Despite Catch-Up, Prolonged Growth Has Detrimental Fitness Consequences in a Long-Lived Vertebrate
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact firstname.lastname@example.org. . abstract: Individuals experiencing poor growth early in life may later make up their size deficit. Compensatory growth or growth prolongation may lead to such
... on may lead to such catch-up, involving different lifehistory trade-offs under natural conditions. Frequent recaptures and detailed monitoring of animals surviving to asymptotic size are required to compare growth tactics and their fitness consequences. No study to date has obtained such detailed information for wild animals. We used repeated mass measurements (mean 11.6/animal) spanning the lifetime of 104 bighorn ewes (Ovis canadensis) to quantify growth tactics and identify the determinants and life-history costs of these tactics. Growth prolongation, not compensatory growth, led to partial catch-up: mass difference at age 7 was reduced to 4%, for two groups that differed by nearly 20% as yearlings. Ewes that had been light as yearlings prolonged their growth regardless of density or age of primiparity. Growth prolongation did not affect fecundity or longevity. Ewes that experienced poor early growth prolonged growth at the expense of reproductive fitness, weaning a smaller proportion of their lambs. By tracking multiyear growth patterns and comparing events at different life-history stages, we quantified a trade-off between growth and reproduction that would be overlooked if only the adult phenotype was considered. Compensatory growth in long-lived animals appears unlikely when early growth restrictions are mostly density dependent.