Dialect formation in fragmented populations of the endangered North Island kokako (Callaeas wilsoni)

The role of behavioural ecology in the conservation of species and biodiversity remains poorly understood. Observational and experimental studies of bird song, using a biogeographic approach, provide an opportunity to address this issue. Here I test hypotheses on the emergence and divergence of song cultures related to historical as well as more recent population fragmentation events. The North Island kōkako (Callaeas wilsoni) is a duetting songbird endemic to New Zealand that was once widespread but, due to habitat loss and introduced predators, has become endangered. These birds are sedentary and monogamous with poor flying abilities. Therefore, all of the c. 1500 surviving individuals are marooned in 13 scattered surviving populations and 11 translocated populations. The historical fragmentation of populations, the kōkako’s territorial nature and capacity to learn songs, and the establishment of new populations through translocation make this species a good candidate for studies on the emergence of song cultures, social divergence and landscape effects on conservation from a behavioural perspective. Song sharing and comparisons of acoustic characteristics were used to reconstruct associations of song traditions and acoustic traits at both macrogeographic and microgeographic levels in the six largest surviving populations of kōkako (Chapter 2 and 3). Distinct song cultures or dialects were discovered in all populations examined. However, patterns of vocal similarity observed were not correlated with historical fragmentation patterns or linear geographical distance (Chapter 2). Instead, rapid vocal drift following fragmentation and isolation as well as founder effects linked to population contraction may explain current macrogeographic song variation (Chapter 3). Nevertheless, a fragmentation effect on song similarity, generating song repertoire divergence, was observed at a microgeographic scale within discontinuous populations (Chapter 2). In addition, juvenile dispersal across portions of tenuously connected habitat, which have strikingly different song cultures, suggests that kōkako learn songs after dispersal (Chapter 2). Post-dispersal learning may explain the lack of consistency between dialect membership and genetic relatedness among surviving populations. Dialect formation may occur as different cultural trajectories are forged by fragmentation and isolation; subsequent song convergence may then occur due to social selection or chance events. The effects of population size on song attributes, repertoires and sharing, vocal versatility and syntactical structure were examined within the six largest natural populations, as well as two translocated populations of kōkako (Chapter 3). Repertoire size, song diversity and the predictability of syntactical structure were positively correlated with population size. Song traditions and the rate of cultural evolution may depend on social interaction and population size, as the neutral model of song microevolution predicts. Smaller populations of kōkako, with reduced social stability under relaxed selection pressures, may resemble small colonizing groups undergoing founder effects and vocal drift leading to loose syntax, consistent with the ‘withdrawal of learning’ hypothesis. Furthermore, social modulation of vocal behaviour and song traditions are discussed in the context of reproductive success and adaptation to differing social conditions as in the case of translocation events (Chapter 3). Recently isolated translocated populations exhibit remarkable acoustic divergence and reduced song sharing with the corresponding source population (Chapter 4). Translocated populations showed relatively low song diversity and increased song sharing as well as acoustically distinct song features. To investigate how meaningful this vocal divergence was for individuals in source and translocated populations, a reciprocal playback experiment was performed to examine vocal and approach responses to simulated local and non-local intruders. Responses to simulated intruders differed among populations but there was little evidence of discrimination based on stimulus type. The degree of song divergence (i.e., repertoire and acoustic features) and vocal response to playback relative to the source population was greater in an older translocated population than a more recently translocated population (Chapter 4). Consistent with the consequences of founder effects and vocal drift, these results demonstrate that kōkako populations vocally diverge in isolation following the establishment of a population with a vocal subset and subsequently a different cultural trajectory (in accordance with the ‘withdrawal of learning’ hypothesis). Cultural erosion in small translocated populations may affect their viability as reduced vocal virtuosity can be associated with a reduced capacity for territory defense and mate attraction, and consequently low reproductive success. Song divergence can ultimately have important implications for our understanding of the evolution of animal societies and our ability to conserve animal populations

Conservation implications of song divergence between source and translocated populations of the North Island Kōkako

1. Translocation of individuals from healthy source populations to newly colonize or recolonize suitable habitat is a vital tool for the conservation of a species. Demographic, genetic and landscape factors, but also acoustic signals and cultural factors, will all affect translocation success. 2. We investigated variation in song, and response to song, of the endangered North Island kōkako Callaeas wilsoni (Bonaparte 1850) in New Zealand in two translocated populations and their source population. 3. We found significant vocal variation between the source population and both translocated populations, the latter of which had reduced repertoire sizes and increased repertoire sharing, as well as structurally different song elements of higher frequency and shorter duration. 4. Despite the song divergence and clear variability in the nature and level of response among populations, we did not find any evidence for discrimination against nonlocal song in our reciprocal playback experiments. 5. Synthesis and applications. Vocal divergence and reduced variability in translocated populations suggest founder effects or reduced social interaction rates. The variation could be viewed as cultural erosion and may undermine translocation success. Persistence of response to playback, despite vocal divergence, suggested that social restrictions on gene flow require at least a few decades of separation after translocation. The decision to translocate individuals of threatened species is becoming a more common tool for species conservation world-wide. We argue that it is important to take vocal variation into account during such management decisions as it may affect success of establishment and persistence of translocated populations

Does ‘acoustic anchoring’ reduce post-translocation dispersal of North Island robins?

