal distances in western lowland gorillas.     

Dispersal as a source of variation in age-specific reproductive strategies in a wild population of lizards

Dispersal syndromes describe the patterns of covariation of morphological, behavioural, and life-history traits associated with dispersal. Studying dispersal syndromes is critical to understanding the demographic and genetic consequences of movements. Among studies describing the association of life-history traits with dispersal, there is anecdotal evidence suggesting that dispersal syndromes can vary with age. Recent theory also suggests that dispersive and philopatric individuals might have different age-specific reproductive efforts. In a wild population of the common lizard (Zootoca vivipara), we investigated whether dispersive and philopatric individuals have different age-specific reproductive effort, survival, offspring body condition, and offspring sex ratio. Consistent with theoretical predictions, we found that young dispersive females have a higher reproductive effort than young philopatric females. Our results also suggest that the early high investment in reproduction of dispersive females trades-off with an earlier onset of senescence than in philopatric females. We further found that young dispersive females produce smaller offspring in lower body condition than do young philopatric females. Overall, our results provide empirical evidence that dispersive and philopatric individuals have different age-specific life-history traits.     

Great bustard population structure in central Spain: concordant results from genetic analysis and dispersal study.

We found significant sex differences in the mtDNA genetic structure and dispersal patterns of great bustards in a population of 11 breeding groups, "leks", in central Spain. The analysis of genetic distances showed that the female population was divided into three groups of leks separated by ca. 50 km, whereas male haplotypes were randomly distributed among leks. Genetic distances among pairs of leks were positively correlated with geographical distances in females but not in males. While female haplotype distributions were homogeneous among leks at close distances, differences in male genetic structure were highly variable even between two close leks. These results from genetic analyses were concordant with those from a radiotracking study on natal dispersal. Natal dispersal distances were higher in males than in females. Also, the frequency of movement of a female between two leks was positively correlated with their genetic affinity and geographical proximity. In males, the frequency of movement was correlated with geographical proximity but not with genetic affinity. Males dispersed among genetically unrelated leks, contributing to keep nuclear genetic diversity in the population, whereas females tended to be philopatric. These results suggest that isolation-by-distance influences the distribution of maternal lineages at a regional level.     

Kin clustering in barnacle geese: familiarity or phenotype matching?

We investigated the settling pattern of barnacle geese Branta leucopsis that returned to breed in their natal colony. Femalesnested close to their parents and sisters, but settling ofmales conformed to a random pattern. The apparent preferencefor breeding close to kin in females could be a by-productof extreme philopatry to the natal nest site. However, sistersalso nested close to each other when settling on a differentisland than the one where their parents bred, pointing at agenuine preference for breeding close to kin. Females onlynested close to sisters born in the same year (i.e., sistersthat they had been in close contact with). This suggests thatthe clustering of female kin in barnacle geese does not resultfrom phenotype matching. We did not detect any direct benefitsof settling close to birth site or kin, but the analyses lackedpower to detect small benefits of proximity to kin given themany other factors that may influence breeding success. Coloniallybreeding birds share characteristics that are generally believedto promote the evolution of cooperation, yet kin clusteringand kin selection have been little studied in this group. Futureresearch should be directed to studying the possible rolesof kin clustering and kin selection in the evolution of coloniality.