Risky movements? Natal dispersal does not decrease survival of a large herbivore

Natal dispersal is assumed to be a particularly risky movement behavior as individuals transfer, often long distances, from birth site to site of potential first reproduction. Though, because this behavior persists in populations, it is assumed that dispersal increases the fitness of individuals despite the potential for increased risk of mortality. The extent of dispersal risk, however, has rarely been tested, especially for large mammals. Therefore, we aimed to test the relationship between dispersal and survival for both males and females in a large herbivore. Using a radio-transmittered sample of 398 juvenile male and 277 juvenile female white-tailed deer (Odocoileus virginianus), we compared survival rates of dispersers and non-dispersers. We predicted that dispersing deer would experience greater overall mortality than philopatric deer due to direct transfer-related risks (e.g., vehicular collision), indirect immigration-related mortality attributable to colonization of unfamiliar habitat, and increased over-winter mortality associated with energetic costs of movement and unfamiliarity with recently colonized habitat. For both male and female yearlings, survival rates of dispersers (male = 49.9%, female = 64.0%) did not differ from non-dispersers (male = 51.6%, female = 70.7%). Only two individuals (both female) were killed by vehicular collision during transfer, and over-winter survival patterns were similar between the two groups. Although dispersal movement likely incurs energetic costs on dispersers, these costs do not necessarily translate to decreased survival. In many species, including white-tailed deer, dispersal is likely condition-dependent, such that larger and healthier individuals are more likely to disperse; therefore, costs associated with dispersal are more likely to be borne successfully by those individuals that do disperse. Whether low-risk dispersal of large mammals is the rule or the exception will require additional research. Further, future research is needed to evaluate non-survival fitness-related costs and benefits of dispersal (e.g., increased reproductive opportunities for dispersers).Explanation of data.pdf is a file that explains the format of the input files. Funding provided by: Pennsylvania Game CommissionCrossref Funder Registry ID: http://dx.doi.org/10.13039/100016439Award Number: Funding provided by: Pennsylvania State UniversityCrossref Funder Registry ID: http://dx.doi.org/10.13039/100008321Award Number: Funding provided by: Pennsylvania Audubon Society*Crossref Funder Registry ID: Award Number: Funding provided by: Quality Deer Management Association*Crossref Funder Registry ID: Award Number: Funding provided by: Pennsylvania Deer Association*Crossref Funder Registry ID: Award Number: Funding provided by: Pennsylvania Audubon SocietyCrossref Funder Registry ID: Funding provided by: Quality Deer Management AssociationCrossref Funder Registry ID: Funding provided by: Pennsylvania Deer AssociationCrossref Funder Registry ID:These data were collected on radio-transmittered white tailed deer in Pennsylvania. Data files are input files (.inp) for known-fates analyses in Program MARK. We have also uploaded a .pdf file that further explains the data