1,721,134 research outputs found
Nightingales respond more strongly to vocal leaders of simulated dyadic interactions
No full textAlthough vocal interactions in songbirds have been well studied, little is known about the extent to which birds attend to their conspecifics' interactions. Attending to others' interactions can provide valuable information since vocal interactions are often asymmetrical and can reflect differences in the state or quality of the signallers. Playback experiments with simulated dyadic interactions showed that male territorial nightingales (Luscinia megarhynchos) attend to asymmetries in interactions and respond more strongly to rivals that overlap the songs of their counterpart. In order to test if nightingales respond differently to two interacting rivals that are alternating songs asymmetrically (with leader-follower roles), we simulated an interaction using a dual-speaker design. Subjects discriminated between the simulated singing strategies and responded more intensely at the loudspeaker playing the preceding songs. This suggests that individuals whose songs precede in an interaction when there is no acoustic overlap are perceived as more serious rivals. Intense responses to the preceding songs compared with intense responses to the overlapping (non-preceding) songs in a previous study also indicate that discrimination is not the result of one specific proximate cue such as greater attention to the first- or last-heard stimulus. Thus, these results provide further evidence that by listening to asymmetries in conspecifics' vocal interactions, receivers can obtain valuable information on their relative differences.</p
The duration of alarm- and territorial defence calls alters receiver response in Eurasian magpies
No full textAnimals use vocal signals to provide information across a wide range of contexts. However, it is more complex to identify the information content when the same vocalizations are produced in different contexts, such as against predators and conspecific competitors. This raises the question whether information about the caller or context can be coded in relatively subtle variation within the call type and whether receivers respond differentially to such variation. Using playbacks of the general ‘chatter’ alarm call of Eurasian magpies (Pica pica), we tested whether or not territorial magpies respond differently to variation in call duration and rate. We show that magpies responded acoustically faster to chatters of longer duration, which may signal a greater motivation or urgency of territorial intruders. Alternatively, a delay in chatter response to shorter calls may reflect a period of hesitation and risk avoidance. Interestingly, magpies did not approach the loudspeaker more closely in response to longer calls and the total chatter response did not differ either. This suggests that after the short initial response, the persistence of the signal over time as well as visual information on the level or type of danger become essential for more differentiated response behaviours. Taken together, our results show that magpies perceive and respond differentially to variation in alarm call duration, suggesting that such variation encodes meaningful information
Microgeographic variation, habitat effects and individual signature cues in calls of chiffchaffs Phylloscopus collybita canarensis
No full textVariation of signals is a widespread feature in animal communication. Signals usually vary among signallers and in some cases vary across geographic areas. Individual variation provides the basis for individual recognition and thus has important implications for social interactions. Microgeographic variation can reveal insights into patterns of dispersal and into timing and mechanism of acquisition or development of behavioral traits. In addition, it may reflect adaptations of signals to the transmission characteristics of local habitat types. In song birds these kinds of variation have been documented in particular for male song. Here, we examined individual signature cues, site-specific variation, and variation among habitat types in tonal contact calls of 26 chiffchaffs, Phylloscopus collybita canarensis, recorded on two Canary islands. Multiparametric analyses of calls and subsequent discriminant function analyses revealed clear individual differences as well as microgeographic variation in call structure. Call structures differed not only between islands but also among the different locations on Tenerife, indicating that individuals on the same island do not share the same call, as suggested earlier. Calls recorded in different types of habitat, however, did not differ in structure as predicted by the 'acoustic adaptation hypothesis'. The findings indicate that individual recognition may be possible on the basis of calls and they contribute to the understanding of development of behavioural trails in relation to life history patterns such as the timing and pattern of dispersal.</p
Stone-assisted drumming in Western chimpanzees and its implications for communication and cultural transmission
No full textChimpanzees ( Pan troglodytes ) communicate in complex ways, including sounds produced by hand and foot drumming on trees, often combined with loud vocalizations. Recently, a puzzling stone throwing behaviour at trees was observed, resulting in stone piles at tree buttresses. It is a rare case of tool used for communication in animals and suggested to function like buttress drumming in long-distance communication and male displays. We tested this hypothesis by determining the behavioural dynamics in comparison to hand and foot tree buttress drumming in Western chimpanzees in Boé, Guinea Bissau. Using camera traps, we show that in 78% of cases, stones were picked up at trees, not leading to further stone accumulation beyond the already existing stone piles. Stone-assisted and hand and foot drumming occurred separately or were combined in similar behavioural contexts in apparent long-distance communication and highly aroused behavioural contexts. Yet, immediately before stone drumming, chimpanzees swayed less and pant-hooted more while afterwards pant-hooting less compared to the other contexts, suggesting a separate motivation and/or function for stone-assisted drumming. It suggests this unique stone-based activity has its own signal value, separate from hand/foot buttress drumming and, considering the spatial variation, might be culturally transmitted
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
