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Behavioral Ecology and Sociobiology

, Volume 54, Issue 1, pp 22–29 | Cite as

Forced dispersal of juvenile guanacos (Lama guanicoe): causes, variation, and fates of individuals dispersing at different times

  • Ronald J. SarnoEmail author
  • Michael S. Bank
  • Hal S. Stern
  • William L. Franklin
Original Article

Abstract

We examined adult-juvenile conflict in the guanaco (Lama guanicoe). During spring, territorial males become increasingly aggressive toward all juveniles born the previous year and begin expelling them from family groups. In an apparent effort to reduce aggression, juveniles display submissive crouches when being observed, approached, or attacked by the territorial male. Therefore, we assessed the influence of juvenile submissive behavior on the timing of dispersal and also examined if dispersal time was related to survival and reproductive performance as adults. We also evaluated hypotheses regarding the evolution of juvenile mammalian dispersal in the context of if and how each may favor the forced dispersal of juvenile guanacos by territorial males. Juveniles generally dispersed in late spring and early summer, and a nearly equal proportion of females (n=46; 48%) and males (n=49; 52%) dispersed. More-submissive animals generally dispersed later than less-submissive animals. Juvenile sex and dispersal time were not related to survival. In contrast, juvenile sex and dispersal time were related to reproductive performance. The probability of reproducing was highest when juveniles dispersed early and decreased with increasing time in family groups prior to dispersal. The largest proportion of juveniles was forced to disperse during a 2-week interval following the peak of the breeding season. Competition for food resources is likely very intense at this juncture and territorial males may force older juveniles to disperse in order to divert food resources to younger neonates. Additionally, juveniles may be forced to disperse after territorial males mate their mothers to prevent lost mating opportunities, because females leave territories when their offspring disperse and possibly prior to mating with males. We conclude that the forced dispersal of juvenile guanacos by territorial males is ultimately driven by competition for food resources on territories. The timing of dispersal, however, may be tempered by the chronology of matings between territorial males and particular adult females, and/or genetic relatedness between territorial males and juveniles.

Keywords

Dispersal Lama guanicoe Aggression Survival 

Notes

Acknowledgements

We thank the Chilean National Forestry and Park Service (CONAF) and the administration at Torres del Paine National Park for their assistance and collaboration, particularly G. Santana, J. Toro, and N. Soto. The comments of A. Engh, M. Festa-Bianchet, D. Watts, and two anonymous reviewers greatly improved the manuscript. We thank A. Anderson, C. Bergman, T. Chladny, J. Cleckler, A. Engh, E. Gaylord, K. Gaylord, K. Guderian, P. Heaven, N. Nebbe, K. Nielsen, I. O'Connell, W. Prexl, J. Rathje, J. Reed, S. Shoemaker, C. Solek, B. Soppe, K. Stueckraarth, T. Sulser, and N. Varley for their invaluable assistance in the field. Capture and handling permits were issued by Servicio Agricola y Ganadero (SAG) in Punta Arenas, Chile. This study was supported by Patagonia Research Expeditions, National Science Foundation Grant no. BSR-9112826, and Organization of American States Grant no. 19104.

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Ronald J. Sarno
    • 1
    • 4
    Email author
  • Michael S. Bank
    • 2
  • Hal S. Stern
    • 3
  • William L. Franklin
    • 1
  1. 1.Department of Animal Ecology and Program in Ecology and Evolutionary BiologyIowa State UniversityAmesUSA
  2. 2.Program in Ecology and Environmental Science, Department of Biological SciencesUniversity of MaineOronoUSA
  3. 3.Department of StatisticsUniversity of CaliforniaIrvineUSA
  4. 4.Department of Environmental Science and Program in Interdisciplinary StudiesUniversity of South FloridaTampaUSA

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