Fritz Trillmich Universität Bielefeld, D Title Life history and brood care strategy of guinea pigs: Towards understanding precociality. Abstract An animal's life history provides the key to understanding the way in which fitness is achieved. Studying exceptions has proven a valid way to gain insight into the evolution of life history strategies. For a small 500g mammal, wild cavies follow an unusual life history strategy: After a long pregnancy, they produce small litters with large, highly precocial offspring that mature extremely early. What enables competition of such a life history strategy, which is typical for hystricomorph rodents, with the much more productive strategy normally followed by rodents namely, the production of large litters of highly altricial offspring? Studying two wild species and the domestic guinea pig, we investigated the demography in the wild, the energetics of reproduction, the conditions for maturation, and maternal care behavior in this unusual group and found surprising differences in all these aspects to altricial rodents. The study contributes to our understanding of the competitiveness of this life history in the face of much higher potential rates of reproduction in altricial rodents. Biography Fritz Trillmich studied biology at the University of Freiburg. He did his PhD under the direction of W. Wickler at the Ludwig-Maximilians Universität München in 1976 about "Paarzusammenhalt und Individuelles Erkennen beim Wellensittich" (Pair bonding and individual recognition in budgerigars). During a two-year Postdoc in Galápagos, he studied the behavioral ecology of fur seals, sea lions and marine iguanas. From 1978 to 1990 he was Assistant Researcher at the Max-Planck Institute for Behavioral Physiology in Seewiesen. During this period, he paid many further visits to the Galapagos continuing these studies. In 1982/83 he spent 5 months as a Visiting Scientist at the Scripps Institution, San Diego, USA. Since 1990 he works at the University of Bielefeld where he occupies the chair of Animal Behavior. Present research is centered on life history decisions, mother offspring interactions and the weaning process in guinea pigs. Selected recent publications Horning M, Trillmich F 1999. Lunar cycles in diel prey migrations exert a stronger effect on the diving of juveniles than adult Galápagos fur seals. Proc. Royal Soc. Lond. B 266: 1127-1132 Trillmich F, Kooyman GL 2001. Field metabolic rate of lactating female Galápagos fur seals (Arctocephalus galapagoensis): the influence of offspring age and environment. Comp. Biochemistry and Physiology .129A: 741-749 Laurien-Kehnen C, Trillmich F 2003. Lactation performance of guinea pigs (Cavia porcellus) does not respond to experimental manipulation of pup demands. Behav. Ecol. Sociobiol. 53: 145-152 Laurien-Kehnen C, Trillmich F 2004. Maternal food restriction delays weaning in the guinea pig (Cavia porcellus). Animal Behaviour 68: 303-312 Kraus C, Thomson DL, Künkele J, Trillmich F 2004 in press. Living slow and dying young? Life history strategy and age-specific survival rates in a precocial small mammal. Journal Animal Ecology in press.