, Volume 99, Issue 2, pp 95–101 | Cite as

Eunuchs as better fighters?

  • Simona Kralj-Fišer
  • Matjaž Kuntner
Original Paper


Male–male competition for females can significantly affect a male’s reproductive success and hence his fitness. Game theory predicts that an individual should avoid fighting when its future reproductive potential is high, but should fight forcefully when its future reproductive potential is insignificant. When mates are scarce, extreme competition and fatal fighting is expected. We recently showed that Nephilengys malabarensis eunuchs, i.e. sterile spider males that lost their genitals during copulation, become more aggressive during male–male contests. Here, we add crucial comparative data by exploring eunuch fighting behaviour in Nephilengys livida from Madagascar, specifically by testing the ‘better fighter hypotheses’ in a laboratory setting. Similar to N. malabarensis, N. livida copulations resulted in total male castration with the severed palp plugging the female genitals in 70.83% cases, which mostly (63.63%) prevented subsequent copulations. Unexpectedly, however, N. livida eunuchs exhibited lower aggressiveness than virgin males. We interpret these results in the light of different mating biology between the so far studied species known for the eunuch phenomenon, which might reflect differing plug effectiveness due to variation in genital anatomy in N. livida, N. malabarensis and Herennia multipuncta. However, detected differences in aggressive behaviour of N. livida versus N. malabarensis eunuchs might also be explained by the species’ ecology, with lower population densities resulting in a relaxed male–male competition making excessive aggression and mate guarding redundant. This study thus questions the generality of overt aggressiveness in mated males with no reproductive value, and highlights the importance of understanding the natural history of species in the question.


Aggression Cannibalism Emasculation Guarding Plugging Nephilidae Nephilengys livida 



We thank three anonymous reviewers and Jutta Schneider for comments on the manuscript, Matjaž Gregorič for the spider collection and laboratory help; Živa Justinek for help with experiments and lab support; and Ingi Agnarsson, Sahondra Lalao Rahanitriniaina and Honore Rabarison for their help in field. This work was funded by the Slovenian Research Agency (grant J1-2063 to MK) and the National Geographic Society (grant 8655-09 to I. Agnarsson, M. Kuntner and T. Blackledge). SKF was supported by Humboldt fellowship for postdoctoral researchers and Humboldt return fellowship.

Supplementary material

114_2011_873_MOESM1_ESM.docx (26 kb)
ESM Experimental workflow. (DOCX 25 kb)


