Selection for fast and slow exploration affects baseline and stress-induced corticosterone excretion in Great tit nestlings, Parus major Mareike Stöwe a,b, ⁎, Balázs Rosivall c , Pieter J. Drent b , Erich Möstl a a Department of Biomedical Sciences/Biochemistry, University of Veterinary Medicine, Veterinärplatz 1, A-1210 Vienna, Austria b Department of Animal Population Biology, Netherlands Institute of Ecology (NIOO-KNAW), PO Box 40, 6666 ZG Heteren, The Netherlands c Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/c, 1117 Budapest, Hungary abstract article info Article history: Received 9 January 2010 Revised 21 August 2010 Accepted 25 August 2010 Available online 31 August 2010 Keywords: Nestling Stress response Corticosterone Great tit Exploration Coping style Personality Selected lines In nestlings, glucocorticoid (GC) secretion has short-term and long-term f itness consequences. For example, short-time elevations trigger begging activity, whereas chronically elevated GC levels impair body condition, growth and cognitive abilities. Despite a growing body of literature on personality traits, the effects of selection for fast and slow exploration on GC secretion have received little attention. We compared baseline and stress-induced hypothalamic–pituitary–adrenal (HPA) axis activity of hand-reared great tit nestlings of lines selected for fast and slow exploration. Nestling droppings were collected under three conditions: control, test (following handling stress, day 14 after hatching) and the following day. The concentrations of excreted immunoreactive corticosterone metabolites (CM) were determined via an enzyme immunoassay. We also observed nestlings' begging behaviour. CM differed significantly between the lines. Nestlings of the fast line excreted lower CM than slow-line birds. In response to handling stress, nestlings excreted significantly higher concentrations of CM than during the control and on the day after handling. Sex and begging activity were not related to CM levels. Under the control condition, but not after handling, males begged significantly more often than females. In both lines, adults excreted significantly less CM compared to nestlings. Both nestlings and adults of the slow line produced higher baseline CM values than fast-line birds. Fast-line nestlings excreted lower baseline CM than nestlings of a wild population not selected for fast or slow exploration. Slow-line nestlings did not. Our results show that selection on the basis of exploratory behaviour affected HPA axis reactivity. © 2010 Elsevier Inc. All rights reserved. Introduction Individuals differ in suites of correlated behavioural and physio- logical characteristics (“personality”, “behavioural syndrome”, “cop- ing style”) leading to a cross-context consistency in the way they deal with challenges (Verbeek et al., 1996, Gosling and John, 1999, Sih et al., 2004, Kralj-Fiŝer et al., 2007). Behavioural phenotypes are genetically and epigenetically heritable (Dingemanse et al., 2002, Drent et al., 2003, Daisley et al., 2004, van Oers et al., 2004a, Evans et al., 2006). In great tits, Parus major, exploratory behaviour is related to aggressiveness (Verbeek et al., 1996, 1999), risk taking (van Oers et al., 2004b, 2005) and the use of social information (Marchetti and Drent, 2000). Moreover, it affects dispersal (Dingemanse et al., 2003), dominance (Verbeek et al., 1999, Dingemanse and de Goede, 2004), coping with defeat (Carere et al., 2001, 2003), mate choice (Groothuis and Carere, 2005), reproductive success (Both et al., 2005, van Oers et al., 2008) and survival (Dingemanse et al., 2004). These patterns have been observed in wild great tits as well as in great tits selected for fast and slow exploration (Drent et al., 2003). It is probable that selection on the basis of exploratory behaviour could be related to glucocorticoid (GC) secretion patterns but surprisingly little attention has been paid to the hypothalamic–pituitary–adrenal (HPA) axis reactivity of the birds of these selection lines. Carere et al. (2003) observed that only slow male great tits excreted higher concentra- tions of immunoreactive corticosterone metabolites (CM) after a social defeat. In a study assessing the effects of social context on hormonal stress-response patterns, females were subjected to handling stress and returned to their home cages either with or without their mate. Females of both lines significantly increased CM excretion in response to handling. Fast females excreted significantly lower CM when with their mate than when they were alone after the stressful event. Slow females showed a trend towards the same result. In addition, slow females sat close to their mate for significantly longer after the handling stress than under the control condition (mates together, no handling stress, Stöwe et al., 2009). Glucocorticoid secretion during early development has wide- ranging consequences on fitness. In altricial nestlings, short-term GC Hormones and Behavior 58 (2010) 864–871 ⁎ Corresponding author. Department of Biomedical Sciences/Biochemistry, University of Veterinary Medicine, Veterinärplatz 1, A-1210 Vienna, Austria. Fax: +43 125077 4190. E-mail address: m_stoewe@hotmail.com (M. Stöwe). 0018-506X/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.yhbeh.2010.08.011 Contents lists available at ScienceDirect Hormones and Behavior journal homepage: www.elsevier.com/locate/yhbeh