In a variety of taxa, individuals behave in consistently different ways. However, there are relatively few studies that empirically test the potential mechanisms underlying the causes and maintenance of these personality differences. Several hypotheses for the causes and maintenance of risky personality traits have been suggested but all have received mixed support. Both the pace-of-life hypothesis and state-dependent safety hypothesis propose that differences in internal state cause and maintain personality traits. Formally, the pace-of-life hypothesis states that differences in life-history traits including productivity (growth) and residual reproductive value (age) create initial differences in individual behaviour that is later maintained by positive feedback, while the state-dependent safety hypothesis suggests that body condition (mass) is responsible for causing and maintaining behavioural differences. We tested and evaluated whether either of these two hypotheses explained the causes or maintenance of variation in risk-related personality traits –defensive aggression, activity and exploration– in yellow-bellied marmots, Marmota flaviventer. We found little support overall for these hypotheses in explaining maintenance in activity or exploration. However, for defensive aggression, we found positive feedback for both mass and age.
Bibliographical noteFunding statement: This work was supported by multiple sources. M.B.P. was supported by a U.S. Department of Education GAANN Fellowship, a National Science Foundation (NSF) GK12 Fellowship and the University of California Los Angeles (UCLA). J.G.A.M. was supported by a Marie-Curie International Incoming Fellowship. D.T.B was supported by the National Geographic Society, UCLA (Faculty Senate and the Division of Life Sciences), a Rocky Mountain Biological Laboratory research fellowship and by the NSF (IDBR-0754247 and DEB-1119660 and 1557130 to D.T.B., as well as DBI 0242960, 0731346 and 1226713 to the Rocky Mountain Biological Laboratory).
Acknowledgments: We thank the many marmoteers who helped us collect trapping data since 2001. We also thank Lynn Fairbanks, Peter Nonacs and two anonymous referees for their helpful comments on previous versions of this manuscript. Research was conducted under UCLA OPRS permit 2001-191.
- pace-of-life hypothesis
- state-dependent safety hypothesis
- yellow-bellied marmot