  1. Bean D, Cook JM (2001) Male mating tactics and lethal combat in the nonpollinating fig wasp Sycoscapter australis. Anim Behav 62:535–542CrossRefGoogle Scholar
  2. Buskirk RE, Frohlich C, Ross KE (1984) The natural selection of sexual cannibalism. Am Nat 123:612–625CrossRefGoogle Scholar
  3. Elias DO, Botero CA, Andrade MCB, Mason AC, Kasumovic MM (2010) High resource valuation fuels “desperado” fighting tactics in female jumping spiders. Behav Ecol 21:868–875CrossRefGoogle Scholar
  4. Davis JA, Brown CR (1999) Costs of coloniality and the effect of colony size on reproductive success in purple martins. Condor 101:737–745CrossRefGoogle Scholar
  5. Enquist M, Leimar O (1987) Evolution of fighting behavior—the effect of variation in resource value. J Theor Biol 127:187–205CrossRefGoogle Scholar
  6. Enquist M, Leimar O (1990) The evolution of fatal fighting. Anim Behav 39:1–9CrossRefGoogle Scholar
  7. Fromhage L, Schneider JM (2005a) Virgin doves and mated hawks: contest behaviour in a spider. Anim Behav 70:1099–1104CrossRefGoogle Scholar
  8. Fromhage L, Schneider JM (2005b) Safer sex with feeding females: sexual conflict in a cannibalistic spider. Behav Ecol 16:377–382CrossRefGoogle Scholar
  9. Fromhage L, Schneider JM (2006) Emasculation to plug up females: the significance of pedipalp damage in Nephila fenestrata. Behav Ecol 17:353–357CrossRefGoogle Scholar
  10. Fromhage L, Elgar MA, Schneider JM (2005) Faithful without care: the evolution of monogyny. Evolution 59:1400–1405PubMedGoogle Scholar
  11. Fromhage L, Houston AI, McNamara JM (2008) A model for the evolutionary maintenance of monogyny in spiders. J Theor Biol 250:524–531PubMedCrossRefGoogle Scholar
  12. Hardling KA (2004) Male brood care without paternity increases mating success. Behav Ecol 15:715–772CrossRefGoogle Scholar
  13. Herberstein ME, Barry KL, Turoczy MA, Wills E, Youssef C, Elgar MA (2005) Post-copulation mate guarding in the sexually cannibalistic St Andrew's Cross spider (Araneae Araneidae). Ethol Ecol Evol 17:17–26CrossRefGoogle Scholar
  14. Huntingford FA, Turner AK (1987) Animal Conflict. Chapman and Hall, LondonCrossRefGoogle Scholar
  15. Innocent TM, Savage J, West SA, Reece SE (2007) Lethal combat and sex ratio evolution in a parasitoid wasp. Behav Ecol 8:709–715CrossRefGoogle Scholar
  16. Innocent TM, West SA, Sanderson JL, Hyrkkanen N, Reece SE (2011) Lethal combat over limited resources: testing the importance of competitors and kin. Behav Ecol 22:923–931CrossRefGoogle Scholar
  17. Jormalainen V (1998) Precopulatory mate guarding in crustaceans: male competitive strategy and intersexual conflict. Q Rev Biol 73:275–304CrossRefGoogle Scholar
  18. Kasumovic MM, Bruce MB, Andrade MCB, Herberstein ME (2008) Spatial and temporal demographic variation drives within-season fluctuations in sexual selection. Evolution 62:2316–2325PubMedCrossRefGoogle Scholar
  19. Kokko H, Rankin DJ (2006) Lonely hearts or sex in the city? Density-dependent effects in mating systems. Phil Trans R Soc B 1466:319–334CrossRefGoogle Scholar
  20. Kralj-Fišer S, Gregorič M, Zhang SC, Li D, Kuntner M (2011a) Eunuchs are better fighters. Anim Behav 81:933–939CrossRefGoogle Scholar
  21. Kralj-Fišer S, Schneider JM, Justinek Ž, Kalin S, Gregorič M, Kuntner M (2011b) Mate quality, not aggressive spillover, explains sexual cannibalism in a size dimorphic spider. Behav Ecol Sociobiol doi: 10.1007/s00265-011-1262-7
  22. Kuntner M (2005) A revision of Herennia (Araneae: Nephilidae: Nephilinae), the Australasian 'coin spiders'. Invertebr Syst 19:391–436CrossRefGoogle Scholar
  23. Kuntner M (2007) A monograph of Nephilengys, the pantropical 'hermit spiders' (Araneae, Nephilidae, Nephilinae). Syst Entomol 32:95–135CrossRefGoogle Scholar
  24. Kuntner M, Coddington JA, Hormiga G (2008) Phylogeny of extant nephilid orb-weaving spiders (Araneae, Nephilidae): testing morphological and ethological homologies. Cladistics 24:147–217CrossRefGoogle Scholar
  25. Kuntner M, Kralj-Fišer S, Schneider JM, Li D (2009a) Mate plugging via genital mutilation in nephilid spiders: an evolutionary hypothesis. J Zool 277:257–266CrossRefGoogle Scholar
  26. Kuntner M, Coddington JA, Schneider JM (2009b) Intersexual arms race? Genital coevolution in nephilid spiders (Araneae, Nephilidae). Evolution 63:1451–1463PubMedCrossRefGoogle Scholar
  27. Kuntner M, Agnarsson I, Gregorič M (2009c) Nephilid spider eunuch phenomenon induced by female or rival male aggressiveness. J Arachnol 37:266–271CrossRefGoogle Scholar
  28. Kuntner M, Agnarsson I (2011) Biogeography and diversification of hermit spiders on Indian Ocean islands (Nephilidae: Nephilengys). Mol Phylogenet Evol 59:477–488PubMedCrossRefGoogle Scholar
  29. Maynard Smith J, Price GR (1973) Logic of animal conflict. Nature 246:15–18CrossRefGoogle Scholar
  30. Maynard Smith J, Parker GA (1976) The logic of asymmetric contests. Anim Behav 24:159–175CrossRefGoogle Scholar
  31. Moore JC, Obbard DJ, Reuter C, West SA, Cook JM (2008) Fighting strategies in two species of fig wasp. Anim Behav 76:315–322CrossRefGoogle Scholar
  32. Murray MG, Gerrard R (1985) Putting the challenge into resource exploitation—a model of contest competition. J Theor Biol 115:367–389CrossRefGoogle Scholar
  33. Parker GA (1970) Sperm competition and its evolutionary consequences in insects. Biol Rev Camb Philos Soc 45:525CrossRefGoogle Scholar
  34. Poesel A, Kunc HP, Foerster K, Johnsen A, Kempenaers B (2006) Early birds are sexy: male age, dawn song and extrapair paternity in blue tits, Cyanistes (formerly Parus) caeruleus. Anim Behav 72:531–538CrossRefGoogle Scholar
  35. Reece SE, Innocent TM, West SA (2007) Lethal male–male combat in the parasitoid Melittobia acasta: are size and competitive environment important? Anim Behav 74:1163–1169CrossRefGoogle Scholar
  36. Reinhold K (2003) Influence of male relatedness on lethal combat in fig wasps: a theoretical analysis. Proc R Soc Lond Ser B Biol Sci 270:1171–1175CrossRefGoogle Scholar
  37. Schneider JM, Lubin Y (1998) Intersexual conflict in spider. Oikos 83:496–506CrossRefGoogle Scholar
  38. Stoltz JA, Elias DO, Andrade MCB (2008) Females reward courtship by competing males in a cannibalistic spider. Behav Ecol 62:689–697CrossRefGoogle Scholar
  39. Uhl G, Nessler S, Schneider J (2010) Securing paternity in spiders? A review on occurrence and effects of mating plugs and male genital mutilation. Genetica 138:75–104PubMedCrossRefGoogle Scholar
  40. West SA, Murray MG, Machado CA, Griffin AS, Herre EA (2001) Testing Hamilton’s rule with competition between relatives. Nature 409:510–513PubMedCrossRefGoogle Scholar
  41. West SA, Pen I, Griffin AS (2002) Conflict and cooperation—cooperation and competition between relatives. Science 296:72–75PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Institute of Biology, Scientific Research CentreSlovenian Academy of Sciences and ArtsLjubljanaSlovenia
  2. 2.Biozentrum GrindelUniversity of HamburgHamburgGermany
  3. 3.National Museum of Natural HistorySmithsonian InstitutionWashingtonUSA
  4. 4.College of Life SciencesHubei UniversityWuhanChina

Personalised recommendations