Measuring mating competition correctly: available evidence supports operational sex ratio theory

de Jong, Karen; Forsgren, Elisabet; Sandvik, Hanno; Amundsen, Trond
November 2012
Behavioral Ecology;Jan2012, Vol. 23 Issue 6, p1170
Academic Journal
Central to sexual selection theory is the question of when individuals should compete for mates. Theory predicts that the sex ratio of ready-to-mate individuals (operational sex ratio; OSR) affects male and female mating competition. In accordance with this, the strength of mating competition, measured by agonistic behaviors and courtship displays, has been found to co-vary with the OSR in field populations of several species. However, laboratory experiments have often produced results that seemingly contradict OSR theory, especially for courtship behavior. We argue that this may be because experiments typically measure frequencies of competitive behaviors. Frequencies of courtship and agonistic behavior are not only affected by the level of mating competition, but also by the number of potential mates or competitors encountered. In contrast, the propensity to behave competitively at a given encounter represents a behavioral response, and thus directly reflects mating competition. We show in 2 simple models that 1) courtship frequency can be expected to respond differently from courtship propensity to changes in OSR and 2) an increase in frequency of agonistic behaviors could occur even if the propensity is not affected by the OSR. In a meta-analysis of studies on courtship competition, we show that frequency measures produced largely opposite results to propensity measures, as predicted by our model. Moreover, courtship propensity increased when the OSR became more biased toward competitors. This presents strong evidence that the OSR affects competition, in the form of courtship, as predicted by OSR theory.


Related Articles

  • Selection for Social Signalling Drives the Evolution of Chameleon Colour Change. Stuart-Fox, Devi; Moussalli, Adnan // PLoS Biology;Jan2008, Vol. 6 Issue 1, pe25 

    In dwarf chameleons, evolutionary shifts in the capacity for colour change are associated with increasingly conspicuous signals used in contests and courtship rather than by the need to match different backgrounds.

  • Do female zebra finches (Taeniopygia guttata) copy each other's mate preferences? Doucet, Stephanie M.; Yezerinac, Stephen M.; Montgomerie, Robert // Canadian Journal of Zoology;Jan2004, Vol. 82 Issue 1, p1 

    We investigated whether female zebra finches (Tueniopygia guttata) would alter their mate preferences after observing the choices of other females. Experimental trials consisted of four 30-min stages: (A) acclimation, (B) observer female chooses between two males, (C) observer female watches a...

  • How a mouse nose knows it's found a mate. Palmer, D. Jason // New Scientist;8/5/2006, Vol. 191 Issue 2563, p16 

    The article explains the role that scent plays in the mate selection of mice and humans. Scientists have found that mice and humans both have a number of trace amine-associated receptors (TAARs) in their nasal lining. These receptors are thought to pick up on pheromones released by bodily...

  • Insects perceive local sex ratio in the absence of tactile or visual sex-specific cues. Han, Chang; Kang, Chang-Ku; Shin, Hong-Sup; Lee, Jeong-Hyun; Bae, Mi-Rye; Lee, Sang-Im; Jablonski, Piotr // Behavioral Ecology & Sociobiology;Sep2012, Vol. 66 Issue 9, p1285 

    Numerous studies have demonstrated adaptive behavioral responses of males and females to changes in operational sex ratio (the ratio of potentially receptive males to receptive females; OSR), and theory often assumes that animals have perfect instantaneous knowledge about the OSR. However, the...

  • Age at marriage, sex-ratios, and ethnic heterogamy. Stier, Haya; Shavit, Yossi // European Sociological Review;May1994, Vol. 10 Issue 1, p79 

    This paper focuses on the effects of age at marriage and the sex-ratio on patterns of ethnic homogamy among Israeli women. We hypothesize that later marriages are more likely than early marriages to be heterogamous as the 'marriage market' shifts from school to the work-place. By the same token,...

  • Variability of Female Responses to Conspecific vs. Heterospecific Male Mating Calls in Polygynous Deer: An Open Door to Hybridization? Wyman, Megan T.; Charlton, Benjamin D.; Locatelli, Yann; Reby, David // PLoS ONE;2011, Vol. 6 Issue 8, p1 

    Males of all polygynous deer species (Cervinae) give conspicuous calls during the reproductive season. The extreme interspecific diversity that characterizes these vocalizations suggests that they play a strong role in species discrimination. However, interbreeding between several species of...

  • Evidence for seasonal mate limitation in populations of an intertidal amphipod, Corophium volutator (Pallas). Forbes, Mark R.; McCurdy, Dean G.; Lui, Keiko; Mautner, Selma I.; Boates, J. Sherman // Behavioral Ecology & Sociobiology;May2006, Vol. 60 Issue 1, p87 

    Potential rates of reproduction (PRR) differ between the sexes of many animal species. Adult sex ratios together with PRR are expected to determine the operational sex ratio (OSR) defined as the ratio of fertilizable females to sexually active males at any given time. OSR is expected to...

  • Multimodal communication in crayfish: sex recognition during mate search by male Austropotamobius pallipes.  // Canadian Journal of Zoology;Nov2002, Vol. 80 Issue 11, p2041 

    Investigates the role of multiple signals in sex recognition in the crayfish Austropotamobius pallipes. Analysis of the main channels used by males during mate search; Tracking of the behavioral responses of males; Responses of both males and females to chemical and visual stimuli.

  • Lamprey love juice. Scroppo, Dave // Outdoor Life;Feb/Mar2003, Vol. 210 Issue 2, p18 

    Focuses on the experiment conducted by Weiming Li, a Michigan State University professor of biochemistry, wherein he discovered the use of the male sex pheromone to attract ovulating female lampreys.


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics