Behavioral Ecology and Sociobiology

, Volume 59, Issue 1, pp 51–57 | Cite as

Aggression and fighting ability are correlated in the swordtail fish Xiphophorus cortezi: the advantage of being barless

  • Jason A. MoretzEmail author
Original Article


Males of the swordtail fish Xiphophorus cortezi are polymorphic for the pigment pattern vertical bars. Previous studies indicate that barred males exhibit higher levels of aggression towards males with bars than those without, while barless males fail to exhibit differential levels of aggression to either morph. In this study I matched barred and barless males for size and paired them in dyadic contests in order to determine if either morph was more dominant and if so, if dominance was the result of higher aggression levels. I found that barless males had higher bite frequencies and were able to win a majority of the contests while barred males consistently escalated to biting first, even though in most cases they were ultimately the losers. In order to determine whether the observed aggression levels and fighting abilities were inherent to being barless or a consequence of responses to the bars themselves, the dyads were re-paired once after barless males were given temporary bars and once after barred males had their bars removed. Thus, each morph encountered his opponent in both a barred and barless state. Regardless of bar state, naturally barless males continued to be more aggressive and more dominant than their barred counterparts. In addition, naturally barred males only won contests in which they bit more. These results indicate that for this species, aggression is an important component of winning contests when opponents are roughly the same size. As a result, naturally barless males as a whole appear to have higher resource holding potential (RHP) than naturally barred males of the same size because of their greater aggression levels.


Aggression Color morphs RHP Vertical bars Xiphophorus 



I am particularly indebted to Molly Morris for her support and suggestions throughout all phases of this project. I thank Winfried Just, Donald Miles, Willem Roosenburg, and Mathew White for valuable comments on an earlier version of this manuscript. I also thank the Republic of Mexico for permission to collect fish (permit no. DAN02031). This research was supported by NSF grants to J.A. Moretz and M.R. Morris (IBN0309025) and M.R. Morris (IBN9983561), an Ohio University Student Enhancement Award to J.A. Moretz, an Animal Behavior Society Student Research Grant to J.A. Moretz, and by the Department of Biological Sciences at Ohio University. All experiments comply with current laws of the United States and with the Animal Care Guidelines of Ohio University (Animal Care and Use approval L01-01)


