Direct and indirect estimates of dispersal support strong juvenile philopatry and male-biased dispersal in a freshwater turtle species (Emys orbicularis)

Dispersal has major impacts on population dynamics, population genetics
and evolution and is also critical for population management and
conservation. Dispersal is frequently sex- and age-specific, but current
knowledge is strongly taxonomically biased toward birds and mammals. Here,
we provide estimates of dispersal in a threatened freshwater turtle
species, the European pond turtle Emys orbicularis. Based on 15
years of Capture-Mark-Recapture (CMR) monitoring and DNA samples from 194
individuals, we quantified both demographic and genetic dispersal between
three sites separated by 1.5 to 3.5 km. We also investigated the effect of
age and sex on dispersal. Overall, direct (CMR) and indirect (genetic)
approaches provided consistent results showing that the studied sites are
well connected with a flow of about one to three dozen migrants per
generation. Dispersal was both age- and sex-biased in this species, with
frequent dispersal of adult males and a strong philopatry of juveniles (of
both sexes) and adult females. The strong philopatry of juveniles
contrasts with the recurrent higher dispersal rate in young birds and
mammals and shows the relevance of investigating dispersal in various
taxonomic groups. Our results also provide useful information for the
conservation of European pond turtle populations.