title: Should I stay or should I go? Fitness costs and benefits of prolonged parent-offspring and sibling-sibling associations in an Arctic-nesting goose population.
abstract: Theory predicts persistence of long-term family relationships in vertebrates will occur until perceived fitness costs exceed benefits to either parents or offspring. We examined whether increased breeding probability and survival were associated with prolonged parent-offspring and sibling-sibling relationships in a long-lived Arctic migrant herbivore, the Greenland white-fronted goose (Anser albifrons flavirostris). Although offspring associated with parents for 1-13 years, 79 % of these associations lasted two or less years. Only 65 (9.9 %) of the 656 marked offspring bred once in their lifetime, and just 16 (2.4 %) bred twice or more. The probability of birds with siblings breeding successfully in a subsequent year was credibly greater than that of independent birds at ages 5, 6, and 7. Survival of offspring with parents was credibly greater than that of independent/nonbreeder birds at all possible ages (i.e., ages 2-7+). A cost-benefit matrix model utilizing breeding and survival probabilities showed that staying with family groups was favored over leaving until age 3, after which there were no credible differences between staying and leaving strategies until the oldest ages, when leaving family groups was favored. Thus, most birds in this study either departed family groups early (e.g., at age 2, when the "stay" strategy was favored) or as predicted by our cost-benefit model (i.e., at age 3). Although extended family associations are a feature of this population, we contend that the survival benefits are not sufficient enough to yield clear fitness benefits, and associations only persist because parents and offspring mutually benefit from their persistence.
authors.affiliation: Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Cornwall Campus, Penryn, TR10 9EZ, UK. weegm009@umn.edu.|Wildfowl & Wetlands Trust, Slimbridge, Gloucester, GL2 7BT, UK. weegm009@umn.edu.
authors.forename: Mitch D
authors.initials: MD
authors.lastname: Weegman
authors.affiliation: Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Cornwall Campus, Penryn, TR10 9EZ, UK.
authors.forename: Stuart
authors.initials: S
authors.lastname: Bearhop
authors.affiliation: Wildfowl & Wetlands Trust, Slimbridge, Gloucester, GL2 7BT, UK.
authors.forename: Geoff M
authors.initials: GM
authors.lastname: Hilton
authors.affiliation: National Parks and Wildlife Service, Wexford Wildfowl Reserve, North Slob, Wexford, Ireland.
authors.forename: Alyn J
authors.initials: AJ
authors.lastname: Walsh
authors.affiliation: Department of Biosciences, University of Exeter, Streatham Campus, Exeter, EX4 4QD, UK.
authors.forename: Kaitlin M
authors.initials: KM
authors.lastname: Weegman
authors.affiliation: Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Cornwall Campus, Penryn, TR10 9EZ, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Hodgson
authors.affiliation: Department of Bioscience, Aarhus University, Kalø, Grenåvej 14, 8410, Rønde, Denmark.
authors.forename: Anthony David
authors.initials: AD
authors.lastname: Fox
mesh_terms: D000818:Animals; D001947:Breeding; D003362:Cost-Benefit Analysis; D005777:Geese; D010290:Parents; D035781:Siblings
keywords: Bayesian multistate model; Breeding probability; Cost–benefit model; Fitness; Greenland white-fronted goose; Long-term family relationship