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

• Published in: Oecologia Vol. 181; no. 3; pp. 809 - 817
• Main Authors: Weegman, Mitch D., Bearhop, Stuart, Hilton, Geoff M., Walsh, Alyn J., Weegman, Kaitlin M., Hodgson, David J., Fox, Anthony David
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Science + Business Media 01.07.2016; Springer Berlin Heidelberg; Springer; Springer Nature B.V
• Subjects: Analysis; Animals; Anser albifrons; Anser albifrons flavirostris; Aquatic birds; Arctic region; Biomedical and Life Sciences; Breeding; Cost benefit analysis; Domestic relations; Ecology; Economic aspects; extended families; family relations; Geese; Greenland; herbivores; Hydrology/Water Resources; Life Sciences; Nesting; Offspring; Parents; Plant Sciences; POPULATION ECOLOGY – ORIGINAL RESEARCH; Population theory; probability; progeny; Siblings; Survival; Arctic region; Greenland; Breeding probability; Cost–benefit model; Greenland white-fronted goose; Bayesian multistate model; Long-term family relationship; Fitness
• ISSN: 0029-8549; 1432-1939; 1432-1939
• DOI: 10.1007/s00442-016-3595-4

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.