Balancing past and present: how experience influences boldness over time in Eurasian perch

Current Zoology, 2017, 63(2), 159–164 doi: 10.1093/cz/zow043 Advance Access Publication Date: 31 March 2016 Article Article Balancing past and present: how experience influences boldness over time in Eurasian perch Gustav HELLSTRÖMa and Carin MAGNHAGENb a Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden and bDepartment of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden. Address correspondence to Gustav Hellström. E-mail: . Received on 16 December 2015; accepted on 9 March 2016 Abstract Adapting to fluctuating predation conditions is a challenge for prey. By learning through experience, animals may adjust their anti-predator behavior to better reflect current predation risk. Although many studies show experience of predation to alter prey behavior, little is known about how prey rely on such experience over time. By comparing boldness over different temporal scales between individuals of Eurasian perch, either experienced or naı̈ve of predators, we examine how risk is traded based on past and present experience. Differences in predator exposure during the first year of life were found to lead to differences in risk-taking behavior, even after the perch been kept in a predator-free environment for 9 months. However, the response to a potential predator was quickly readjusted after increased experience of current conditions. The results highlight how prey have to balance past experiences of predators against current threat levels. Key words: behavior, fish, learning, personality, predation, risk-taking. Prey animals frequently have to trade fitness-related behaviors, such as foraging, against the risk of predation (Lima 1998). Theory suggests adaptive anti-predator responses to reflect the intensity, duration, and variability of the predation risk (Helfman 1989; Lima and Bednekoff 1999), with the prey adjusting behavior on the basis of a reliable risk assessment (Bouskila and Blumstein 1992). Flexibility in anti-predation response can hence be advantageous, allowing prey to continually fine-tune behavior to match the experience of current predation condition. Changing behavior based on experience requires the ability to learn from events and situations, and to be able to act on gained knowledge for a certain amount of time (Shettleworth 2010). Depending on context, the time span an animal is affected by past experience may have adaptive significance (Kramer and Golding 1997; Ferrari 2010a). In fluctuating environments, acting on the most recent information is likely more relevant than relying on old information recalled from prior experience. For example, rapid and unpredictable spatial change in food distribution may disfavor foraging individuals restrained by past experience, and favor individuals more guided by current experience (Cuthill et al. 1990; Warburton 2006). Likewise, knowledge that has relevance during C The Author (2016). Published by Oxford University Press. V extended periods should be retained by the animal for longer time. For example, in salmon, information related to homing is obtained at a young age and then remembered throughout the entire life without the need for reinforcements (Dittman et al. 1996). Little is known about how prey depend on learned anti-predator behavior over time (Kelly and Magurran 2006; Ferrari et al. 2010a). One may argue that learned anti-predator responses should be retained for longer time than, for example, learned knowledge regarding food-patch profitability, as failing to respond correctly to a predator may lead to death of the prey (Ferrari et al. 2010a). However, for most prey, predation risk varies greatly over time and space (Lima and Bednekoff 1999), as well as changes as prey gets larger and more experienced with age (Lundvall et al. 1999; Magnhagen and Borcherding 2008). Under such conditions, being too guided by prior predation experiences may result in suboptimal anti-predator responses and in the end potential loss of fitness, for example, by being too risk-averse the time spent foraging may decrease (Godin and Smith 1988; Lima and Dill 1990; Sih 1992). In fish, a general response to predation risk has been thought largely innate, allowing even young fish to correctly avoid predation without any need of prior experience (Kelly and Magurran 2003). Today, we know that fish also learn to recognize and respond to 159 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact 160 predators, either via direct experience, or through associative or social learning (Brown and Laland 2003; Kelly and Magurran 2006). One can assume that a constant revision of learned anti-predator behavior would be adaptive for a prey, making it able to adjust the intensity of the response to reflect the most recent learning experience (Ferrari et al. 2010a). In this study, we investigate the influence of past and current experience on risk-taking behavior in Eurasian perch Perca fluviatilis. We are using perch from the same population that had either been living in its natural environment, with a high density of cannibalistic perch, or been raised from hatching in a pond without predators. The perch are tested for boldness immediately after capture or after spending 9 months in tanks. Short-term behavioral change occurring during observations and between repeated runs was also monitored and compared. Materials and Methods Background The study was conducted on Eurasian perch collected from lake Fisksjön, a 0.75-ha mesotrophic lake close to Umeå (63 470 N; 20 170 E), Sweden. Fisksjön has a dense population of small perch with stunted growth, which creates a high cannibalistic predation pressure on the young-of-the-year (YOY) juvenile perch in the lake (Persson et al. 2003; Magnhagen 2006; Magnhagen and Borcherding 2008). Earlier studies, investigating Fisksjön and other lakes, have correlated predation pressure with perch behavior, and concluded that YOY perch from Fisksjön are less bold compared with perch from lakes with lower cannibalistic predation pressure (Magnhagen 2006; Magnhagen and Borcherding 2008). Magnhagen and Borcherding (2008) also concluded that such behavioral differences are not likely a consequence of selective predation mortality, but of fish adjusting behavior based on current predation conditions. Using a common garden approach, Hellström and Magnhagen (2011) found Fisksjön perch reared in predator-free environment to be significantly bolder than wild perch, indicating that boldness phenotype in these perch to a large extent is shaped by experience, rather than being inherited. This was further reinforced by Magnhagen et (...truncated)