Skip to main content

Parent–offspring and sibling conflict in Galápagos fur seals and sea lions

Abstract

Parent–offspring conflict theory is well supported by theoretical arguments. However, empirical observations are often difficult to interpret and have contradicted one of its most appealing predictions that parent and offspring should disagree over killing of nest or littermates. We present the first examples of deadly conflict between siblings of different cohorts. In Galápagos fur seals (Arctocephalus galapagoensis) and sea lions (Zalophus wollebaeki), mothers often wean their single offspring at 2 years. This leads to a situation where up to 23% of all pups are born while the older sibling is still being nursed. Younger siblings are disadvantaged by being born lighter than neonates without older still dependent siblings. Pups born while an older sib is still dependent grow less in early life (fur seal) and suffer increased early mortality (both species) through direct aggression or scramble competition with the older sibling. This effect is much stronger in years of high sea surface temperature (El Niño) indicating low marine productivity and if the older offspring is a male. In both species, mothers interfere aggressively in this conflict by defending the younger offspring. In years of El Niño, intense resistance to maternal aggression by the older offspring happens frequently in the fur seal. Such resistance against weaning can induce maternal neglect of the newborn. Given substantial year to year variation in offspring growth, maternal aggression forces weaning in the older sibling only if it has reached sufficient size to support itself by foraging. In Galápagos fur seals, pups with older siblings can either represent insurance against loss of older offspring or extra reproductive value.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4

References

  • Altmann J (1974) Observational study of behavior: sampling methods. Behaviour 49:227–267

    PubMed  CAS  Google Scholar 

  • Boyce MS, Haridas CV, Lee CT, and the NCEAS Demography Working Group (2006) Demography in an increasingly variable world. Trends Ecol Evol 21:141–148

    PubMed  Article  Google Scholar 

  • Burnham KP, Anderson DR (1998). Model selection and inference: a practical information-theoretic approach. Springer, New York

    Google Scholar 

  • Cane MA (1983) Oceanographic events during El Niño. Science 222:1189–1195

    PubMed  Article  Google Scholar 

  • Chen D, Cane MA, Kaplan A, Zebiak SE, Huang D (2004) Predictability of El Niño over the last 148 years. Nature 428:733–735

    PubMed  Article  CAS  Google Scholar 

  • Clutton-Brock TH (1991) The evolution of parental care. Princeton University Press, Princeton, NJ

    Google Scholar 

  • Davies NB (1978) Parental meanness and offspring independence: an experiment with hand-reared great tits Parus major. Ibis 120:509–514

    Google Scholar 

  • Dawkins R, Carlisle TR (1976) Parental investment, mate desertion and a fallacy. Nature 262:131–133

    Article  Google Scholar 

  • Dellinger T, Trillmich F (1999) Fish prey of the sympatric Galápagos fur seals and sea lions: seasonal variation and niche separation. Can J Zool 77:1204–1216

    Article  Google Scholar 

  • Drake A, Fraser D, Weary DM (2007) Parent–offspring resource allocation in domestic pigs. Behav Ecol Sociobiol DOI 10.1007/s00265-007-0418-y

  • Fey K, Trillmich F (2007) Sibling competition in guinea pigs (Cavia aperea f. porcellus): scrambling for mother’s teats is stressful. Behav Ecol Sociobiol DOI 10.1007/s00265-007-0419-x

  • Fiedler PC (1994) Seasonal and interannual variability of coastal zone color scanner phytoplankton pigments and winds in the eastern tropical Pacific. J Geophys Res 99:18371–18384

    Article  Google Scholar 

  • Gentry RL (1998) Behavior and ecology of the northern fur seal. Princeton University Press, Princeton, NJ

    Google Scholar 

  • Glynn PW (1988) El Niño-southern oscillation 1982–83: nearshore population, community and ecosystem responses. Ann Rev Ecolog Syst 19:797–813

    Google Scholar 

  • Godfray HCJ (1995) Evolutionary theory of parent–offspring conflict. Nature 376:133–138

