Ecological and evolutionary consequences of selective interspecific information use

Recent work has shown that animals frequently use social information from individuals of their own species as well as from other species; however, the ecological and evolutionary consequences of this social information use remain poorly understood. Additionally, information users may be selective in their social information use, deciding from whom and how to use information, but this has been overlooked in an interspecific context. In particular, the intentional decision to reject a behaviour observed via social information has received less attention, although recent work has indicated its presence in various taxa. Based on existing literature, we explore in which circumstances selective interspecific information use may lead to different ecological and coevolutionary outcomes between two species, such as explaining observed co-occurrences of putative competitors. The initial ecological differences and the balance between the costs of competition and the benefits of social information use potentially determine whether selection may lead to trait divergence, convergence or coevolutionary arms race between two species. We propose that selective social information use, including adoption and rejection of behaviours, may have far-reaching fitness consequences, potentially leading to community-level eco-evolutionary outcomes. We argue that these consequences of selective interspecific information use may be much more widespread than has thus far been considered.     

New behavioural trait adopted or rejected by observing heterospecific tutor fitness

Animals can acquire behaviours from others, including heterospecifics, but should be discriminating in when and whom to copy. Successful individuals should be preferred as tutors, while adopting traits of poorly performing individuals should be actively avoided. Thus far it is unknown if such adaptive strategies are involved when individuals copy other species. Furthermore, rejection of traits based on tutor characteristics (negative bias) has not been shown in any non-human animal. Here we test whether a choice between two new, neutral behavioural alternatives-breeding-sites with alternative geometric symbols-is affected by observing the choice and fitness of a heterospecific tutor. A field experiment replicated in four different areas shows that the proportion of pied flycatcher females matching the choice of the tit tutor consistently increased with increasing number of offspring in the tit nest, to the extent of nearly complete prevalence in one of the areas when tit fitness was highest. Notably, all four replicates demonstrate rejection of the behaviour of lowest-fitness tutors. The results demonstrate both acquisition and avoidance of heterospecific behavioural traits, based on the perceived (lack of) tutor fitness. This has potential implications for understanding the origin, diversity and local adaptations of behavioural traits, and niche overlap/partitioning and species co-occurrence.     

Interspecific social learning: novel preference can be acquired from a competing species

Nongenetic transmission of behavioral traits via social learning allows local traditions in humans, and, controversially, in other animals [1-4]. Social learning is usually studied as an intraspecific phenomenon (but see [5-7]). However, other species with some overlap in ecology can be more than merely potential competitors: prior settlement and longer residence can render them preferable sources of information [8]. Socially induced acquisition of choices or preferences capitalizes upon the knowledge of presumably better-informed individuals [9] and should be adaptive under many natural circumstances [10, 11]. Here we show with a field experiment that females of two migrant flycatcher species can acquire a novel, arbitrary preference of competing resident tits for a symbol attached to the nest sites. The experiment demonstrates that such blind acquisition of heterospecific traits can occur in the wild. Even though genetic variation for habitat preferences exists in many taxa [12] and overlap between bird species likely induces costs [13], this result shows that interspecific social learning can cause increased overlap in nest-site preferences. Conventional, negative species interactions push ecological niches of species apart, but the use of competing species as a source of information counters that force and may lead to convergence.     

Mechanisms and fitness effects of interspecific information use between migrant and resident birds

Interactions with potential competitors are an important componentof habitat quality. Due to the costs of coexistence with competitors,a breeding habitat selection strategy that avoids competitorsis expected to be favored. However, many migratory birds appearto gain benefits from an attraction to the presence of residentbirds, even though residents are assumed to be competitivelydominant. Thus far the mechanisms of this habitat selectionprocess, heterospecific attraction, are unknown, and the consequencesfor resident birds of migrant attraction remain untested. Throughheterospecific attraction, migrants may gain benefits if thedensity or territory location of residents positively reflectshabitat quality, and/or they gain benefits through increasedfrequency of social interactions with residents in foragingor predator detection. In this experiment, we examined the reciprocaleffects of spatial proximity on fitness-related traits in migrantpied flycatcher (Ficedula hypoleuca) and resident great tit(Parus major) by experimentally forcing them to breed eitheralone or in close proximity to each other. Surprisingly, greattits bore all the costs of coexistence while flycatchers wereunaffected, even gaining slight benefits. In concert with anearlier study, these results suggest that flycatchers use titsas information about good-quality nest-site locations whilebenefits from social interactions with tits are possible butless important. We suggest that utilizing interspecific socialinformation may be a common phenomenon between species sharingsimilar resource needs. Our results imply that the effects ofinterspecific information use can be asymmetric and may thereforehave implications for the patterns and consequences of speciescoexistence.     

Observed heterospecific clutch size can affect offspring investment decisions

Optimal investment in offspring is important in maximizing lifetime reproductive success. Yet, very little is known how animals gather and integrate information about environmental factors to fine tune investment. Observing the decisions and success of other individuals, particularly when those individuals initiate breeding earlier, may provide a way for animals to quickly arrive at better breeding investment decisions. Here we show, with a field experiment using artificial nests appearing similar to resident tit nests with completed clutches, that a migratory bird can use the observed high and low clutch size of a resident competing bird species to increase and decrease clutch size and egg mass, accordingly. Our results demonstrate that songbirds can discriminate between high and low quantity of heterospecific eggs, and that social information can have long-term physiological consequences affecting reproductive strategies. Such behaviour may help animals to better adapt to changing environments and lead to convergent traits with competitors.