The power of oral and nasal calls to discriminate individual mothers and offspring in red deer, Cervus elaphusстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 19 сентября 2015 г.
Аннотация:Background
Mother-offspring recognition is critically important for the survival of the young for many mammal and bird taxa. In most species, acoustical cues are crucial for recognition. Studies of a few species of ungulates showed that potential for individual recognition may differ between nasal and oral contact calls.
Results
Vocalizations of 28 hinds and 31 calves of farmed Iberian red deer (Cervus elaphus hispanicus) were examined with discriminant function analyses (DFA) to determine whether acoustic structure of their oral and nasal contact calls encodes information about the caller’s identity. Contact calls were elicited by brief separation of individually identified animals by a distance over 10 m or by a bar fence. Both oral and nasal calls of both hinds and calves showed high potential to discriminate individuals. In hinds, individuality was significantly higher in the oral than in the nasal calls, whereas in calves, individuality was equally well expressed in both oral and nasal calls. For calves, the maximum fundamental frequency was higher and the duration was longer in oral calls than in nasal calls. For hinds, the maximum fundamental frequency and the duration were indistinguishable between oral and nasal calls. Compared to the pooled sample of oral and nasal calls, separate oral or nasal call samples provided better classifying accuracy to individual in either hinds or calves. Nevertheless, in both hinds and calves, even in the pooled sample of oral and nasal calls, the degree of individual identity was 2-3 times greater than expected by chance. For hinds that provided calls in both years, cross-validation of calls collected in 2012 with discriminant functions created with calls from 2011 showed a strong decrease of classifying accuracy to individual.
Conclusions
These results suggest different potentials of nasal and oral calls to allow the discrimination of individuals among hinds, but not among red deer calves. Further playback study is necessary to confirm effects of these differences between call types on mother-offspring recognition. The high potential of individual recognition even with the pooled sample of oral and nasal calls allows mother and young to remember only one set of acoustic variables for mutual vocal recognition. Also, these results indicate poor between-year stability of individual characteristics of hind oral and nasal calls. Given that instability between years, acoustic cues underlying mother-offspring discrimination would require updating each calving season.