title: Alternative reproductive tactics in female striped mice: Solitary breeders have lower corticosterone levels than communal breeders.
abstract: Alternative reproductive tactics (ARTs), where members of the same sex and population show distinct reproductive phenotypes governed by decision-rules, have been well-documented in males of many species, but are less well understood in females. The relative plasticity hypothesis (RPH) predicts that switches between plastic ARTs are mediated by changes in steroid hormones. This has received much support in males, but little is known about the endocrine control of female ARTs. Here, using a free-living population of African striped mice (Rhabdomys pumilio) over five breeding seasons, we tested whether females following different tactics differed in corticosterone and testosterone levels, as reported for male striped mice using ARTs, and in progesterone and oestrogen, which are important in female reproduction. Female striped mice employ three ARTs: communal breeders give birth in a shared nest and provide alloparental care, returners leave the group temporarily to give birth, and solitary breeders leave to give birth and do not return. We expected communal breeders and returners to have higher corticosterone, owing to the social stress of group-living, and lower testosterone than solitary breeders, which must defend territories alone. Solitary breeders had lower corticosterone than returners and communal breeders, as predicted, but testosterone and progesterone did not differ between ARTs. Oestrogen levels were higher in returners (measured before leaving the group) than in communal and solitary breeders, consistent with a modulatory role. Our study demonstrates hormonal differences between females following (or about to follow) different tactics, and provides the first support for the RPH in females.
authors.affiliation: School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa. Electronic address: davina.hill@sruc.ac.uk.
authors.forename: Davina L
authors.initials: DL
authors.lastname: Hill
authors.affiliation: School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa. Electronic address: neville.pillay@wits.ac.za.
authors.forename: Neville
authors.initials: N
authors.lastname: Pillay
authors.affiliation: School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa; Université de Strasbourg, IPHC-DEPE, 23 rue Becquerel 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France; Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland. Electronic address: carsten.schradin@iphc.cnrs.fr.
authors.forename: Carsten
authors.initials: C
authors.lastname: Schradin
mesh_terms: D000818:Animals; D003345:Corticosterone / Q000378:metabolism*; D005260:Female; D008297:Male; D051189:Murinae / Q000502:physiology*; D009425:Nesting Behavior; D011247:Pregnancy; D011374:Progesterone / Q000378:metabolism; D012098:Reproduction; D012621:Seasons; D012726:Sexual Behavior, Animal / Q000502:physiology*; D012919:Social Behavior; D013686:Telemetry; D013739:Testosterone / Q000378:metabolism
chemical_list: D013739:Testosterone; D011374:Progesterone; D003345:Corticosterone
keywords: Cooperative breeding; Endocrinology; Glucocorticoid; Oestrogen; Plural breeding; Single breeder; Social environment; Social flexibility; Social organisation; Sociality