title: Experimental manipulation of fertility reveals potential lactation costs in a free-ranging marsupial.
abstract: Lactation is the most energetically expensive component of reproduction in mammals. Theory predicts that reproducing females will adjust their behaviour to compensate for increased nutritional demands. However, experimental tests are required, since comparisons of the behaviour of naturally reproducing and non-reproducing females cannot distinguish between true costs of reproduction, individual differences or seasonal variation. We experimentally manipulated reproduction in free-ranging, eastern grey kangaroos (Macropus giganteus), using a fertility control agent. Our novel field experiment revealed that females altered their behaviour in direct response to the energetic demands of reproduction: reproducing females increased bite rates, and thus food intake, when the energetic demands of lactation were highest. Reproducing females did not reduce the time spent on vigilance for predators, but increased their forage intake on faecal-contaminated pasture, thereby increasing the risk of infection by gastrointestinal parasites-a largely unrecognized potential cost of reproduction.
authors: Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia.
authors: Jemma K
authors: JK
authors: Cripps
authors: Michelle E
authors: ME
authors: Wilson
authors: Mark A
authors: MA
authors: Elgar
authors: Graeme
authors: G
authors: Coulson
mesh_terms: D000818:Animals; D004343:Drug Implants / Q000008:administration & dosage; D004734:Energy Metabolism; D005247:Feeding Behavior; D005260:Female; D041981:Gastrointestinal Tract / Q000469:parasitology; D007774:Lactation; D008186:Luteolytic Agents / Q000008:administration & dosage; D007614:Macropodidae / Q000469:parasitology / Q000502:physiology*; D012098:Reproduction; D017329:Triptorelin Pamoate / Q000008:administration & dosage / Q000031:analogs & derivatives; D014739:Victoria
chemical_list: D004343:Drug Implants; D008186:Luteolytic Agents; D017329:Triptorelin Pamoate; C066438:deslorelin