    PubMed  Article  CAS  Google Scholar 

  • Guinet C, Georges JY (2000) Growth in pups of the subantarctic fur seal (Arctocephalus tropicalis) on Amsterdam Island. J Zool Lond 251:289–296

    Article  Google Scholar 

  • Hofer H, East ML (2007) Siblicide in Serengeti spotted hyenas: a long-term study of maternal input and cub survival. Behav Ecol Sociobiol DOI 10.1007/s00265-007-0421-3

  • Hoffman JI, Boyd IL, Amos W (2003) Male reproductive strategy and the importance of maternal status in the Antarctic fur seal Arctocephalus gazella. Evolution 57:1917–1930

    PubMed  Google Scholar 

  • Horning M, Trillmich F (1997) Ontogeny of diving behaviour in the Galápagos fur seal. Behaviour 134:1211–1257

    Google Scholar 

  • 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 R Soc Lond B 266:1127–1132

    Article  CAS  Google Scholar 

  • Hudson R, Trillmich F (2007) Sibling competition and cooperation in mammals: challenges, developments and prospects. Behav Ecol Sociobiol DOI 10.1007/s00265-007-0417-z

  • Lamey TC, Evans RM, Hunt JD (1996) Insurance reproductive value and facultative brood reduction. Oikos 77:285–290

    Article  Google Scholar 

  • Lee P, Maljuf P, Gordon IJ (1991) Growth, weaning and maternal investment from a comparative perspective. J Zool Lond 225:99–114

    Article  Google Scholar 

  • Leonard CL, McClain CR (1996) Assessment of interannual variation (1979–1986) in pigment concentrations in the tropical Pacific using the CZCS. Int J Remote Sens 17:721–732

    Article  Google Scholar 

  • Lougheed LW, Anderson DJ (1999) Parent blue-footed boobies suppress siblicidal behavior of offspring. Behav Ecol Sociobiol 45:11–18

    Article  Google Scholar 

  • Maynard-Smith J, Harper D (2003) Animal signals. Oxford University Press, Oxford

    Google Scholar 

  • Mock DW, Forbes LS (1992) Parent–offspring conflict: a case of arrested development. Trends Ecol Evol 7:409–413

    Article  Google Scholar 

  • Mock DW, Forbes S (1995) The evolution of parental optimism. Trends Ecol Evol 7:409–413

    Article  Google Scholar 

  • Mock DW, Parker GA (1986) Advantages and disadvantages of ardeid brood reduction. Evolution 40:459–470

    Article  Google Scholar 

  • Mock DW, Parker GA (1997) The evolution of sibling rivalry. Oxford University Press, Oxford

    Google Scholar 

  • Naidenko SV, Antonevich AL, Erofeeva MN, Neubauer K, Jewgenow K (2004) Sibling aggression in lynx: traits and consequences. Adv Ethol (Suppl) 38:68

    Google Scholar 

  • O’Connor RJ (1978) Brood reduction in birds: selection for infanticide, fratricide and suicide? Anim Behav 26:79–96

    Article  Google Scholar 

  • R Development Core Team (2005) R: a language and environment for statistical computing. Vienna, Austria, R Foundation for Statistical Computing, http://www.r-project.org

  • Trillmich F (1981) Mutual mother-pup recognition in Galápagos fur seals and sea lions: cues used and functional significance. Behaviour 78:21–42

    Google Scholar 

  • Trillmich F (1986a) Maternal investment and sex-allocation in the Galápagos fur seal, Arctocephalus galapagoensis. Behav Ecol Sociobiol 19:157–164

    Google Scholar 

  • Trillmich F (1986b) Attendance behavior of Galápagos fur seals. In: Gentry RL, Kooyman GL (eds) Fur seals. Maternal strategies on land and at sea. Princeton University Press, Princeton NJ, pp 168–185

    Google Scholar 

  • Trillmich F (1986c) Attendance behavior of Galápagos sea lions. In: Gentry RL, Kooyman GL (eds) Fur seals. Maternal strategies on land and at sea. Princeton University Press, Princeton, NJ, pp 196–208

