title: Individual heterogeneity and offspring sex affect the growth-reproduction trade-off in a mammal with indeterminate growth.
abstract: Reproduction can lead to a trade-off with growth, particularly when individuals reproduce before completing body growth. Kangaroos have indeterminate growth and may always face this trade-off. We combined an experimental manipulation of reproductive effort and multi-year monitoring of a large sample size of marked individuals in two populations of eastern grey kangaroos to test the predictions (1) that reproduction decreases skeletal growth and mass gain and (2) that mass loss leads to reproductive failure. We also tested if sex-allocation strategies influenced these trade-offs. Experimental reproductive suppression revealed negative effects of reproduction on mass gain and leg growth from 1 year to the next. Unmanipulated females, however, showed a positive correlation between number of days lactating and leg growth over periods of 2 years and longer, suggesting that over the long term, reproductive costs were masked by individual heterogeneity in resource acquisition. Mass gain was necessary for reproductive success the subsequent year. Although mothers of daughters generally lost more mass than females nursing sons, mothers in poor condition experienced greater mass gain and arm growth if they had daughters than if they had sons. The strong links between individual mass changes and reproduction suggest that reproductive tactics are strongly resource-dependent.
authors.affiliation: Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, J1K2R1, Canada. gelinuriel@gmail.com.|Laboratoire de Physiologie de la Reproduction et des Comportements, CNRS-UMR 7247-Université de Tours, 37380, Nouzilly, France. gelinuriel@gmail.com.
authors.forename: Uriel
authors.initials: U
authors.lastname: Gélin
authors.affiliation: School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors.forename: Michelle E
authors.initials: ME
authors.lastname: Wilson
authors.affiliation: School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors.forename: Jemma
authors.initials: J
authors.lastname: Cripps
authors.affiliation: School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors.forename: Graeme
authors.initials: G
authors.lastname: Coulson
authors.affiliation: Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, J1K2R1, Canada.|School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors.forename: Marco
authors.initials: M
authors.lastname: Festa-Bianchet
mesh_terms: D000818:Animals; D002149:Energy Intake; D004777:Environment; D005260:Female; D006128:Growth; D006801:Humans; D007774:Lactation; D007866:Leg / Q000254:growth & development; D007614:Macropodidae / Q000502:physiology*; D008297:Male; D009035:Mothers; D012098:Reproduction; D012737:Sex Factors; D012863:Skeleton / Q000254:growth & development; D015430:Weight Gain; D015431:Weight Loss
keywords: Environmental effects; Macropus giganteus; Manipulation; Reproductive costs; Sex allocation