Basis For Individual Recognition Research Articles

Individual distinctiveness across call types of the southern white rhinoceros (Ceratotherium simum simum).

Individual distinctiveness in the acoustic structure of vocalizations provides a basis for individual recognition in mammals and plays an important role in social behavior. Within a species, call types can differ in individual distinctiveness, which can be explained by three factors, namely differences in the social function, the distance of the caller to the receiver, and the acoustic structure of the call. We explored the variation in individual distinctiveness across three call types (Grunt, Hiss, Snort) of the southern white rhinoceros (Ceratotherium simum simum) and investigated to what extent the abovementioned factors account for individual distinctiveness. Calls were recorded from 25 adult southern white rhinoceroses in six different zoos. We used three methods to compare the level of individual distinctiveness across call types, namely discriminant function analysis (DFA), potential for individual identity coding (PIC), and the information criterion (Hs). The three call types possessed an acoustic structure capable of showing individual variation to different extents. Individual distinctiveness was lowest for Snorts, intermediate for Hisses, and highest for Grunts. The level of individual distinctiveness of all three call types was lower than that previously reported for Pant calls of this species. Calls functioning to mediate intragroup social interactions had the highest individual distinctiveness. This highlights that a given communicative function and the need for individual discrimination during a social interaction have a major influence on the degree of individual distinctiveness.

Neural representation of face familiarity in an awake chimpanzee

Evaluating the familiarity of faces is critical for social animals as it is the basis of individual recognition. In the present study, we examined how face familiarity is reflected in neural activities in our closest living relative, the chimpanzee. Skin-surface event-related brain potentials (ERPs) were measured while a fully awake chimpanzee observed photographs of familiar and unfamiliar chimpanzee faces (Experiment 1) and human faces (Experiment 2). The ERPs evoked by chimpanzee faces differentiated unfamiliar individuals from familiar ones around midline areas centered on vertex sites at approximately 200 ms after the stimulus onset. In addition, the ERP response to the image of the subject’s own face did not significantly diverge from those evoked by familiar chimpanzees, suggesting that the subject’s brain at a minimum remembered the image of her own face. The ERPs evoked by human faces were not influenced by the familiarity of target individuals. These results indicate that chimpanzee neural representations are more sensitive to the familiarity of conspecific than allospecific faces.

Acoustic correlates of individuality in the vocal repertoire of a nocturnal primate (Microcebus murinus)

In mammals individual distinctiveness in vocalizations provides the basis for individual recognition and thus plays an important role in social behavior. In this study, first evidence is provided for a nocturnal primate that variation in individual distinctiveness across the vocal repertoire is to some extent determined by the context and the acoustic structure of the call types. Individual distinctiveness was investigated across call types in the gray mouse lemur, a nocturnal primate, living in a dispersed multi-male multi-female social system. To explore to what degree context and acoustic structure predict variations in individual distinctiveness, four major call types were examined (grunts, tsaks, short whistles, and trills). Call types differed in context and acoustic structure and were recorded under controlled experimental conditions. A discriminant function analysis revealed that all call types are individually distinct, but not to the same degree. The findings suggest that variations in individual distinctiveness can to some extent be explained by the context and the acoustic structure of the call types.

Microgeographic Variation, Habitat Effects and Individual Signature Cues in Calls of ChiffchaffsPhylloscopus collybita canarensis

Variation 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.

Parental calls and the approach behavior of young Canada geese: a laboratory study

A laboratory experiment was conducted to test whether parental calls of the Canada goose, calls A, B, and C, each recorded from a different individual goose, differentially affect the approach behavior of call A experienced and parental call naive goslings. Experience before with call A produced a greater number of approach responses to this call relative to the other calls and a parental call of the ring-billed gull. After training with a call, in the experiment paired with visual movement, individual parental calls can have distinct effects on the approach behavior of goslings. This process involving auditory and visual elements may be the basis of individual recognition in the Canada goose.

Acoustic basis for individual recognition by voice in the gannet.

A RECENT article by W. H. T.1 reviewed the general question of the perceptual basis for group organization by birds and other vertebrates. It pointed out that successful social organization of colonially nesting sea birds must in many cases depend on a capacity for mutual recognition at some distance, at least between mates and oalso between parents and young, perhaps extending to other members of the group. While many species of birds (such as gulls and ducks) have visual powers so acute that they are able to recognize individuals at distances of 50 m or more, it was nevertheless shown that auditory recognition of individuals by subtle voice characteristics also plays a part—sometimes major—in identification. Indeed, in some examples of gulls, penguins, auks and terns, the evidence suggests that audiovocal recognition is likely to be more effective in the difficult conditions of life in a dense breeding colony than is visual recognition. As an example, work on the sandwich tern (Sterna sandvicensis)2 has shown in some detail that the individual vocal patterns are constant and can be distinctively categorized in terms of a pattern of energy distribution expressed as frequency against time, which is so well shown by the spectrograph. This kind of pattern is, of course, what we ourselves hear as organized sounds with their characteristic temporal arrangement and tonal quality, as in speech or music.

The Basis for Individual Recognition By Voice in the Sandwich Tern (Sterna Sandvicensis)

Abstract 1. There is a considerable amount of observational evidence to show that in a number of bird species, especially colony-nesting sea birds, a bird's recognition of its mate and the mutual recognition of parent and young may, in certain circumstances, be based upon individual peculiarities of voice. However, with the exception of a preliminary account of the matter in the Guillemot, (Uria aalge), there is no analytical evidence to support these conclusions. 2. The Sandwich Tern (Sterna sandvicensis) provides good opportunity for study of one aspect of this problem, namely the individual distinctiveness of the 'fish-call' of the returning parent bird. Different individuals were recorded and the results analysed by sound spectrograph. 3. The fish-call is shown to be composed of three segments of sound; each segment displaying individual characteristics of duration, fine structure, pitch etc. The overall relations between them, the "patterning" of the call, is also shown to be characteristic. 4. The extent to which these separate individual characteristics are recognised as distinctive by birds themselves has not been investigated but it is clear that if the fish-call is to be used as an effective means of individual recognition in a large colony the patterning of the call (in the sense of the 'gestalt' or the overall relationship of the component parts) must play a major role.