    Google Scholar 

  • Trillmich F (1990) The behavioral ecology of maternal effort in fur seals and sea lions. Behaviour 114:3–20

    Google Scholar 

  • Trillmich F (1996) Parental investment in pinnipeds. Adv Study Behav 25:533–577

    Article  Google Scholar 

  • Trillmich F, Dellinger T (1991) The effects of El Niño on Galápagos pinnipeds. In: Trillmich F, Ono KA (eds) Pinnipeds and El Niño: responses to environmental stress. Springer, Heidelberg, pp 66–74

    Google Scholar 

  • Trillmich F, Kooyman GL (2001) Field metabolic rate of lactating female Galápagos fur seals (Arctocephalus galapagoensis): the influence of offspring age and environment. Comp Biochem Physiol 129A:741–749

    Google Scholar 

  • Trillmich F, Limberger D (1985) Drastic effects of El Niño on Galápagos pinnipeds. Oecologia 67:19–22

    Article  Google Scholar 

  • Trivers RL (1972) Parental investment and sexual selection. In: Campbell B (ed) Sexual selection and the descent of Man. Aldine, Chicago, pp 139–179

    Google Scholar 

  • Trivers RL (1974) Parent–offspring conflict. Am Zool 14:249–264

    Google Scholar 

  • White PA (2007) Maternal response to neonatal sibling conflict in the spotted hyena, Crocuta crocuta. Behav Ecol Sociobiol DOI 10.1007/s00265-007-0422-2

  • Wolf JBW, Kauermann G, Trillmich F (2005) Males in the shade: habitat use and sexual segregation in the Galápagos sea lion (Zalophus californianus wollebaeki). Behav Ecol Sociobiol 59:293–302

    Article  Google Scholar 

Download references

Acknowledgements

This study was supported by the Max-Planck Society, the Deutsche Forschungs-gemeinschaft, the VW-Stiftung and the Friends of the Galápagos, Switzerland. The Galápagos National Park permitted the study of fur seals and sea lions, and the Charles Darwin Station logistically supported the study through its directors Günther Reck, Hendrik Hoeck, Friedemann Köster and Graham Watkins. FT wishes to thank W. Wickler for his steady support and G.L. Kooyman and many field assistants for their wonderful companionship in the field. C. Kraus, J. Krause, D.W. Mock and M. Wikelski gave much appreciated criticism to various drafts of the manuscript. FT wants to thank D.W. Mock for his encouragement to publish the old fur seal data and especially for sharing his many insights and doubts about the state of parent–offspring conflict research during a one month stay in his lab in Norman.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Fritz Trillmich.

Additional information

This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson and Fritz Trillmich).

Communicated by A. Schulte-Hostedde

Appendix

Appendix

Summary of model selection statistics. The number of estimated parameters (K), the residual sum of squares (RSS), Akaike’s information criterion for small sample sizes (AICc), the difference between the minimum AICc of the best candidate model (bold font) and the AICc of the model under consideration (Δ i), Akaike weights (w i) and the Bayesian information criterion (BIC) are given for each model of the candidate set.

Table 4 Influence of presence or absence of older sibling and pup sex on postnatal pup weight in fur seals
Table 5 Influence of presence or absence of older sibling and pup sex on postnatal pup weight in sea lions 
Table 6 Influence of SST anomaly and presence or absence of a sib on pup growth for those pups that survived to 30 days of age 
Table 7 Influence of sea surface temperature anomaly, older sibling’s sex and older sibling’s mass on survival of pups in fur seals

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Trillmich, F., Wolf, J.B.W. Parent–offspring and sibling conflict in Galápagos fur seals and sea lions. Behav Ecol Sociobiol 62, 363–375 (2008). https://doi.org/10.1007/s00265-007-0423-1

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00265-007-0423-1

Keywords

  • Parent–offspring conflict
  • Sibling conflict
  • Siblicide
  • Parental investment
  • Sexual selection
  • Arctocephalus galapagoensis
  • Zalophus wollebaeki