Dispersal and habitat cuing of Eurasian red squirrels in fragmented habitats

Abstract

Animal dispersal and subsequent settlement is a key process in the life history of many organisms, when individuals use demographic and environmental cues to target post-dispersal habitats where fitness will be highest. To investigate the hypothesis that environmental disturbance (habitat fragmentation) may alter these cues, we compared dispersal patterns of 60 red squirrels (Sciurus vulgaris) in three study sites that differ in habitat composition and fragmentation. We determined dispersal distances, pre-and post-dispersal habitat types and survival using a combination of capture-mark-recapture, radiotracking and genetic parentage assignment. Most (75%) squirrels emigrated from the natal home range with mean dispersal distance of 1,014 ± 925 m (range 51-4,118 m). There were no sex-related differences in dispersal patterns and no differences in average dispersal distance, and the proportion of dispersers did not differ between sites. In one of the sites, dispersers settled in patches where density was lower than in the natal patch. In the least fragmented site, 90% of animals settled in the natal habitat type (habitat cuing) against 44-54% in the more strongly fragmented sites. Overall, more squirrels settled in the natal habitat type than expected based on habitat availability, but this was mainly due to individuals remaining within the natal wood. In the highly fragmented landscape, habitat cuing among emigrants did not occur more frequently than expected. We concluded that increased habitat fragmentation seemed to reduce reliable cues for habitat choice, but that dispersing squirrels settled in patches with lower densities of same-sex animals than at the natal home range or patch, independent of degree of fragmentation.

No sex bias in natal dispersal of Eurasian red squirrels

“…In our species, bequeathal of the natal home range does not occur . The direct observations of natal dispersal presented in this study confirmed our earlier conclusions (Wauters and Dhondt, 1993;Wauters et al, 1994Wauters et al, , 2010) that dispersal patterns of male and female Eurasian red squirrels are a conditional strategy, best explained by the degree of intra-sexual competition under local conditions.…”

“…Secondly, for 19 juveniles and subadults in SKW, natal patch was determined using maternity assignment in CERVUS 2.0 (Marshall et al, 1998). Details on DNA extraction, and microsatellite loci used for genotyping are given elsewhere (Trizizo et al, 2005;Wauters et al, 2010). Maternity was assigned at 95% and 80% confidence.…”

Responses of small mammals to clear-cutting in temperate and boreal forests of Europe: a meta-analysis and review

“…Moderately intense forest harvest is not considered to be a threat because populations of red squirrels often remain viable in fragmented landscapes (Andrén and Delin 1994;Delin and Andrén 1999;Verbeylen et al 2003). Red squirrels are able to travel relatively long distances on open ground, thus are not as strongly affected by fragmentation as are other arboreal species (Wauters et al 2010;Mortelliti et al 2011). However, the amount of forest cover in the landscape is an important factor related to squirrels' presence (Mortelliti et al 2011) and red squirrels avoid clear-cuts (Hansson 1994).…”

Coupling movement and landscape ecology for animal conservation in production landscapes

“…Memory-based movements involve the use of acquired or 'genetic' information about movement locations. Navigation capacity can be disrupted when habitat quality decreases, habitat becomes fragmented and patches become isolated [41]. The perceptual range is a component of navigation capacity that relates to the distance over which animals can detect suitable areas of habitat (oriented movements).…”

“…[66]), can encourage individuals to remain in patches and reproduce, rather than dispersing into high mortality environments. However, dispersal is important for gene flow and metapopulation persistence, which can be driven by other internal factors, such as avoidance of competition or inbreeding [5,41]. Indeed, selection against dispersal in fragmented landscapes may be maladaptive in the long term if patch recolonization rates are reduced, thus compromising metapopulation viability [60].…”