Life history and behavioral type in the highly social cichlid Neolamprologus pulcher

Behavioral Ecology doi:10.1093/beheco/arq024 Advance Access publication 17 March 2010 Life history and behavioral type in the highly social cichlid Neolamprologus pulcher Roger Schürcha,b and Dik Hega Department of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Wohlenstrasse 50A, CH-3032 Hinterkappelen, Switzerland and bDepartment of Evolution, Ecology, and Organismal Biology, The Ohio State University, 318 West 12th Avenue, Columbus, OH 43210-1293, USA a n recent years, findings in noncooperatively breeding species have suggested the use of a new approach to study the interplay between behavioral traits and life-history decisions. Among many taxa, consistent individual variation has been found in explorative behavior (Verbeek et al. 1994; Fraser et al. 2001; Dingemanse et al. 2002; van Oers et al. 2005), boldness (Wilson et al. 1993; Verbeek et al. 1996; Sinn and Moltschaniwskyj 2005), aggressiveness (Bakker 1986; Verbeek et al. 1996; Sinn and Moltschaniwskyj 2005), and risk taking (van Oers, Drent, de Goede, et al. 2004) over time and across contexts. Additionally, these behaviors are often correlated to each other, resulting in behavioral syndromes or animal personalities (Sih, Bell, Johnson 2004; Sih, Bell, Johnson, et al. 2004). The relative inflexibility of these correlated suites of behaviors may generate trade-offs: For example, Sih et al. (2003) have found that salamander larvae could adjust their behavior toward predatory cues only to some degree, leading to a trade-off between growth and predation rate. Theoretical work indicates that different life-history decisions may coselect for different behavioral types, leading to behavioral syndromes: Individuals that focus on future reproductive output should be consistently more risk-averse compared with individuals, which emphasize current reproduction (Wolf et al. 2007). Similarly, Stamps (2007) suggests that correlations between behavioral traits will depend on the effects of the traits on growth and mortality. Subordinates in group-living animals face such trade-offs (e.g., Cahan et al. 2002): They can derive benefits I Address correspondence to R. Schürch. E-mail: schuerch.1@osu .edu. Received 16 April 2009; revised 20 January 2010; accepted 3 February 2010.
The Author 2010. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved. For permissions, please e-mail: from investing in their current group (e.g., subordinate reproductive participation, kin selection, inheritance of the dominant position) or they can derive benefits from investing in obtaining immediately an own dominant breeding position somewhere else (e.g., dominant reproduction after successful dispersal). On top of this, intrinsic differences in the potential to breed as a dominant individual could also lead to distinct behavioral types (West-Eberhard 1975; see also Johnstone 2008), where it pays subordinates with bad breeding prospects to provide help to others, even if relatedness is relatively small. After this reasoning, we here address 2 intriguing core issues in behavioral syndrome research. First, is an individual’s behavioral type fixed throughout life or is it rather affected by his or her state (sensu Houston and McNamara 1999)? Second, what are the social consequences of individuality? If behavioral types are not fixed throughout life, but every individual follows roughly the same developmental trajectory, distinct behavioral types might appear due to comparing individuals from different life stages. Thus, in fact, each individual might actually show the same behavioral type if compared during the same life stage (e.g., all individuals become bolder when growing older due to, e.g., experience effects). The ontogeny of individuality has been well studied in domesticated animals (reviewed in Carere et al. 2005) but less so in other animals (e.g., Francis 1990). We suggest that ontogenetic effects may be particularly important in species with indeterminate growth. In fish, for example, it might pay younger smaller individuals to be shy and avoid predators, as opposed to older larger individuals that might be better off by being bold and competing for reproduction. Behavioral types might also be affected by state, and distinct behavioral types might appear due to comparing individuals from different states, whereas in fact, individuals from the same state show the same behavioral type (e.g., males are bolder and Many studies have found that seemingly unconnected behaviors are correlated into behavioral syndromes. These behavioral syndromes may be the consequence of interindividual variation in life-history strategies. Only few studies have investigated the role of behavioral syndromes in cooperatively breeding species, despite the fact that one would expect particular large variation in behavior due to the wealth of life-history decisions a cooperative breeder faces. In a longitudinal study, we repeatedly tested individuals of the cooperatively breeding cichlid Neolamprologus pulcher for exploration, boldness, and aggression and tested whether these behaviors were sex specific; whether they were interrelated; and whether they were connected to growth and to 2 major lifehistory decisions, helping, and dispersal. In both sexes, explorative behavior was correlated over time, even though after sexual maturity males increased their exploration rate. In both sexes, exploration, boldness, and aggression correlated when mature, and in females, helping behavior was part of the syndrome. No relationships with growth were detected. Helping and dispersal were related to each other in males, whereas females hardly dispersed. We suggest that the differences in the life histories between males and females (male dispersal vs. female philopatry) lead to the differences in behavioral types observed and also to the differences in the stability of the behavioral syndromes between the sexes. The links between dispersal and helping in males and the behavioral types and helping in females highlight the necessity to study multiple traits to understand the evolution and maintenance of variation in cooperative behavior. Key words: behavioral syndrome, Cichlidae, cooperative breeding, life history, Neolamprologus pulcher, ontogeny. [Behav Ecol 21:588–598 (2010)] Schürch and Heg • Life history and behavioral type in Neolamprologus pulcher siveness should be detectable among subordinates in cooperative breeders. We tested these ideas in a longitudinal study in the lab using the cichlid Neolamprologus pulcher. In an earlier study on the cooperatively breeding cichlid N. pulcher, Bergmüller and Taborsky (2007) have already found consistent individual variation in helping, exploration, boldness, and aggression in the short term. However, the ontogeny, potential differences between the sexes, and their relationships to helping, dispersal, and growth could not (...truncated)