Motivation before meaning: motivational information encoded in meerkat alarm calls develops earlier than referential information.

Verhaltensbiologie, Zoologisches Institut, Universitat Zurich, Zurich, Switzerland.
The American Naturalist (Impact Factor: 4.55). 07/2007; 169(6):758-67. DOI: 10.1086/516719
Source: PubMed

ABSTRACT In contrast to historical assumptions about the affective nature of animal vocalizations, it is now clear that many vertebrates are capable of producing specific alarm calls in response to different predators, calls that provide information that goes beyond the motivational state of a caller. However, although these calls function referentially, it does not mean that they are devoid of motivational content. Studies on meerkats (Suricata suricatta) directly support this conclusion. The acoustic structure of their alarm calls simultaneously encodes information that is both motivational (level of urgency) and referential (predator specific). In this study, we investigated whether alarm calls of young meerkats undergo developmental modification and whether the motivational or the referential aspect of calls changes more over time. We found that, based on their acoustic structure, calls of young showed a high correct assignment to low- and high-urgency contexts but, in contrast to adults, low assignment to specific predator types. However, the discrimination among predator types was better in high-urgency than in low-urgency contexts. Our results suggest that acoustic features related to level of urgency are expressed earlier than those related to predator-specific information and may support the idea that referential calls evolve from motivational signals.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A long-standing question in animal communication is whether signals reveal intrinsic properties of the signaller or extrinsic properties of its environment. Alarm calls, one of the most conspicuous components of antipredator behaviour, intuitively would appear to reflect internal states of the signaller. Pioneering research in primates and fowl, however, dem-onstrated that signallers may produce unique alarm calls during encoun-ters with different types of predators, suggesting that signallers through selective production of alarm calls provide to conspecific receivers infor-mation about predators in the environment. In this article, we review evi-dence for such 'functional reference' in the alarm calls of birds based on explicit tests of two criteria proposed in Macedonia & Evans' (Ethology 93, 1993, 177) influential conceptual framework: (1) that unique alarm calls are given to specific predator categories, and (2) that alarm calls iso-lated from contextual information elicit antipredator responses from receivers similar to those produced during actual predator encounters. Despite the importance of research on birds in development of the con-ceptual framework and the ubiquity of alarm calls in birds, evidence for functionally referential alarm calls in this clade is limited to six species. In these species, alarm calls are associated with the type of predator encoun-tered as well as variation in hunting behaviour; with defence of reproduc-tive effort in addition to predators of adults; with age-related changes in predation risk; and with strong fitness benefits. Our review likely under-estimates the occurrence of functional reference in avian alarm calls, as incomplete application and testing of the conceptual framework has lim-ited our understanding. Throughout, therefore, we suggest avian taxa for future studies, as well as additional questions and experimental approaches that would strengthen our understanding of the meaning of functional reference in avian alarm calls. A central question in animal communication is what signals mean to the individuals producing them and to those receiving them. Two traditional views suggest that signals reflect either the affective or emotional state of the signaller, or its probable (immediate) future behaviour (Smith 1977; Marler et al. 1992), with addi-tional signal meaning dependent upon the contextual cues surrounding vocal production. Rather than reflecting the signaller's internal state, vocalizations
    Ethology 01/2013; 119:449-461. · 1.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Social living goes hand in hand with communication, but the details of this relationship are rarely simple. Complex communication may be described by attributes as diverse as a species' entire repertoire, signallers' individualistic signatures, or complex acoustic phenomena within single calls. Similarly, attributes of social complexity are diverse and may include group size, social role diversity, or networks of interactions and relationships. How these different attributes of social and communicative complexity co-evolve is an active question in behavioural ecology. Sciurid rodents (ground squirrels, prairie dogs and marmots) provide an excellent model system for studying these questions. Sciurid studies have found that demographic role complexity predicts alarm call repertoire size, while social group size predicts alarm call individuality. Along with other taxa, sciurids reveal an important insight: different attributes of sociality are linked to different attributes of communication. By breaking social and communicative complexity down to different attributes, focused studies can better untangle the underlying evolutionary relationships and move us closer to a comprehensive theory of how sociality and communication evolve.
    Philosophical Transactions of The Royal Society B Biological Sciences 07/2012; 367(1597):1869-78. · 6.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Most studies addressing the development of animal communication have focused on signal production rather than receiver decoding, and similar emphasis has been given to learning over nonlearning. But receivers are an integral part of a communication network, and nonlearned mechanisms appear to be more ubiquitous than learned ones in the communication systems of most animals. Here we review the results of recent experiments and outline future directions for integrative studies on the development of a primarily nonlearned behaviour-recognition of communication signals during ontogeny in a tropical frog. The results suggest that antecedents to adult behaviours might be a common feature of developing organisms. Given the essential role that acoustic communication serves in reproduction for many organisms and that receivers can exert strong influence on the evolution of signals, understanding the evolutionary developmental basis of mate recognition will provide new insights into the evolution of communication systems.
    The Scientific World Journal 01/2012; 2012:680632. · 1.73 Impact Factor

Full-text (2 Sources)

Available from
May 31, 2014