  1. Alfredo S, Veiga JP, Martin J, Lopez P, Abelenda M, Marisa P (1996) The cost of producing a sexual signal: testosterone increases the susceptibility of male lizards to ectoparasitic infestation. Behav Ecol 7:145–150CrossRefGoogle Scholar
  2. Archer J (1988) The behavioural biology of aggression. Cambridge University Press, Cambridge, UKGoogle Scholar
  3. Baird TA, Fox SF, McCoy KJ (1997) Population differences in the roles of size and coloration in intra- and intersexual selection in the collared lizard, Crotaphytus collaris: influence of habitat and social organization. Behav Ecol 8:506–517CrossRefGoogle Scholar
  4. Barlow GW (1973) Competition between color morphs of the polychromatic Midas cichlid Cichlasoma citrinellum. Science 179:806–807PubMedCrossRefGoogle Scholar
  5. Barlow GW (1983a) Do gold Midas cichlid fish win fights because of their color, or because they lack normal coloration? Behav Ecol Sociobiol 13:197–204CrossRefGoogle Scholar
  6. Barlow GW (1983b) The benefits of being gold: behavioral consequences of polychromatism in the Midas cichlid Cichlasoma citrinellum. Environ Biol Fishes 8:235–247CrossRefGoogle Scholar
  7. Barlow GW, Siri P (1994). Polychromatic midas cichlids respond to dummy opponents: color, contrast, and context. Behaviour 130:77–112CrossRefGoogle Scholar
  8. Beaugrand J, Goulet C, Payette D (1991) Outcome of dyadic conflict in male green swordtail fish, Xiphophorus helleri: effects of body size and prior dominance. Anim Behav 41:417–424CrossRefGoogle Scholar
  9. Beaugrand J, Payette D, Goulet C (1996). Conflict outcome in male green swordtail fish: interaction of body size, prior dominance/subordination experience, and prior residency. Behavior 133:303–319CrossRefGoogle Scholar
  10. Beeching, SC (1995) Colour pattern and inhibition of aggression in the cichlid fish Astronotus ocellatus. J Fish Biol 47:50–58Google Scholar
  11. Borowsky R (1973) Relative size and the development of fin coloration in Xiphophorus variatus. Physiol Zool 46:22–28Google Scholar
  12. Carpenter GC (1995) Modeling dominance: the influence of size, coloration, and experience on dominance relations in tree lizards. Herp Monogr 9:88–101CrossRefGoogle Scholar
  13. Dugatkin LA, Ohlsen SR (1990) Contrasting asymmetries in value expectation and resource holding power: effect on attack behaviour and dominance in the pumpkinseed sunfish, Lepomis gibbosus. Anim Behav 39:802–804CrossRefGoogle Scholar
  14. Fitzgerald GJ, Kedney GI (1987) Aggression, fighting, and territoriality in sticklebacks: three different phenomena? Biol Behav 12:186–195Google Scholar
  15. Grafen A (1987) The logic of divisively asymmetric contests: respect for ownership and the desperado effect. Anim Behav 35:462–467CrossRefGoogle Scholar
  16. Hammerstein P (1981) The role of asymmetries in animal contests. Anim Behav 19:193–205CrossRefGoogle Scholar
  17. Hintze J (2001). Number Cruncher Statistical Software (NCSS). Kaysville, UTGoogle Scholar
  18. Hoefler CH, Morris MR (1999) A technique for the temporary application and augmentation of pigment pattern in fish. Ethology 195:431–438CrossRefGoogle Scholar
  19. Horth L (2003) Melanic body colour and aggressive mating behaviour are correlated traits in male mosquitofish (Gambusia holbrooki). Proc R Soc Lond B 270:1033–1040CrossRefGoogle Scholar
  20. Hurd PL (1997) Is signaling of fighting ability costlier for weaker individuals? J Theor Biol 184:83–88CrossRefGoogle Scholar
  21. Jakobsson S, Brick O, Kullberg C (1995) Escalated fighting behavior incurs increased predation risks. Anim Behav 49:235–239CrossRefGoogle Scholar
  22. Just W, Morris MR (2003) The Napoleon complex: why smaller males pick fights. Evol Ecol 17:509–522CrossRefGoogle Scholar
  23. Kingston JJ, Rosenthal GG, Ryan MJ (2003) The role of sexual selection in maintaining a color polymorphism in the pygmy swordtail, Xiphophorus pygmaeus. Anim Behav 65:735–743CrossRefGoogle Scholar
  24. Lemel J, Wallin K (1993) Status signaling, motivational condition, and dominance: an experimental study in the great tit, Parus major. Anim Behav 45:549–558CrossRefGoogle Scholar
  25. Mann ME, Ton GC, Wittenberg G, Wittenberg J (2001) Escalated fighting despite predictors of conflict outcome: solving the paradox in a South American cichlid fish. Anim Behav 62:623–634CrossRefGoogle Scholar