Context: Animal translocations are an important conservation tool; however, post-release dispersal can hinder successful population establishment. Playback of conspecific song attracts dispersing individuals in some species, although its application following animal translocation has yet to be rigorously investigated. Aims: To determine whether conspecific song can be used as an ‘acoustic anchor’, we adopted an experimental approach during the translocation of 60 North Island robins (Petroica longipes). Methods: At one of two release locations, we broadcast song at natural rates from four speakers (4 h per morning), for 9 days following release; we set the second release location as a control where identical conditions were established but no playback occurred. To assess the impact of playback, we monitored speaker and control locations, surveyed tracks around the release areas, and radio-tracked robins over nine playback days and an additional 9 days. Key results: Most robins left both immediate release areas; however, our results showed that (1) more robins (6 birds on 14 of the 18 days), in particular females (3 birds), approached the playback location than the ‘flagged’ control location (3 male birds on 5 of the 18 days), (2) individual robins returned to the playback location repeatedly, unlike those at the control site, and (3) robins also visited the playback location longer after playback than they did silent control locations. In contrast, radio-telemetry data from five robins suggested that general dispersal was not influenced by playback. Two radio-tracked females moved over long distances (some to >3 km from their release location), whereas two radio-tracked males remained relatively close to the release sites. Conclusions: We demonstrated a short-term attraction effect of playback over a period of several weeks for some birds, particularly females. In contrast, we detected fewer birds over a shorter period at the silent control release site, where no females were detected. However, long-term monitoring at both sites suggested that the effect of playback on reducing post-release dispersal was transitory. Implications: The lack of a clear and lasting effect of acoustic anchoring on dispersal in the present study has provided information on the limited utility of song playback as a conservation management tool for this species. Consideration of the species’ ecology and suitability for ‘acoustic anchoring’ must be made before playback is employed as a conservation measure to reduce excess post-translocation dispersal

Factors affecting post-release dispersal, mortality, and territory settlement of endangered kokako translocated from two distinct song neighborhoods

Animal translocation success rate is generally low, with the causes of failure poorly understood without comprehensive and protracted monitoring. Here we examine the outcome of a translocation of endangered North Island kokako (Callaeas wilsoni) from two adjacent song neighborhoods in New Zealand, each with individual vocal traditions (c. 75% of phrases unshared) to a single release site. We conducted detailed radio-telemetry to monitor post-release dispersal over 50 days during four serial releases of 20 birds while we broadcast neighborhood-specific song around the release site. The birds moved substantial distances after release, however overall short-term release site dispersal was not as great as predicted by a random walk model, suggesting an attraction to playback and/or a reluctance to explore areas away from the release site. This apparent attraction was not specific to a given song neighborhood, however. Although the post-release mortality rate (22% over 31 days) was relatively high in this translocation, we did not detect an effect of sex, age, source origin, or duration of captivity on mortality. We show that habitat use during this acclimation period was disproportionate to availability – the birds’ preferred habitat was similar to that at the capture site. At least four pairs formed, with two and three confirmed breeding in the first and second seasons post-release respectively. Mate choice was non-assortative with respect to song neighborhood, revealing that reduced phrase sharing rates found in adjoining neighborhoods are not a barrier to pair formation. We compare this example with other kokako translocations and make recommendations for future translocations

ENGIU: Encuentro Nacional de Grupos de Investigación de UNIMINUTO.

El desarrollo del prototipo para el sistema de detección de Mina Antipersona (MAP), inicia desde el semillero ADSSOF perteneciente al programa de Administración en Seguridad y Salud en el trabajo de la UNIMINUTO, se realiza a partir de un detector de metales que emite una señal audible, que el usuario puede interpretar como aviso de presencia de un objeto metálico, en este caso una MAP. La señal audible se interpreta como un dato, como ese dato no es perceptible a 5 metros de distancia, se implementa el transmisor de Frecuencia Modulada FM por la facilidad de modulación y la escogencia de frecuencia de transmisión de acuerdo con las normas y resolución del Ministerio de Comunicaciones; de manera que esta sea la plataforma base para enviar los datos obtenidos a una frecuencia establecida. La idea es que el ser humano no explore zonas peligrosas y buscar la forma de crear un sistema que permita eliminar ese riesgo, por otro lado, buscar la facilidad de uso de elementos ya disponibles en el mercado