CONCEPTS & SYNTHESIS EMPHASIZING NEW IDEAS TO STIMULATE RESEARCH IN ECOLOGY Ecology, 00(0), 0000, pp. 000–000 Ó 0000 by the Ecological Society of America SOCIAL INFORMATION USE IS A PROCESS ACROSS TIME, SPACE, AND ECOLOGY, REACHING HETEROSPECIFICS 1,4 2,5 1 3 JANNE-TUOMAS SEPPA¨NEN, JUKKA T. FORSMAN, MIKKO MO¨NKKO¨NEN, AND ROBERT L. THOMSON 1Department of Biological and Environmental Science, POB 35, FIN-40014, University of Jyva¨skyla¨, Jyva¨skyla¨, Finland 2Department of Animal Ecology, EBC, Uppsala University, Norbyva¨gen 18D, SE-752 36 Uppsala, Sweden 3Section of Ecology, Department of Biology, University of Turku, 20014 Turku, Finland Abstract. Decision making can be facilitated by observing other individuals faced with the same or similar problem, and recent research suggests that this social information use is a widespread phenomenon. Implications of this are diverse and profound: for example, social information use may trigger cultural evolution, affect distribution and dispersal of populations, and can involve intriguing cognitive traits. We emphasize here that social information use is a process consisting of the scenes of (1) event, (2) observation, (3) decision, and (4) consequence, where the initial event is a scene in such a process of another individual. This helps to construct a sound conceptual framework for measuring and studying social information use. Importantly, the potential value of social information is affected by the distance in time, space, and ecology between the initial observation and eventual consequence of a decision. Because negative interactions between individuals (such as direct and apparent competition) also depend on the distance between individuals along these dimensions, the potential value of information and the negative interactions may form a trade-off situation. Optimal solutions to this trade-off can result in adaptively extended social information use, where using information gathered some time ago, some distance away, and from ecologically different individuals is preferred. Conceivably, using information gathered from a heterospecific individual might often be optimal. Many recent studies demonstrate that social information use does occur between species, and the first review of published cases is provided here. Such interaction between species, especially in habitat selection, has important consequences for community ecology and conservation. Adaptively extended social information use may also be an important evolutionary force in guild formation. Complex coevolutionary patterns may result depending on the effect of information use on the provider of information. Key words: autocorrelation; habitat selection; heterospecific attraction; public information; social information; social learning. QUESTIONS ON SOCIAL INFORMATION USE This phenomenon, generally termed social informa- Organisms continuously face situations where a tion use or social learning, has attracted a lot of research interest in recent years and appears to be widespread decision has to be made with imperfect information across the animal kingdom (Danchin et al. 2004). Social and thus with uncertainty about the consequences of information use is an exciting topic for several reasons. that decision. Fortunately, fellow beings are usually It is a mechanism allowing cultural evolution—a faced with at least a similar conundrum, and the possible, potentially important, but often hotly debated decisions made by—and the repercussions for—these pathway of inheritance. Important aspects of a species’ individuals can be used as information to aid in one’s ecology, such as foraging, spatial distribution, and own decision-making process. dispersal, may be profoundly affected by social infor- mation use, leading to population-level consequences. Manuscript received 18 October 2006; revised 3 January Questions on the acquisition, processing, and usage of 2007; accepted 12 December 2006. Corresponding Editor: B. P. social information bring in intriguing cognitive issues in Kotler. 4 E-mail: janseppa@jyu.fi communication, social learning, and imitation. Studying 5 Present address: Department of Biology, University of a phenomenon linking such diverse aspects of evolu- Oulu, POB 3000, FI-90014 Oulu, Finland. tionary, behavioral, and cognitive ecology as well as JANNE-TUOMAS SEPPA¨NEN ET AL. Ecology, Vol. 00, No. 0 YNTHESIS &S FIG. 1. Schematic illustration of three linked sequences of information use. Alice observes (personal sample) the environment directly. Bob observes the publicly observable manifestation of Alice’s decision (social cue). Carol observes the consequence of Bob’s information use (vicarious sample). Not illustrated is the case of observing another’s broadcasted observation (evolved signal ONCEPTS or semantic