Vocal individuality of Little Spotted Kiwi (Apteryx owenii)

Abstract

The ability to identify individuals by call is particularly important for monitoring cryptic or nocturnal species. It provides key benefits in conservation management, such as allowing correction of biases in censuses and monitoring individual survival. Call surveys are a key tool in conservation of kiwi (Apterygidae), yet individuality of calls has previously been assessed in just one of the five species, the Brown Kiwi (formerly North Island Brown Kiwi, Apteryx mantelli). We have made the first test of whether Little Spotted Kiwi (Apteryx owenii; LSK) can be individually identified by call. Three classification methods (discriminant function analysis, support vector machines and statistical classifiers) were used to assign identity from either call or syllable variables. Using syllables, classification was significantly better than expected by chance for both males and females. Individual LSK can therefore be identified acoustically, suggesting that vocalisations may be used for conspecific identification. Classifier performance was worse using call variables, with no better than chance assignment for females and low accuracy for males. Significant differences in classification ability between the sexes support the hypothesis that the function of calls of male and female LSK differ. Furthermore, identification by call was much less reliable in LSK than in the more genetically diverse Brown Kiwi. This indicates that call diversity may be related to genetic diversity in kiwi, which, if confirmed, could provide a powerful conservation tool for rapid assessment of genetic differences among populations of these threatened species.