title: Density triggers maternal hormones that increase adaptive offspring growth in a wild mammal.
abstract: In fluctuating environments, mothers may enhance the fitness of their offspring by adjusting offspring phenotypes to match the environment they will experience at independence. In free-ranging red squirrels, natural selection on offspring postnatal growth rates varies according to population density, with selection favoring faster-growing offspring under high-density conditions. We show that exposing mothers to high-density cues, accomplished via playbacks of territorial vocalizations, led to increased offspring growth rates in the absence of additional food resources. Experimental elevation of actual and perceived density induced higher maternal glucocorticoid levels, and females with naturally or experimentally increased glucocorticoids produced offspring that grew faster than controls. Therefore, social cues reflecting population density were sufficient to elicit increased offspring growth through an adaptive hormone-mediated maternal effect.
authors.affiliation: Department of Zoology, Michigan State University, East Lansing, MI 48824, USA. bendantzer@gmail.com
authors.forename: Ben
authors.initials: B
authors.lastname: Dantzer
authors.forename: Amy E M
authors.initials: AE
authors.lastname: Newman
authors.forename: Rudy
authors.initials: R
authors.lastname: Boonstra
authors.forename: Rupert
authors.initials: R
authors.lastname: Palme
authors.forename: Stan
authors.initials: S
authors.lastname: Boutin
authors.forename: Murray M
authors.initials: MM
authors.lastname: Humphries
authors.forename: Andrew G
authors.initials: AG
authors.lastname: McAdam
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D003463:Cues; D005260:Female; D005938:Glucocorticoids / Q000378:metabolism*; D048788:Growth and Development; D006854:Hydrocortisone / Q000097:blood; D008098:Litter Size / Q000502:physiology*; D008425:Maternal Behavior / Q000502:physiology*; D011156:Population Density; D012589:Sciuridae / Q000502:physiology*; D012641:Selection, Genetic; D014828:Vocalization, Animal
chemical_list: D005938:Glucocorticoids; D006854:Hydrocortisone