Chester Zoo

Do mating traits evolve ex situ, and should we care?

Chester Zoo - 24th Jul, 2023


Zoo conservation breeding programmes are an essential tool in conservation efforts. However, changes in animal behaviour over generations can impact the success of these programmes. 

Acoustic (vocal) communication plays an important role in a range of social behaviours in birds, including social cohesion, territory defence, and mate choice. In wild populations, a range of factors, from environmental differences to vocal learning, contribute to the formation of population specific dialects, where populations differ significantly in vocal behaviour. This, in turn, impacts responses, with birds responding more strongly to their local song dialect than those from other populations. Similar vocal change could occur in zoo populations, resulting in differences in vocalizations and responses between wild and zoo populations, as well as among zoo populations. 

This project aimed to answer two key questions; how vocal behaviour could change during conservation breeding programmes, and, whether these changes could impact the success of conservation programmes. We focused on the Java sparrow (Padda oryzivora), an endangered Estrildid finch common in zoos, as a model species. 

As social learning of vocalizations plays a role in dialect formation, it is important to understand the role of learning in song development. Java sparrows learn many parts of their vocalizations; song complexity, note acoustic structure, and temporal features of songs. However, learning is not perfect, songs of sons and their fathers differed across features. Vocal behaviour can also be influenced by other features associated with conservation breeding. Morphological differences between zoo and wild populations of Java sparrows may result in vocal divergence, as these traits are correlated in a number of other bird species. Significant human disturbance to the sound environment, indicated by altered soundscapes during COVID-19 closures, may also contribute to shifts in vocal behaviour for this species. As a result, population-level vocal divergence is likely during the conservation breeding of the Java sparrow. The formation of population specific dialects could impact social interactions in this species. Female birds showed preferences for familiar, over unfamiliar, songs. This could contribute to assortative mating based on song type, and affect pairing when bringing birds from multiple source populations together. 

Overall, these findings suggest that there is the potential for the evolution of vocal behaviour during conservation breeding of bird species. These changes may also impact conservation programmes due to their influence on individual’s behavioural responses. Moving forwards, the impacts of vocal behaviour on conservation efforts requires further investigation in this and other species and may be necessary to consider in species management plans. 

Work for this project was carried out by Rebecca Lewis as part of a PhD at the University of Manchester funded by the Natural Environment Research Council (NERC) and the Chester Zoo Conservation Scholars and Fellows Scheme. Sections of the project also received funding from the Daiwa Anglo-Japanese Foundation and the Japan Society for the Promotion of Science. 

This project won a Bronze Award in Research category of the BIAZA Awards 2023

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