Androgen-mediated nurturing and aggressive behaviors during paternal care in bluegill sunfish (Lepomis macrochirus) Chandra M.C. Rodgers a, ⁎, Bryan D. Neff a, ⁎, Rosemary Knapp b a Department of Biology, Western University, 1151 Richmond Street N, London, Ontario, Canada N6A 5B7 b Department of Biology, University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA abstract article info Article history: Received 4 June 2012 Revised 14 December 2012 Accepted 16 December 2012 Available online 23 December 2012 Keywords: Bluegill sunfish Lepomis macrochirus Androgens Flutamide Parental care Aggression Nurturing Testosterone 11-Ketotestosterone Trade-off Male parental care in vertebrates often involves both defensive and nurturing behaviors. Whether androgens differentially mediate these two types of behaviors, or a trade-off exists between them, has been studied by behavioral endocrinologists for years but predominantly in species with biparental care. In such systems, potential detrimental effects of elevated androgens on parental care behaviors are often compensated for by changes in behavior of the unmanipulated parent. In contrast, for species where only one parent provides care, manipulation of androgen levels may more clearly determine if there are differential effects of andro- gens on these two types of behaviors and whether the proposed trade-off between defensive and nurturing behavior exists. Here, we manipulated androgen levels in two ways in bluegill sunfish (Lepomis macrochirus), a species where males provide sole parental care for the young. At the onset of the care period, males were implanted with 11-ketotestosterone, a major teleost androgen, the androgen receptor antagonist flutamide, or a blank implant. A separate control group experienced no manipulation. Males were then observed over several days and tested for their aggressiveness towards an experimentally-presented brood predator and for nurturing behavior (fanning of the eggs, removal of dead or fungal-infected eggs). Males implanted with 11-ketotestosterone displayed 64% more aggressive behaviors and 71% fewer nurturing behaviors than control groups. In contrast, males implanted with flutamide displayed 7% fewer aggressive behaviors and 126% more nurturing behaviors than control males. Taken together, these results show that aggression and nurturing behaviors are mediated by androgens and suggest that there is a trade-off between the two behaviors during parental care in this species. © 2012 Elsevier Inc. All rights reserved. Introduction Behavioral endocrinologists have long been interested in the rela- tionship between androgens and aggression. Since 1990, the Chal- lenge Hypothesis proposed by Wingfield et al. (1990) has become a cornerstone for understanding the role that androgens might play in mediating male aggressive behavior in the context of reproduction. The Challenge Hypothesis suggests that high levels of androgens facil- itate territorial aggression or mate defense when confronted with an intruder. To date, the hypothesis has been predominately studied in birds. For example, Hau et al. (2000) found that male spotted antbirds (Hylophylax naevioides) with exogenously elevated androgen levels displayed more aggression in response to a social challenge by anoth- er male than did control males. Conversely, male spotted antbirds implanted with the androgen receptor antagonist-, flutamide-, were less aggressive to a social challenge than were control males. More recently, this phenomenon has been studied in a variety of other taxa including reptiles (e.g., tree lizards, Urosaurus ornatus: Weiss and Moore, 2004), insects (e.g., burying beetles, Nicrophorus: Scott, 2006) and mammals, including humans (e.g., ring-tailed lemurs, Lemur catta: Cavigelli and Pereira, 2000; California mice, Peromyscus californicus: Trainor and Marler, 2001; humans: Archer, 2006; Gettler et al., 2011). Overall, the Challenge Hypothesis has been an important contribution to our understanding of hormone–behavior relationships related to ter- ritorial aggression (see also Hirschenhauser and Oliveira, 2006). As an extension of the Challenge Hypothesis, there has been increasing interest in the potential trade-off between aggression and nurturing behaviors during parental care. It has been proposed that this trade-off is also mediated by androgens. In an early study by Hegner and Wingfield (1987), male house sparrows (Passer domesticus) were implanted with exogenous testosterone (T) or with an androgen recep- tor antagonist. They found that T-implanted males performed more acts of nest defense but fewer acts of nurturing behaviors (i.e. feeding the young) than control males. In contrast, males implanted with the androgen receptor antagonist performed less nest defense but more nurturing behaviors. Likewise, Schwagmeyer et al. (2005) found that T-implanted house sparrows were not only more aggressive towards Hormones and Behavior 63 (2013) 454–461 ⁎ Corresponding authors. Fax: +1 519 661 3935. E-mail addresses: crodger2@alumni.uwo.ca (C.M.C. Rodgers), bneff@uwo.ca (B.D. Neff), rknapp@ou.edu (R. Knapp). 0018-506X/$ – see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.yhbeh.2012.12.008 Contents lists available at SciVerse ScienceDirect Hormones and Behavior journal homepage: www.elsevier.com/locate/yhbeh