Behav Ecol Sociobiol (2004) 55:561–568 DOI 10.1007/s00265-003-0751-8 ORIGINAL ARTICLE Ashley J. W. Ward · Philip Thomas · Paul J. B. Hart · Jens Krause Correlates of boldness in three-spined sticklebacks (Gasterosteus aculeatus) Received: 6 May 2003 / Revised: 15 December 2003 / Accepted: 18 December 2003 / Published online: 22 January 2004  Springer-Verlag 2004 Abstract Behavioural variation is known to occur be- tween individuals of the same population competing for resources. Individuals also vary with respect to their boldness or shyness. An individual’s position along the shy-bold axis may be defined as the extent to which it is willing to trade off potentially increased predation risks for possible gains in resources. Similarly, group living may be interpreted as a trade-off between anti-predatory tactics and foraging efficiency. The responses of three- spined sticklebacks (Gasterosteus aculeatus) were tested across four social contexts to assess relative boldness or shyness and to further examine whether their behaviour would be consistent within and between contexts. Indi- viduals displayed consistent responses within and be- tween the first two contexts: those individuals which resumed foraging rapidly after a simulated aerial predator attack also displayed low shoaling tendencies. Such fish were deemed to be bold, whilst those which displayed the converse behaviour, slow resumption of foraging and a high shoaling tendency, were deemed to be shy. In a third context, bold individuals out-competed shy conspecifics for food. Boldness was also positively correlated with growth over a 6-week period. The position adopted by an individual within a group is usually interpreted as a trade- off between predation risk and foraging efficiency—both are greater at the front of a mobile group. Bold individuals showed significantly stronger tendencies towards front positions than shy conspecifics. The results suggest that, contrary to some previous studies on other animals, bold or shy behaviour in sticklebacks is consistent between contexts. Keywords Gasterosteus aculeatus · Bold · Shy · Shoaling · Competition Introduction Behavioural variation is known to occur both within and between populations. Populations of Trinidadian guppies (Poecilia reticulata) that are sympatric with the pike cichlid (Crenicichla frenata)—the main predator of guppies—exhibit broadly different behaviour patterns from pike cichlid allopatric populations (Seghers 1974). Within population variation in behaviour patterns is also known to occur, for example in competition for mates (Taborsky 2001) or food (Robinson and Wilson 1994). The shy-bold axis is one such behavioural range across which individuals may vary. The shy-bold range has been identified in a diversity of vertebrate and invertebrate groups, including mammals (Reale et al. 2000; Marchant- Forde 2002), birds (Barnard 1984), fish (Coleman et al. 1998), and crustaceans (Rochette et al. 2001). Boldness may be broadly defined as the willingness to accept a degree of risk in return for potentially higher foraging or reproductive gains. Bolder individuals may therefore show risk-prone behaviour, such as predator inspection, when confronted with a predation threat (Godin and Clark 1997), be prepared to consume novel food sources or interact with new objects (Wilson 1998) or show a greater disposition to explore (Budaev 1997). In contrast to this, individuals at the shy end of the range adopt a risk-averse approach, accepting lower rewards in return for reduced risk. In domesticated animals, where considerable research into the bold-shy range has been done, boldness may be defined as a fearless response to unfamiliar humans (Jezierski and Konecka 1996; Marchant-Forde 2002), which may be interpreted as a variation on the predation risk theme. Communicated by T. Czeschlik A. J. W. Ward ( ) ) · P. J. B. Hart Department of Biology, University of Leicester, Leicester, LE1 7RH, UK e-mail: ajww2@le.ac.uk P. Thomas · J. Krause School of Biology, University of Leeds, Leeds, LS2 9JT, UK