  26. Martin RG (1977) Density dependent aggressive advantage in melanistic male mosquitofish (Gambusia holbrooki). Fla Sci 40:393–399Google Scholar
  27. Martin D, Hengstebeck MF (1981) Eye color and aggression in juvenile guppies, Poecilia reticulata. Anim Behav 29:325–331CrossRefGoogle Scholar
  28. Mayar M, Berger A (1992) Territoriality and microhabitat selection in two intertidal New Zealand fish. J Fish Biol 40:243–256CrossRefGoogle Scholar
  29. Maynard Smith J, Parker GA (1976) The logic of asymmetric contests. Anim Behav 24:159–175CrossRefGoogle Scholar
  30. Maynard Smith J, Price GR (1973). The logic of animal conflicts. Nature 46:15–18Google Scholar
  31. Merry JW, Morris MR (2001) Preference for symmetry in swordtail fish. Anim Behav 61:477–479CrossRefGoogle Scholar
  32. Moretz JA (2003) Aggression and RHP in the northern swordtail fish, Xiphophorus cortezi: the relationship between size and contest dynamics in male–male competition. Ethology 109:995–1008CrossRefGoogle Scholar
  33. Moretz JA, Morris MR (2003) Evolutionarily labile responses to a signal of aggressive intent. Proc R Soc Lond B 270:2271–2277CrossRefGoogle Scholar
  34. Morris MR (1998) Female preference for trait symmetry in addition to trait size in swordtail fishes. Proc R Soc Lond B 1399:907–911CrossRefGoogle Scholar
  35. Morris MR, Casey K (1998) Female swordtail fish prefer symmetrical sexual signal. Anim Behav 55:33–39CrossRefPubMedGoogle Scholar
  36. Morris MR, Gass L, Ryan MJ (1995a) Assessment and individual recognition of opponents in swordtails Xiphophorus nigrensis and X. multilineatus. Behav Ecol Sociobiol 37:303–310CrossRefGoogle Scholar
  37. Morris MR, Mussel M, Ryan MJ (1995b) Vertical bars on male Xiphophorus multilineatus: a signal that deters rival males and attracts females. Behav Ecol 6:274–279CrossRefGoogle Scholar
  38. Morris MR, Elias JA, Moretz JA (2001). Defining the sexually selected male trait vertical bars in relation to female preference in the swordtail fish Xiphophorus cortezi. Ethology 107:827–837CrossRefGoogle Scholar
  39. Morris MR, Nicoletto PF, Hesselman E (2003) A polymorphism in female preference for a polymorphic male trait in the swordtail fish Xiphophorus cortezi. Anim Behav 65:45–52CrossRefGoogle Scholar
  40. O'Connor KI, Metcalfe NB, Taylor AC (1999) Does darkening signal submission in territorial contests between juvenile Atlantic salmon, Salmo salar? Anim Behav 58:1269–1276CrossRefPubMedGoogle Scholar
  41. Parker GA (1974) Assessment strategy and the evolution of fighting behaviour. J Theor Biol 47:223–243CrossRefPubMedGoogle Scholar
  42. Pryke SR, Andersson S, Lawes JM, Piper SE (2002) Carotenoid status signaling in captive and wild red-collared widowbirds: independent effects of badge size and color. Behav Ecol 13:622–631CrossRefGoogle Scholar
  43. Raleigh RF, McLearen JB, Groff DG (1973) Effects of topical location branding techniques, and changes in hue on recognition of cold brands in Centrarchid and Salmonoid fish. Trans Am Fish Soc 102:637–641CrossRefGoogle Scholar
  44. Rauchenberger M, Kallman KD, Morizot DC (1990). Monophyly and geography of the Rio Panuco Basin swordtails (genus Xiphophorus) with description of four new species. Am Mus Novit 2975:1–41Google Scholar
  45. Ribowski A, Franck D (1993) Subordinate swordtail males escalate faster than dominants: a failure of the social conditioning process. Aggressive Behav 19:223–229CrossRefGoogle Scholar
  46. Rohwer SA (1975) The social significance of avian winter plumage variability. Evolution 29:593–610CrossRefGoogle Scholar
  47. Rohwer SA (1982) The evolution of of reliable and unreliable badges of fighting ability. Am Zool 22:531–546Google Scholar
  48. Senar JC, Camerino M (1998). Status signaling and the ability to recognize dominants: an experiment with siskins (Carduelis spinus). Proc R Soc Lond B 265:1515–1520CrossRefGoogle Scholar
  49. Zimmerer EJ, Kallman KD (1988) The inheritance of vertical barring (aggression and appeasement signals) in pygmy swordtail Xiphophorus nigrensis (Poeciliidae, Teleostei). Copeia 1988:299–307CrossRefGoogle Scholar
  50. Zucker N, Murray L (1996) Determinants of dominance in the tree lizard Urosaurus ornatus: the relative importance of mass, previous experience, and coloration. Ethology 102:812–825CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of Biological SciencesOhio UniversityAthensUSA
  2. 2.Department of BiologyIndiana UniversityBloomingtonUSA

Personalised recommendations