communication). The hypothetical example underlines that even if the source accurately reflects resources at the time of C observation and the decision is correct in the light of that information, information value is not necessarily positive if the consequence is realized temporally, spatially, or ecologically far from the observation. evolutionary psychology and anthropology (Boyd and linked to an information use process of another Richerson 1985, Whiten and Ham 1992) is likely to yield individual (Fig. 1). This definition firmly connects the important, integrating insights. concept of social information to events and entities Recent reviews of social information use cover amenable to empirical research, and it invokes a natural foraging (Galef and Giraldeau 2001), performance of measure of the value of information: fitness. Also, a others and cultural evolution (Danchin et al. 2004), and categorization of the types of social information, if such implementing statistical decision theory (Dall et al. is sought, logically follows from this framework. 2005). The categorization (Zentall 2006) and strategies Recognizing the entire sequence instead of just the (Laland 2004) of acquisition of social information are sources or mechanisms in the process of social informa- better understood, but there is little agreement on central tion use provides novel insights. Importantly, informa- definitions and concepts of social-information use in tion use is necessarily an extended process in temporal, ecology. What is social information use exactly? Where, spatial, and ecological dimensions, and this is likely to how, and between whom is it expected to occur? Can and have far-reaching consequences. The second part of this should specific types of social information be distin- paper elaborates our view that the effect of autocorre- guished, and if so, what are they (Bednekoff 2005, Dall lation on the trade-offs between competition and 2005, Danchin et al. 2005, Lotem and Winkler 2005)? information use along temporal, spatial, and ecological The first part of this paper outlines the argument that dimensions can affect how social information is used. information use in general is a sequential process The extended nature of social information use can also (McNamara and Houston 1980, Dall et al. 2005), and determine what, and perhaps more importantly whom, social information use is formed when such a process is organisms should use as a source of social information. Month 2007 SOCIAL INFORMATION FROM HETEROSPECIFICS Plausibly, individuals of most animal species are uncertainty about the environment is reduced. In other constantly surrounded by diverse sights, sounds, and words, for information to have value, it must change the scents that mirror decisions of someone else, while some functioning of an organism in an evolutionarily relevant fewer scenes reveal the success of the decisions made. manner (Dall et al. 2005, Danchin et al. 2005). And, Colonial species aside, most of the observable events from a practical point of view, we can rarely perceive shall involve individuals of other species. We argue that information possessed by an animal until it alters its social information use is not necessarily restricted to a actions. It seems then that the most salient quantifica- conspecific setting and that heterospecifics are possible, tion of information for purposes of evolutionary ecology and sometimes the preferred, or the only, sources of is the difference in resulting fitness between the chosen information. In the third part of this paper we provide decision and the decision that would have been made the first brief review of the published cases of without the observation. This does not require the interspecific social information use. chosen decision to be an ‘‘adaptive response’’ (Jablonka Finally, we discuss the implications of our arguments. 2002) or lead to ‘‘a superior outcome’’ (Weinberger Ecological consequences of interspecific social informa- 2002). tion use have impact on community ecology and We suggest that in addition to ‘‘adaptive response’’ conservation. Adaptively extended social information decisions yielding increased fitness, information use can use gives rise to interesting evolutionary scenarios in also involve a decision that is ‘‘misinformed,’’ a phenology, social learning, and guild formation. Co- ‘‘gamble,’’ or ‘‘assured.’’ As long as consequences of a evolution between providers and users of information is decision have not been realized and there is uncertainty also conceivable, leading to arms races, or perhaps to a regarding the true state of the world, there also remains mutual ‘‘Information Market.’’ uncertainty (a probability distribution) of eventual DEFINING VALUE AND THE PROCESS OF INFORMATION USE